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In its most extreme forms, aggression is human tragedy unsurpassed. Hopes that the horrors of World War II and the Holocaust would produce a worldwide revulsion against the taking of another human's life, resulting in the end of genocidal practices and a reduction in homicide rates, have been dashed by the realities of increasing homicide and genocide in the last half of the twentieth century. The litany of genocidal events is both long and depressing, including major massacres in Uganda, Cambodia, Rwanda, Burundi, Zaire, Bosnia, Serbia, Croatia, and Herzegovina, among others. Homicide rates have risen in a number of industrialized countries since World War II, most notably in the United States.

We have seen slight declines in the homicide rate in the United States during the 1990s. But despite six consecutive years of decreases, the 1997 homicide rate was still 133 percent of the 1965 rate, and 166 percent of the 1955 rate. For these and related reasons, interest in understanding the causes of aggression remains high, and there have been major advances in the social psychology of aggression.


Definitions have varied widely over time and across research domains. However, a consensus has emerged among most social psychologists studying human aggression about what constitutes "aggression" in general and what constitutes the major forms or "ideal types" of aggression. (See the following books for current definitions and perspectives on aggression: Baron and Richardson 1994; Berkowitz 1993; Geen 1990; Geen and Donnerstein 1998; Tedeschi and Felson 1994).

Basic Definitions. Aggression vs. Assertiveness vs. Violence. Human aggression is behavior performed by one person (the aggressor) with the intent of harming another person (the victim) who is believed by the aggressor to be motivated to avoid that harm. "Harm" includes physical harm (e.g., a punch to the face), psychological harm (e.g., verbal insults), and indirect harm (e.g., destroying the victim's property).

Accidental harm is not "aggressive" because it is not intended. Harm that is an incidental by-product of actions taken to achieve some superordinate goal is also excluded from "aggression" because the harm-doer's primary intent in such cases is to help the person achieve the superordinate goal and because the harm-recipient doesn't actively attempt to avoid the harm-doer's action. For example, pain delivered during a dental procedure is not "aggression" by the dentist against the patient.

In their scientific usages "aggressiveness" is very different from "assertiveness" even though the general public frequently uses these words interchangeably. When people say that someone is an "aggressive" salesperson they typically mean that he or she is assertive—pushy or confident or emphatic or persistent—but they do not truly mean "aggressive" unless, of course, they believe that the salesperson intentionally tries to harm customers. Similarly, coaches exhorting players to "be more aggressive" seldom mean that players should try to harm their opponents; rather, coaches want players to be more assertive—active and confident.

Violence, on the other hand, is a subtype of aggression. The term "violence" is generally used to denote extreme forms of aggression such as murder, rape, and assault. All violence is aggression, but many instances of aggression are not violent. For example, one child pushing another off a tricycle is considered aggressive but not violent. For example, one child pushing another off a tricycle is considered aggressive but not violent.

Affective vs. Instrumental Types of Aggression. "Affective" aggression has the primary motive of harming the target, and is thought to be based on anger. It is sometimes labeled hostile, impulsive, or reactive aggression, though these labels often carry additional meaning. When aggression is merely a tool to achieve another goal of the aggressor, it is labeled "instrumental" aggression. Most robberies are primarily instrumental, whereas most murders and assaults are affective. Similarly, Jack may hit Jim merely to obtain a desirable toy, a case of instrumental aggression. Jim may get angry and respond by hitting Jack in order to hurt him, a case of affective aggression.

Proactive vs. Reactive Types of Aggression. "Proactive" aggression occurs in the absence of provocation. It is usually instrumental, as when Jack hit Jim to get the toy. "Reactive" aggression is a response to a prior provocation, such when Jim retaliated. There is an asymmetrical relation between proactive and reactive aggression. Children who are high on proactive aggression usually are high on reactive aggression as well, but many children who are high on reactive aggression engage in little proactive aggression.

Thoughtful vs. Thoughtless Aggression. A more recent distinction among types of aggression concerns whether the aggressive act resulted from thoughtful or thoughtless (impulsive) psychological processes. In past work, instrumental aggression has usually been seen as thoughtful, involving the careful weighing of potential costs and benefits. But more recent work reveals that frequent use of aggression to obtain valued goals can become so automatized that it also becomes thoughtless. Affective aggression has usually been seen as thoughtless, but people sometimes consider various possible courses of action and decide that an angry outburst is the best way to achieve those goals. This distinction between thoughtful and thoughtless aggression has important implications for the development of and intervention in aggression.

Distinguishing among types of aggression is difficult because underlying motives and psychological processes must be inferred. Is Jim's angry attack on Jack purely anger-based, solely intended to harm Jack, or is there also some instrumental component? There is a growing realization that these ideal types of aggression rarely exist in pure form in the real world of human interaction. Indeed, a few scholars have argued that all aggression is instrumental, serving goals such as social control, public-image management, private-image management (i.e., self-esteem), and social justice. Nonetheless, most aggression scholars still find these distinctions helpful for theoretical, rhetorical, and application-oriented reasons.


The causes of aggression can be analyzed at two different levels: the proximal causes (in the immediate situation) and the more distal causes that set the stage for the emergence and operation of proximate causes.

Distal Causes: Biological Factors. Distal causes of aggression are those that make people ready and capable of aggression. Some are structural, built into the human species. Others are developmental, based on the particular environmental history of the individual, and result in individual differences in preparedness to aggress.

Genetics. In the broadest sense aggression is a species characteristic. That is, the human species has physical, cognitive, and emotional systems capable of intentionally inflicting harm on other humans. The genetic basis of aggression is easier to identify in nonhuman species, in which fighting behaviors can be produced by stimulating certain regions of the limbic system. Similar physiological systems exist in humans, but human behavior is much more complexly determined.

In the more usual sense genetic influences refer to individual differences in aggressiveness that are linked to genetic differences within the species. Human twin studies have yielded mixed results in estimates of the genetic contribution to human aggression. Miles and Carey (1997) did a meta-analysis (i.e., statistical review) on twenty-four "genetically informative" studies. Two important conclusions were: (1) up to 50 percent of variation in self- or parent-reported aggression was attributable to genetic effects; and (2) when aggressiveness was measured by careful observation of laboratory behaviors, the genetic effect disappeared and a strong family-environment effect emerged. These contradictory findings highlight the complexity of human aggression as well as the need for additional studies.

Mechanisms. Several biological mechanisms appear plausible as potential causes of individual differences in aggressiveness. Hormones (e.g., testosterone), neurochemicals (e.g., serotonin), attention deficit hyperactivity disorder, and general levels of arousal have all been linked to aggression. For example, Eysenck and Gudjonsson (1989) proposed that individuals whose nervous system is relatively insensitive to low levels of environmental stimulation seek out high-risk activities, including criminal ones, to increase their arousal.

But many biological effects on aggression are neither as strong nor as consistent as the general public believes. For example, testosterone is frequently cited as the explanation for male/female differences in violence rates, but the human literature on testosterone effects is far from clear. Testosterone levels in humans seems more closely linked to social dominance, which in turn may well influence aggression under some limited circumstances (Campbell, Muncer, and Odber 1997; Geary 1998).

Other psychological variables with links to aggression also appear to have some genetic basis. Empathy, behavioral inhibition, negative affectivity, extraversion, neuroticism, and psychoticism all have yielded evidence of some genetic heritability, and have obvious links to aggression. General intelligence may also link biological variation to aggressiveness; low intelligence increases the occurrence of frustrating failures and aversive conditions, which might increase the likelihood of a person developing an aggressive personality.

Distal Causes: Environmental and Psychological Factors. Numerous social, environmental, and psychological factors contribute to the development of habitual aggressiveness. Learning stands out as the most important factor of all.

Learning. Bandura's social-learning theory of aggression (1973) has been most influential. One key idea in this and all modern learning approaches is that much of human development is based on learning by observing how other people behave. Patterson, DeBaryshe, and Ramsey (1989) presented a detailed look at the maladaptive social-learning processes found in families of aggressive children. Among the key problems are parental use of poor disciplinary measures and inadequate monitoring of their children's activities. Similarly, Olweus (1995) has identified a number of child-rearing factors that are conducive to creating bullies: caretakers with indifferent attitudes toward the child; permissiveness for aggressive behavior by the child; and the use of physical punishment and other power-assertive disciplinary techniques.

Cognitive psychology has also been crucial in the present understanding of the aggressive personality, as can be seen in books by Berkowitz (1993) and Geen (1990), and in Huesmann's (1998) information-processing theory of aggressive personality development. In brief, humans begin learning from infancy how to perceive, interpret, judge, and respond to events in the physical and social environment. We learn perceptual schemata that help us decide what to look for and what we "see." We learn rules for how the social world works. We learn behavioral scripts and use them to interpret events and actions of others and to guide our own behavioral responses to those events. These various knowledge structures develop over time. They are based on the day-to-day observations of and interactions with other people: real (as in the family) and imagined (as in the mass media). For example, the long-term exposure to media violence can increase later aggressive behavior by influencing a variety of aggression-related knowledge structures. Such long-term media violence effects have been shown to be substantial in size and long lasting in duration (Huesmann and Miller 1994).

As knowledge structures develop, they become more complex, interconnected, and difficult to change. Developing knowledge structures are like slowly hardening clay. Environmental experiences shape the clay. Changes are relatively easy to make at first, when the clay is soft, but later on changes become increasingly difficult. Longitudinal studies suggest that aggression-related knowledge structures begin to harden around age eight or nine, and become more perseverant with increasing age.

People learn specific aggressive behaviors, the likely outcome of such behaviors, and how and when to apply these behaviors. They learn hostile perception, attribution, and expectation biases, callous attitudes, and how to disengage or ignore normal empathic reactions that might serve as aggression inhibitors.

The pervasiveness, interconnectedness, and accessibility of any learned knowledge structure is largely determined by the frequency with which it is encountered, imagined, and used. With great frequency even complex perception-judgment-behavior knowledge structures can become automatized—so overlearned that they are applied automatically with little effort or awareness. Frequent exposure to aggressive models is particularly effective in creating habitually aggressive people, whether those models are in the home, neighborhood, or mass media. Once the use of any particular knowledge structure has become automatized, it becomes very difficult for the person to avoid using it because the perceptions and behavioral impulses it produces seem to be based on "how the world really is."

Social Processes. Several common social processes contribute to disproportionate exposure to and learning of aggression-related knowledge structures. Low intellect (social or academic) creates excessive failures and frustration in a variety of developmental contexts. Low social intelligence, for example, leads to problems in interpersonal interactions, whereas low academic intelligence creates problems in school settings. Problems in either context typically lead to higher-than-normal levels of aggression, which lead to further frustrating encounters with parents, teachers, and peers. The resulting social ostracism often forces children to spend more time with other social misfits who also have highly aggressive behavior patterns. This "gang" can impede further intellectual development and reward additional antisocial tendencies.

Environments. Many social environments foster the development of an aggressive personality. Such factors include poverty; living in violent neighborhoods; deviant peers; lack of safe, supervised child recreational areas; exposure to media violence; bad parenting; and lack of social support. Growing up in a culture of fear and hate, as in many ethnic-minority communities around the world, may well be the most extreme version of an aggressive-personality–fostering environment, and may well account for the generation after generation of ethnic and religious hatreds and genocidal tendencies that occasionally erupt into genocidal wars (Keltner and Robinson 1996; Staub 1989, 1998). The perceptual knowledge structures modeled and explicitly taught in these contexts guarantee continued mistrust, misunderstanding, and hatred of key outgroups.

Even in its simplest form, poverty is associated with more frustrations, bad role models, and lack of good role models. Bad parenting includes several particularly common and damaging factors such as lack of parental attention, inconsistent discipline, harsh and abusive discipline, and inattention to nonaggressive efforts at problem solving by the child. Privation, victimization, and violence in a social milieu of long-standing ethnic/religious conflicts provide a powerful learning environment that is mightily resistant to change.

Short-term impoverishment, such as that brought on by a general decline in economic activity (e.g., a recession or depression), has been proposed as a causal factor in aggression directed against ethnic minorities. The dominant model is that the frustration engendered by such economic downturns leads to increased aggression against relatively powerless target groups. However, research casts considerable doubt on this hypothesis. For example, Green, Glaser, and Rich (1998) reanalyzed data on lynchings and data on "gay-bashing," and showed no evidence of short-term fluctuations in economic conditions and violence directed at minorities.

Child abuse and neglect. Child abuse and neglect itself are self-perpetuating problems. Abused or neglected children are particularly likely to become abusing and neglecting parents and violent criminal offenders. Children learn maladaptive beliefs, attitudes, and values from their abusive or neglectful parents (Azar and Rohrbeck 1986; Peterson, Gable, Doyle, and Ewugman 1997).

Proximate Causes: Individual Differences. The distal causes described in earlier sections set the stage for human aggression of various types. Proximate causes are those that are present in the current situation. One type of proximate cause consists of individual differences between people that have been created by their biological and social pasts. People differ widely in readiness for aggressing. These differences show considerable consistency across time and situations (Huesmann and Moise 1998).

Hostility Biases. Hostility biases have been identified in aggressive adults and children, some as young as six years. The hostile perception bias is the tendency of aggression-prone people to perceive social behaviors as more aggressive than do normal people, whereas the hostile expectation bias is the tendency of aggression-prone people to expect and predict others to behave relatively more aggressively (Dill, Anderson, Anderson, and Deuser 1997). The more widely studied hostile attribution bias is the tendency of aggression-prone people to attribute hostile intent to others' accidentally harmful behaviors. For example, Dodge (1980) had aggressive and nonaggressive children listen to a story about a boy who hurt another boy by hitting him with a ball. When asked, aggressive children attributed more hostile intent to the boy who threw the ball than did nonaggressive children.

Attitudes and Beliefs. Aggression-prone people hold favorable attitudes toward aggression, believing that aggressive solutions to problems are effective and appropriate. Aggressive thoughts and aggressive solutions come to mind quickly and easily. However, creating nonaggressive alternatives is particularly difficult for the aggressive person.

For example, Malamuth, Linz, Heavey, Barnes, and Acker (1995) found that sexually aggressive males hold relatively positive attitudes toward the use of aggression against women, believe in numerous rape myths, engage in more impersonal sex, and are likely to aggress against women in nonsexual contexts as well. Research (Anderson and Anderson 1999) reveals that sexually aggressive men are specifically aggressive only against women, in both sexual and nonsexual contexts, but are not unusually aggressive against other men.

Narcissism and Self-Esteem. The predominant view of the link between self-esteem and violence has been that low self-esteem contributes to high violence. However, research from several perspectives has demonstrated a very different pattern. Certain individuals with high self-esteem are most prone to anger and are most aggressive when their high self-image is threatened. Specifically, it is high self-esteem people who react most violently to threats to their self-esteem—if their high self-esteem is inflated (undeserved), unstable, or tentative. In other words, narcissists are the dangerous people, not those with low self-esteem or those who are confident in their high self-image (Baumeister, Smart, and Boden 1996; Bushman and Baumeister 1998; Kernis, Grannemann, and Barclay 1989).

Sex. Males and females differ in aggressive tendencies, especially in the most violent behaviors of homicide and aggravated assault. The ratio of male to female murderers in the United States is almost 10:1. Laboratory studies show the same type of sex effect, but provocation has a greater effect on aggression than does sex. Bettencourt and Miller (1996) used meta-analytic procedures and found that sex differences in aggression practically disappear under high provocation.

Men and women also appear to differ in what provokes them. Bettencourt and Miller showed that males are particularly sensitive to negative intelligence provocations whereas females are particularly sensitive to insults by a peer and to physical attacks. Geary, Rumsey, Bow-Thomas, and Hoard (1995) showed that males are more upset by sexual infidelity of their mates than by emotional infidelity, whereas the opposite pattern occurs for females. Buss and Shackelford (1997) showed similar sex differences in the effects of infidelity on mate-retention tactics, including use of violence.

Biology. Other biological differences that people bring with them to the current situation may also contribute to aggression, but as noted earlier many biological effects on aggression are neither as strong nor as consistent as the general public believes. For example, testosterone is frequently cited as the explanation for male/female differences in violence rates, but the human literature on testosterone effects is mixed.

Proximate Causes: Situational Factors. The second type of proximate causes of aggression consists of the situational factors currently present. Some of these factors are so powerful that even normally nonaggressive individuals can be made to behave aggressively.

Provocation. Most aggressive incidents can be directly linked to some type of perceived provocation. Some are direct and obvious, such as verbal insults and physical assaults. Some are less direct, as when an expected pay raise fails to materialize. Most murders and assaults in normal (i.e., nonwar) contexts are the result of provocations of one kind or another, usually in a series of escalatory provocations, threats, and counterthreats. Federal Bureau of Investigation data reveal that most murders in the United States occur during arguments among family, friends, or acquaintances. The tendency for stranger-based homicides to be relatively rare is even more pronounced in other industrialized cultures than in the United States. Frequently, the provocations involve sexual or emotional infidelity, or perceived insults to one's honor.

Frustration. Frustration is both an event and an emotional reaction. It occurs when something blocks the attainment or threatens the continued possession of a valued goal objective. For example, a supervisor's bad report may prevent a promotion, a spouse's infidelity may threaten the continued existence of a marriage, or a flood may destroy one's home. If the frustrating agent is another person, then the frustrating event is also a provocation.

The original form of the frustration-aggression hypothesis by Dollard, Doob, Miller, Mowrer, and Sears (1939) stated that: (1) all acts of aggression are the result of previous frustration; (2) all frustration leads to aggression. But some frustrations do not yield aggression, and some aggression is not the result of a prior frustration. Indeed, many contemporary scholars believe that if a frustrating event is fully justified, the frustrated person would show no residual inclination to aggress. However, Berkowitz (1989) claimed that even fully justified frustration can produce aggressive tendencies. This prediction was recently confirmed by Dill and Anderson (1995).

In a similar vein, Miller and Marcus-Newhall (1997) have shown that provocations can lead to increased aggressive tendencies against individuals who were not part of the frustrating event at all, a phenomenon typically labeled displaced aggression. Miller and Marcus-Newhall also suggest that such displaced aggression is increased if the displacement target provides a minor "triggering" provocation, and if the displacement target is a member of a disliked outgroup.

Incentives. Incentives are the rewards or benefits a person expects for having performed a particular action. Many situations in politics, the business world, and sports encourage aggression by their incentives. People often expect their chances of winning an election, getting a contract, or defeating an opponent to be enhanced by harming their competitor. Research on television violence has shown that seeing a character rewarded (or not punished) for aggressing increases subsequent aggression by the viewer more so than does unrewarded (or punished) television violence, presumedly by increasing the perceived incentive value of aggressive behavior.

The prototypical incentive-based example of individual aggression is the contract killer, who murders purely for money. The Iraqi assault and takeover of Kuwait, as well as NATO's subsequent attack on Iraq are clear examples of incentive-based institutional aggression (though other factors also clearly played a role). Contract murders account for only a small percentage of homicide totals, but they nicely illustrate the concept of relatively anger-free instrumental aggression.

Aversive Stimulation and Stress. Almost any form of aversive stimulation can increase the likelihood of aggression—noise, pain, crowding, cigarette smoke, heat, daily hassles, and interpersonal problems illustrate a few such aversive factors. When the cause of an aversive stimulus is an identifiable person, such as a smoker, these factors are also provocations. As such, they can increase aggression directed at the person identified as the provocateur, as well as against other "displaced" targets.

In cases where there is no identifiable human agent causing the aversive stimulation the effects on aggression are often less noticeable, but much research demonstrates their reality. The most studied of these effects, with relevant data gathered for over one hundred years, is the heat effect. Anderson and Anderson (1998) showed that a wide array of studies across time, culture, and method converge on the conclusion that hot temperatures increase aggressive tendencies. People who live in hotter cities have higher violent crime rates than those in cooler cities. This effect persists even when controlling for poverty, education, and culture. Violent crime rates are higher during hotter years, seasons, months, and days. When people are hot, they think more aggressive thoughts, feel more hostile, and behave more aggressively.

Alcohol and Drugs. Bushman (1993) reviewed studies on alcohol and drug effects on aggression, and found that central nervous system depressants increase aggression. Neither actual alcohol consumption nor the mere belief that one has consumed alcohol were individually sufficient to produce reliable increases in aggression, but when research participants believed they had consumed alcohol and had actually consumed alcohol, aggression increased. The exact mechanisms underlying these drug effects are not yet fully understood. Steele and Josephs (1990) proposed an "alcohol myopia" explanation, in which alcohol impairs key perceptual processes necessary to normal inhibitions against extreme and risky behavior. Bushman's review (1997) confirmed this view.

Aggression Cues. Objects or events associated with aggression in semantic memory can cue or "prime" aggression-related thoughts, affects, and behavior programs also stored in memory. For instance, seeing a gun can prime aggressive thoughts (Anderson, Benjamin, and Bartholow 1998) and increase aggressive behavior. This phenomenon, labeled the "weapons effect" by Berkowitz and LePage (1967), has been found in field and laboratory studies, in several different countries, with pictures of weapons and with real weapons.

As mentioned earlier, one prevalent source of aggressive cues in modern society is the mass media. Television shows, movies, and video games are filled with violence. Over 1,000 empirical comparisons, compiled by Paik and Comstock (1994) have conclusively demonstrated that even short-term exposure to media violence increases aggression. The immediate impact of viewing violent media is more pronounced for people with strong aggressive tendencies (Bushman 1995). Unfortunately, aggressive people also are the most likely to seek out violent media.

Many people in modern society believe that viewing aggression (e.g., on television) or behaving in a mildly aggressive way within protected environments (e.g., playing football) will reduce later aggressive behavior. This catharsis hypothesis, though, has been thoroughly debunked (Bushman, Baumeister, and Stack in press; Geen and Quanty 1977).

Opportunity. Some situations restrict opportunities to aggress; others provide "good" opportunities. Church service situations have many impediments to aggression—there are witnesses, strong social norms against aggression, and specific nonaggressive behavioral roles for everyone in attendance. Country and Western bars on Saturday nights present better opportunities for aggression, because many aggression facilitators are present: alcohol, aggression cues, aggression-prone individuals, males competing for the attention of females, and relative anonymity.

Removal of Self-Regulatory Inhibitions. One often-neglected facet of human aggression has garnered increased attention; the aggression inhibitions that normally operate in most people. Several different research groups have independently identified and discussed how these inhibitions are sometimes overridden (Bandura, Barbaranelli, Caprara, and Pastorelli 1996; Keltner and Robinson 1996; Staub 1989, 1998). Most people do not commit extreme acts of violence even if they could do so with little chance of discovery or punishment. Such self-regulation is due, in large part, to the fact that people cannot easily escape the consequences that they apply to themselves. Self-image, self-standards, and sense of self-worth—in other words moral standards—are used in normal self-regulation of behavior.

However, people with apparently normal moral standards sometimes behave reprehensibly toward others, including committing such actions as murder, torture, even genocide. Two particularly important mechanisms that allow people to disengage their normal moral standards involve moral justification and dehumanizing the victim. Common justifications for extreme and mass violence include "it is for the person's own good," or the good of the society, or that personal honor demands the violent action. These justifications can be applied at multiple levels, from a parent's abuse of a child to genocidal war. Dehumanizing the victim operates by making sure that one's moral standards are simply not applicable. War propaganda obviously fits this mechanism, but people also use this mechanism at an individual level. Potential victims are placed in the ultimate outgroup—one that has no human qualities.

The Escalation Cycle. Many proximate causal factors seem too trivial or weak to contribute to serious aggression. How can seeing a weapon, being uncomfortably hot, or watching a violent movie increase murder rates? The answer lies in the escalation cycle. As noted earlier, assaults and homicides do not typically result from one brief encounter or provocation. The parties involved usually know each other and have had a series of unpleasant exchanges. The final encounter may well begin as a relatively minor dispute, but one person escalates the level of aggression. The other person responds in kind and subsequently increases the aggressiveness of the next response. A shouting match can quickly become a shoving match, which can lead to fists, guns, and death. Seemingly trivial factors increase the likelihood of violence by increasing the accessibility of aggressive thoughts, affect, and behavioral acts at each turn of the escalation cycle.


The knowledge structure approach explains the difficulty of rehabilitating adults who repeatedly commit violent crimes, or of changing the genocidal climate of groups that have long histories of hate and violence. At the individual level, a lifetime of developing aggressive behavior scripts and automatized hostile perception, expectation, and attribution biases cannot be unlearned easily. However, this approach also reveals that preventing the development of an aggressive or genocidal personality is a more reasonable goal if appropriate steps are taken prior to full maturation.

Preventing and Treating Aggressive Personality. There are three main loci for preventing a child from developing into an aggressive adult. First, one can reduce exposure to events that teach aggressive behaviors or scripts. This would include direct modeling (e.g., by abusive or violent parents) as well as indirect modeling (e.g., exposure to media violence). Second, one can reduce exposure to events that teach that aggression is rewarding. For example, most media violence is highly rewarding for the perpetrator, especially when it is the protagonist who is committing the violence. Similarly, adult violence against children (e.g., by parents or school officials) appears highly rewarding to the child because the adult "wins" the encounter and there are no obvious costs to the adult for harming the child. Third, one can reduce exposure to events that teach hostile perception, expectation, and attribution biases. Once again, the entertainment media is one source of violence exposure that increases the perception that the world is a dangerous place. A heavy dose of media violence (e.g., television, movies, video games, music) can increase all three hostility biases. Witnessing high levels of violence in one's neighborhood also increases these biases.

At all three loci, reducing exposure to aggression-enhancing factors would seem much easier to do in the context of a normal and relatively nonviolent culture than in the context of a genocidal culture. Though the following statements focus on dealing with the aggressive personality, the general principles apply to dealing with the genocidal personality.

Furthermore, treating people who have already developed a strong and stable aggressive personality is much more difficult than preventing the development of such a personality. People with aggressive personalities must learn new nonhostile knowledge structures ranging from perceptual schemata through attributional ones to behavioral scripts. The knowledge structure approach outlined earlier explains why it is easiest to intervene successfully in younger children whose personalities are still malleable, harder to succeed with violent juvenile offenders and young abusive parents, and hardest of all to succeed with habitually violent adult criminals.

Child Abuse: Treatment and Prevention. Early intervention attempts relied primarily on intensive dynamic psychotherapy with the abuser, but this approach has repeatedly failed. Cognitive behavioral interventions have had much greater success, largely because they deal directly with the knowledge structure issues that are so important in this domain (Wolf 1994). This approach succeeds by teaching abusive caregivers to use nonaggressive child compliance techniques, personal anger control, and developmentally appropriate beliefs about childhood abilities.

Reducing Exposure to Aggressive Social Models. Reducing children's exposure to aggressive social models would reduce the percentage who grow up believing in and using aggressive tactics. One way of doing this is to reduce exposure to violent media, especially television and video games. The research literature on television violence has conclusively demonstrated that early and repeated exposure to violent television causes children to develop into aggressive adults. For example, kids who watch a lot of violent television at age eight are more likely to have criminal records at age thirty, even after statistically controlling for a variety of other relevant social variables. Research has suggested that exposure to violent video games has a similar effect.

Reducing other types of exposure to violent social models would also help. Reducing parental violence towards children, reducing the frequency and visibility of violence in children's neighborhoods, reducing violence in schools—including violence by school authorities in attempts to control children—would all have a positive impact on the overall level of aggressiveness in society.

Treating Violent Juvenile Offenders. Many treatments have been tried with violent juvenile offenders, including such things as "boot camps," individual therapy, "scared straight" programs, and group therapy; there is little evidence of sustained success for any of these approaches. One problem is that these standard approaches do not address the wide range of factors that contribute to the development and maintenance of violent behavior. However, there is evidence that treatment can have a significant beneficial impact on violent juvenile offenders (e.g., Simon 1998). Tate, Reppucci, and Mulvey (1995) drew attention to one approach with impressive results—the Multisystemic Therapy developed by Henggeler and Borduin (e.g., Henggeler, Schoenwald, Borduin, Rowland, and Cunningham 1998). Multisystemic Therapy is a family-based approach that first identifies the major factors contributing to the delinquent and violent behaviors of the particular individual undergoing treatment. Biological, school, work, peers, family, and neighborhood factors are examined. Intervention is then tailored to fit the individual constellation of contributing factors. Opportunities to observe and commit further violent and criminal offenses are severely restricted, whereas prosocial behavior opportunities (including studying school subjects, developing hobbies) are greatly enhanced, and are rewarded. Both the long-term success rate and the cost/benefit ratio of this approach have greatly exceeded other attempts at treating this population.

Adults. Attempts at treatment or "rehabilitation" of violent adults, usually done in the context of prison programs, have led to a general consensus of failure. However, several studies have yielded some evidence of a positive effect of treatment on the behavior of violent adults (e.g., Simon 1998). Rice (1997) reported that an intensive program for violent offenders cut recidivism rates in half for nonpsychopathic offenders. Unfortunately, the recidivism rate for psychopathic offenders was significantly increased by this particular treatment program.


Several controversial suggestions for social change emerge from the past forty years of research on human aggression. These suggestions, designed to decrease aggression and violence levels generally rather than to treat already-violent individuals, are controversial for political rather than scientific reasons. Research results clearly support each of them.

  1. Reduce exposure to media violence and other aggressive role models, especially for children and adolescents.
  2. Replace the use of corporal punishment with more positive child-control techniques.
  3. Reduce social rewards for aggressive activities, including those previously thought to be cathartic.
  4. Increase social rewards and social support for nonaggressive prosocial activities (e.g., learning in school) while making success at such activities possible (e.g., reducing class sizes).
  5. Increase the quality of prenatal and postnatal care, to decrease the proportion of the population suffering from developmental difficulties that interfere with normal learning and socialization processes (Anderson in press).
  6. Increase the quality of parenting, by providing instruction, social support, and economic support.


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Craig A. Anderson


views updated May 17 2018


i. Psychological AspectsLeonard Berkowitz


ii. International AspectsFrederick L. Schuman



The study of aggression—here regarded as any behavior whose goal is the injury of some person or thing (cf. Dollard et al. 1939)—has long been governed by philosophical preconceptions and clouded by hopes and fears. Writers have accounted for aggressive behavior in strikingly different ways: as the manifestation of an innate destructive drive, as an inborn reaction to frustrations, or as a learned way of responding to particular situations. Many of these interpretations have clearly been influenced more by metatheoretical beliefs regarding the nature of man or religiophilosophical hopes as to what human beings should be like than by carefully controlled and precise observations. Freud, as an example, at first had maintained that aggression was a “primordial reaction” to the blocking of pleasure-seeking or pain-avoiding strivings. However, partly because of his pessimism growing out of World War i, he revised his formulation and postulated the existence of an instinctive force of destruction and death (1920). Other psychologists have advanced entirely different conceptions. Some were predisposed to deny or minimize the role of innate factors in human behavior, while for others the notion of inherent aggressiveness was incompatible with their view of man as being basically good. Whatever the exact nature of their analysis, all too often their general theoretical or philosophical assumptions resulted in a relatively extreme stand in which some factors were given very heavy emphasis and others were played down or denied altogether.

Instinct conceptions

The Freudian “death instinct.”

In Freud’s post-1920 discussion of aggressive behavior, the dominant tendency in all organic life was held to be the effort to reduce nervous excitation to the lowest possible level (1920). Just as all pleasure-seeking was supposedly oriented toward tension reduction, all organic life presumably sought death, for to die was to be free from stimulation. (Freud also proposed that death was often sought violently rather than quietly and peacefully.) But this initial striving for active self-annihilation did not find fulfillment, Freud maintained, because the death instinct, Thanatos, was opposed by the life instinct, Eros, which diverted the destructive drive from the self to others. Thus, in attacking other people the person found a release for pressures that otherwise would impel him to seek his own death.

Empirical evidence provides little support for Freud’s analysis of aggressive behavior (cf. Berkowitz 1962). To cite just one difficulty, research clearly indicates that organisms do not seek the complete elimination of excitation. There are many situations in which human beings, as well as lower animals, work for an increase in stimulation (White 1959). Death is not necessarily the inherent aim of all organic life.

Other instinct doctrines

A number of biologists as well as orthodox psychoanalysts have accounted for aggression solely in terms of some inner force. The ethologist Konrad Lorenz (1952) has suggested, for example, that excitation is built up in each instinctive center within the central nervous system and is then dissipated when the instinctive act is performed. If an animal did not engage in aggressive behavior, “action-specific energy” would supposedly accumulate within the instinctive center controlling aggression. When enough energy is built up the action pattern presumably would go off by itself, that is, there would be “vacuum activity.” In contrast to this notion of spontaneous aggression, others (for example, Scott 1958) have maintained that there is no evidence of a spontaneous stimulation for fighting arising within the body. Actual fighting, which usually involves males belonging to the same species, is relatively rare in nature; in most cases the opponents display threat ceremonies instead of coming to blows.

Exteroceptive cues. In contrast to the model based on notions of energy accumulation, many students prefer to analyze instincts as species-specific behavior patterns governed by exteroceptive stimuli, which activate and terminate the actions. External stimuli are thus considered to be important contributors to aggressive behavior. Fighting behavior in many species varies with the nature of the antagonist—whether the animal’s opponent is from its own or some other species, and if the latter, whether it is a predator or some prey (EiblEibesfeldt 1963). More than determining merely the form of the response, external cues often appear to be necessary for eliciting any kind of hostile actions. Tinbergen (1951) observed that the male stickleback fish attacked a dummy with a red spot on its belly but ignored a detailed replica of the stickleback that did not have this characteristic of the breeding male or that had the red spot on its back.

Fighting arising from competition for dominance, food, sexual partners, or territory clearly attests to the role of external stimulation in animal aggression. The aggressive activity in these cases is the product of some perceived obstacle to the attainment of a desirable goal state. Even apparently noncompetitive fighting may be explained in these terms; the combat may have been instigated in order to achieve such things as dominance or undisturbed possession of living space (cf. Berkowitz 1962, p. 17).

Internal conditions. The efficacy of external stimuli in evoking aggressive behavior, however, is probably contingent upon the presence of some suitable internal condition. In the case of the stickleback fish the necessary internal prerequisite seems to be the production of the hormones involved in reproduction. Given the required internal state, a particular stimulus evokes the aggressive response. As yet another illustration of this principle, von Holst and von Saint Paul (1962) have shown that electrical stimulation of a certain region of the fowl brain results in recognizable aggressive actions only in the presence of relevant cues, “an enemy real or artificial.” Applying this formulation to competitive fighting, we can say that the rivalry produces an emotional state creating a readiness to engage in aggressive activity and that the competitor then provides the cue that releases (or evokes) the aggression.

The frustration–aggression hypothesis

The principle just advanced is a version of the “frustration-aggression hypothesis,” which has long been used to account for aggressive behavior. Independently espoused by such writers as Freud (prior to World War I) and McDougall (1908), the hypothesis was spelled out most clearly by Dollard, Doob, Miller, Mowrer, and Sears in a now-classic monograph published in 1939. Briefly, these psychologists maintained that a frustration—“an interference with the occurrence of an instigated goal-response at its proper time in the behavior sequence”—arouses an instigation to aggression (Dollard et al. 1939, p. 7). Since this formulation has been criticized frequently, some additional points should be made clarifying and defending it. First, Dollard and his colleagues did not claim that frustration had no consequences other than aggression. A thwarting will produce instigations to many different kinds of responses. Some of these other response tendencies may be stronger than the instigation to aggression, and the aggression is not revealed openly (Miller 1941). Moreover, although the hypothesis did say that all aggressive actions presuppose the existence of frustration, a person does not have to be frustrated in order to engage in aggressive actions (Bandura & Walters 1963). A contemporary revision of the frustration-aggression hypothesis must be less sweeping and all-explanatory than the original version.

This is not to say, however, that the hypothesis must be discarded altogether, as a number of writers have insisted (e.g., Buss 1961). While we cannot deal here with all of the criticisms (cf. Berkowitz 1962 for a more complete discussion), several of the arguments against the hypothesis can be answered.

Do only some frustrations produce aggression?

To begin, several psychologists have contended that only certain kinds of frustrations give rise to aggressive responses. Threats or attacks upon the self produce aggressive tendencies, they say, but mere deprivations supposedly lead to other consequences. In a similar vein, other critics have suggested that arbitrary or unexpected thwartings lead to aggression, while less arbitrary or expected frustrations presumably do not.

Two comments can be offered in rebuttal. Dollard et al. (1939) proposed that the strength of the instigation to aggression resulting from a frustration is in direct proportion to the strength of the thwarted drive. Since the desire for self-enhancement is typically fairly strong in our society, we would expect attacks upon the self to lead to stronger aggressive reactions than, say, interference with the performance of some unimportant task. Attacks upon the self then may lead to overt aggression, while the hostile responses produced by the interruption of a task that is not relevant to the self may be too weak to be apparent. But the frustration need not even be a direct attack on the self in order to produce aggression. Buss (1963) has demonstrated that college students who were prevented by a peer from attaining a desirable goal (such as a money prize) tended to display more intense open aggression toward the peer than did a nonfrustrated control group. The thwarting was not an arbitrary one, and the allowable aggression was not instrumental to the attainment of other ends, but there was a definite aggressive reaction, if only a weak one.

The second comment deals with the matter of deprivations and arbitrary frustrations. According to the definition employed by Dollard and his colleagues, a frustration is the blocking of some on-going, goal-directed activity. A person thoroughly engrossed in his work is not frustrated just because he has been without food for a number of hours. He may be deprived of food, but there are no ongoing eating response sequences, either in his thoughts or his overt activity, that are prevented from reaching completion. His failure to eat at his regular mealtime will therefore not produce an aggressive reaction. But what if this person had been prepared to eat at a certain time and had been thinking of the food he was soon going to enjoy? Suppose his employer unexpectedly gives him a sudden job that keeps him working late at night and causes him to miss his meal. We would now expect him to become angry. Whereas some psychologists would say he has now experienced an arbitrary or unexpected frustration, in contrast to an expected frustration, the present writer maintains that only now is he frustrated, whereas formerly, before he had anticipated eating, he was not. Only now is an ongoing response sequence prevented from reaching completion at its anticipated time (cf. Berkowitz 1962, pp. 36–42).

The innate nature of the aggressive reaction

American psychologists are characteristically reluctant to refer to instinctive or innate mechanisms in accounting for human behavior. Some of the objections to the frustration–aggression hypothesis seem to be dictated by this prejudice against the notion of innate reaction patterns.

Animals and humans can be trained to respond nonaggressively to situations that ordinarily produce hostile responses. For that matter, they can also learn to act aggressively in situations where formerly they had displayed little violence. In an experiment with school children, for example, Davitz (1952) rewarded one group of youngsters for acting aggressively and competitively, while another group was rewarded for cooperative and constructive behavior. After several training sessions all of the children were frustrated when a movie they were seeing stopped and, at the same time, their candy was taken away. Observations showed that the aggressively trained group exhibited more aggression in a free-play period immediately afterwards and that the constructively trained youngsters reacted more constructively to the thwarting. Scott (1958), after reviewing several of his animal experiments that had obtained essentially similar results, concluded that aggression was the product of previous learning. Taking much the same position, others (Bandura & Walters 1963) have argued that frustration produces a heightened motivational state that enhances the strength of whatever responses the individual has learned to make in the given situation; these may or may not be aggressive in nature.

Yet the experiments just mentioned do not really invalidate the frustration-aggression hypothesis. They demonstrate that previous experience can enhance or reduce the likelihood of aggressive behavior, but they do not prove that aggression will not occur under suitable conditions in the absence of any aggression training. Indeed, several experiments indicate that animals reared in isolation, and who had not previously learned to be aggressive, can react aggressively to arousing stimuli (Eibl-Eibesfeldt 1963, p. 11). In another demonstration that prior learning is not necessary for aggressive reactions, Seay and Harlow at the University of Wisconsin Primate Laboratory thwarted some infant monkeys by separating them from their mothers (1963). Six of the eight young animals subsequently displayed some aggression against a peer-playmate—but primarily when the previously frustrated infants were in their mothers’ presence. Two aspects of this finding are noteworthy. First, and most important, monkeys of the species used (rhesus) rarely show any aggression at all during the first year of life, and these particular infants had never before been observed to act aggressively. It is very unlikely, then, that they had learned aggressive actions earlier. Second, and we shall return to this point later, the aggressive response to a frustration is clearly revealed only under certain conditions.

Inflicting injury as a goal response

Another criticism of the frustration-aggression hypothesis as advanced by Dollard and others stems from a particular philosophy of science embraced by some psychologists. In saying that aggression was a behavioral sequence whose goal was the injury of the person to whom the activity was directed, the authors of the 1939 monograph implied that this behavior was purposive or intentional. Some writers, taking the position of Watsonian behaviorists, object to the inclusion of intentionality in the definition of aggression. Intentionality usually has to be inferred, and these critics prefer to confine themselves to a strict operationism having little room for inferences. While we cannot here debate the merits and demerits of this approach, there is reason to believe that aggressive frustration reactions are frequently purposive in nature. Hokanson and his students have shown that provoked subjects who are permitted to aggress against their tormentor often display a drop in systolic blood pressure that brings their pressure level close to that exhibited by a nonaroused control group. Systolic pressure does not decline as much, however, when the angered people can carry out some activity, but do not believe they have inflicted injury on their frustrater (even though the activity is physically comparable to the aggressive response), or when the aggression is directed against someone other than the person who had provoked them (cf. Hokanson et al. 1963). If the decrease in systolic blood pressure is a sign of physiological relaxation brought about by the performance of a goal response, engaging in mere activity or aggressing against just anyone does not seem to be sufficient to produce this tension reduction; the frustrated person (who wants, and is prepared, to attack his frustrater) may be primarily concerned with injuring the person who had provoked him.

A revised frustration–aggression hypothesis

Elsewhere (Berkowitz 1962) I have suggested that the original version of the frustration-aggression hypothesis should be modified in three ways. First, I would contend that a frustration—preventing the occurrence of some goal response at its proper time in an ongoing response sequence— arouses, among other things, an emotional state, anger, that creates a readiness for aggressive acts. (The arousal state produced by a thwarting also increases the strength of the ongoing responses, whether these are aggressive or not.)

Second, it is important to make explicit what was only implicit in the formulation advanced by Dollard and his coworkers. Aggressive responses do not occur, even given this readiness, in the absence of suitable cues—stimuli associated with the present or previous anger instigators. These cues, in other words, evoke aggressive responses from a person who is “primed” to make them. The strength of the aggressive response resulting from a frustration presumably is a function of the intensity of the aroused anger and the degree of association between the available stimuli and past and present anger instigators.

By suggesting that cues are necessary to elicit aggressive actions, we can explain two propositions advanced by Dollard and his coworkers: In the absence of inhibitions, the strongest hostile responses supposedly are directed toward the perceived source of the frustration; and progressively weaker aggressive responses theoretically are evoked by objects having less and less similarity to the frustrater. In both cases, the more direct the association with the anger instigator the stronger is the aggressive reaction that is elicited.

A third necessary revision of the frustration-aggression hypothesis restricts the extent to which thwartings are employed as an explanation of aggression. Instead of maintaining that all aggression “presupposes the existence of frustration,” we now recognize that (a) suitable cues may lead to aggressive behavior by arousing previously acquired aggressiveness habits and (b) such habits may be formed through learning—for example, by observing the behavior of some adult model—without involving a thwarting (Bandura & Walters 1963). To repeat, the revised hypothesis now would claim only that frustrations create a readiness for aggressive behavior.

Hostility displacement

The revised formula discussed above has some important implications for such phenomena as displacement and “scapegoating.” In the scapegoat theory of prejudice the victim is said to be attacked primarily because he is a visible and safe target for pent-up hostility within the prejudiced individual. The aggressive “drive” supposedly “pushes” aggressive acts onto safe, available targets. Contrary to such a view, the present position contends that a target with appropriate stimulus qualities “pulls” (evokes) aggressive responses from a person who is ready to engage in such actions either because he is angry or because particular stimuli have acquired cue value for aggressive responses from him.

Several experiments by the writer and his students offer support for this analysis of hostility displacement. In one study (Berkowitz & Green 1962) it was shown that subjects who were deliberately provoked by the experimenter subsequently exhibited greater hostility toward a person who had angered them some time earlier than toward someone else who had not provoked them. By having angered the subjects previously, the former person had acquired the cue value that now enabled him to evoke hostile responses from them when they were later thwarted by the frustrater. The writer suggests that those minority groups that frequently are the victims of displaced hostility, such as Negroes and Jews, are capable of eliciting aggressive responses from thwarted people because these groups are strongly disliked, that is, they had previously aroused anger. The dislike could arise from learning that the groups have unpleasant qualities as well as from prior frustrating experiences with them.

According to this reasoning, most explanations of social prejudice are too one-sided. Typically they either explain why some people are ready to act aggressively, or they provide reasons why certain minority groups are disliked. The present formulation attempts to integrate the two sets of explanations: we have to know both (a) why some people are “primed” to act aggressively and (b) what stimulus qualities are possessed by certain groups which enable them to evoke hostile responses from the people having a readiness to behave aggressively.

Comprehensive analyses of scapegoating must deal with those people who characteristically display relatively strong hostility toward minority groups. Recent research (Berkowitz 1959) indicates that highly ethnocentric college students typically have a strong tendency to attack other people when frustrated by someone else. It is not altogether clear, however, whether this tendency is due to (a) previously acquired aggressiveness habits; (b) a proclivity to establish broad categories, especially when under stress, so that in essence the immediate frustrater is not sharply differentiated from the others; (c) intense emotional arousal; or (d) some combination of these factors.

Inhibiting aggressive reactions

When an angered person displaces hostility, he presumably does so because fear or anxiety inhibits direct aggression against the frustrater. The analysis presented here helps explain why the displaced aggression is frequently quite intense. Miller’s (1948) translation of the psychoanalytic formulation maintains, as I indicated earlier, that stimulus objects increasingly removed from the frustrater on some appropriate generalization dimension would evoke weaker and weaker aggressive responses from the angered person. Attacks upon some bystander should thus be relatively weak and never stronger than the aggression that would be directed against the anger source. At least two studies, however, have obtained a substantial departure from this prediction. In one experiment (Pepitone & Reichling 1955), angered men whose inhibitions were presumably lowered by placing them in the company of others they liked exhibited the expected aggression gradient: much stronger attacks upon their tormentor than upon other associated stimuli. However, a more strongly inhibited group of men did not show this difference; the aggression they directed against the associated stimuli was practically as intense as the aggression against the anger instigator. Essentially similar findings have been obtained in other studies. Where members of a less inhibited group generally directed the strongest aggression against the source of their anger, most of the men in a more inhibited condition actually were more hostile toward the associated stimuli than toward the anger source (Berkowitz et al. 1963).

This last finding can be explained readily by noting that the inhibition of an aggressive response is a frustration. The emotional reaction produced by the thwarting should increase the strength of the individual’s aggressive proclivities. Since there is a restraint against a direct attack on the frustrater, attacks evoked by other stimuli should be strengthened. (Dollard and his colleagues had made this prediction in their 1939 monograph.)

Expectations to aggress

Anger arousal does not in itself necessarily lead to an instigated aggressive response sequence. Stimuli associated with the anger instigator must also be present. These cues may be provided either by the external environment or the individual’s thought processes. If a person is thinking of injuring his tormentor, the aggression goal (his frustrater) is symbolically represented in his thoughts. This symbolic representation serves as a cue setting an aggressive sequence into operation, if only internally. Preventing him from attacking his frustrater would then be an additional thwarting. Suppose, on the other hand, that the angered person does not see his tormentor, or any associated stimuli, and, for that matter, does not even think of “getting even.” There would be no ongoing aggressive sequence, and an inability to attack the anger source would not be a frustration.

Berkowitz and Luehrig have obtained data consistent with this reasoning (Berkowitz 1964a), demonstrating that angered male college students who had expected to be able to attack their frustrater but were prevented from doing so subsequently exhibited a high level of aggression toward him at the end of the session. The aggression they displayed toward him was stronger than that shown by other provoked people who had been able to attack this person earlier with electric shock or who, although not having been given this earlier opportunity, had not previously expected to be able to attack him. It is not enough just to say that a “set” or expectation had been thwarted in the former group without explaining the meaning of “set.” “Set” may consist of an implicit but nevertheless ongoing chain of responses. In the present case the implicit response sequence was activated by the anticipation of the aggressive opportunity, and the inability to satisfy this expectation was thus frustrating.

Hostility catharsis

Since the time of Aristotle, social science folklore has contended that an individual can be “purged” of his emotions by displaying his feelings. Aggressive behavior should therefore weaken the instigation to further aggression (unless he is frustrated again) and should somehow make the person feel better. But although such a proposition is almost universally accepted, empirical evidence regarding this catharsis hypothesis is far from unequivocal. We cannot be sure that catharsis takes place as readily and frequently as many people seem to assume.

There are manifold problems confronting research in this area. One difficulty is that observers have often regarded the intensity of the overt aggression following an initial attack as being a good indicator of the strength of the remaining “aggressive drive.” They forget that inhibitions produced by guilt or anxiety arising from the initial aggression may weaken any subsequent expressions of hostility. But even in the absence of such inhibitions, diminutions in aggressive tendencies following an intervening experience are also not necessarily due to a cathartic drainage of aggressive “energy.” An angered person who then watches a movie or a football game may calm down and become friendlier to his frustrater, not because he has discharged his anger vicariously but because he has been so distracted by the movie or game that he does not think of the thwarting he has experienced and ceases to stir himself up. Since he does not stimulate himself, his anger dissipates. To mention one other problem, the catharsis hypothesis is frequently tested by comparing an angered group that is permitted to aggress against someone with a similarly provoked group not given this aggressive opportunity. However, as we have already seen, if measurements obtained later should suggest there is a greater level of residual hostility in the latter (nonaggressing) condition, this difference may not be due to a catharsis in the group permitted to aggress; the angered people in the nonaggressing condition may have been frustrated —assuming they had wanted to, and had been prepared to, attack the anger source—and, so, they became more strongly aroused.

Clearly, given such difficulties, we cannot definitely say now that the free expression of aggression will automatically reduce the likelihood of subsequent aggression. Indeed, several studies of children in situations similar to play therapy suggest that the expression of aggression under such permissive conditions frequently serves to increase the probability of later violence (cf. Berkowitz 1962). The permissive situation may weaken inhibitions, and the performance of aggressive actions can strengthen aggressiveness habits. Nor does the observation of other people engaging in violence generally reduce aggressive tendencies. (1) The person who watches others acting aggressively often learns to behave aggressively through modeling himself after these others. (2) The witnessed hostility may provide cues activating previously acquired aggressiveness habits. (3) The witnessed hostility may affect the observer’s judgment of the propriety of his own aggressive desires.

To demonstrate this last-mentioned possibility, in three separate experiments Berkowitz (1964b) and his students showed a filmed prize fight scene to deliberately angered college men. In some cases the aggression they watched was made to appear justified (in that a villain received his “comeuppance”), while for other men the witnessed aggression was made to appear less warranted. Since the justified fantasy aggression lowered inhibitions against aggression—as indicated by several measures—the catharsis hypothesis would predict that the angered men in this group would participate vicariously in the filmed violence and, thus, would purge themselves of their anger. But contrary to this expectation, the angered men in this justified fantasy-aggression condition later displayed stronger aggression against their frustrater than did the similarly provoked group shown the less justified aggression. If aggression was warranted on the screen, the former may have thought, it was all right to attack the villain in their own lives.

Performing an aggressive act may well be a goal response completing an ongoing aggressive response sequence, but satisfactory completion is apparently attained only to the extent that (a) the angered person himself (or perhaps someone the person associates with himself) does the attacking and (b) the frustrater (or perhaps someone associated with him) is injured. Further, we are not altogether certain as to what the effects of this completion would be. It may well produce a feeling of tension reduction, especially if the angered person had wanted to, and had been prepared to, aggress against the anger instigator but, for some reason, had not been able to do so right away. Whether the tension reduction signifies a decreased likelihood of subsequent aggression is not altogether clear, however. The aggressive act may lessen the thwarted person’s anger at the moment, and thus may lower the probability of aggression at this time. But this frustrater has also acquired cue value for aggressive responses. Much like a red flag waved in front of a bull, under appropriate conditions (such as another thwarting experience) this individual may again evoke aggressive responses from the aroused person, whether or not he was the cause of the thwarting.

The reasoning just advanced obviously differs sharply from the “drainage” conception of aggressive behavior. Contrary to the notion of a free-floating aggressive energy that may be released through many different activities (for example, attempting to master others), or in attacking a wide variety of objects, available evidence suggests that the catharsis hypothesis must be restricted in scope. Moreover, if the view given here is correct, it is not necessary to provide substitute activities in order to “drain” a supposed reservoir of pent-up emotion. Unless the thwarted person is kept aroused or is rearoused, his anger probably will dissipate with time, and the probability of aggression will decline. But even if he is angry or has developed aggressiveness habits, aggressive behavior presumably will not occur unless appropriate cues are present.

Leonard Berkowitz

[Directly related are the entries Conflict; War. Other relevant material may be found in Instinct; Psychoanalysis; Stress.]


Bandura, Albert; and Walters, R. H. 1963 Social Learning and Personality Development. New York: Holt.

Berkowitz, Leonard 1959 Anti-Semitism and the Displacement of Aggression. Journal of Abnormal and Social Psychology 59:182–187.

Berkowitz, Leonard 1962 Aggression: A Social Psychological Analysis. New York: McGraw-Hill.

Berkowitz, Leonard 1964a Aggressive Cues in Aggressive Behavior and Hostility Catharsis. Psychological Review 71:104–122.

Berkowitz, Leonard 1964b The Effects of Observing Violence. Scientific American 210, February:35–41.

Berkowitz, Leonard; Corwin, R.; and Heironimus, M. 1963 Film Violence and Subsequent Aggressive Tendencies. Public Opinion Quarterly 27:217–229.

Berkowitz, Leonard; and Green, J. A. 1962 The Stimulus Qualities of the Scapegoat. Journal of Abnormal and Social Psychology 64:293–301.

Buss, Arnold H. 1961 The Psychology of Aggression. New York: Wiley.

Buss, Arnold H. 1963 Physical Aggression in Relation to Different Frustrations. Journal of Abnormal and Social Psychology 67:1–7.

Davitz, Joel R. 1952 The Effects of Previous Training on Postfrustration Behavior. Journal of Abnormal and Social Psychology 47:309–315.

Dollard, John et al. 1939 Frustration and Aggression. Yale University Institute of Human Relations. New Haven: Yale Univ. Press.

Eibl-Eibesfeldt, IrenÄus 1963 Aggressive Behavior and Ritualized Fighting in Animals. Pages 8–17 in Jules H. Masserman (editor), Violence and War: With Clinical Studies. Academy of Psychoanalysis, Science and Psychoanalysis, Vol. 6. New York: Grune & Stratton.

Freud, Sigmund (1920) 1950 Beyond the Pleasure Principle. Authorized translation from the 2d ed., by C. J. M. Hubback. International Psycho-analytic Library, No. 4. New York: Liveright. → First published under the title Jenseits des Lustprinzips. A paperback edition, translated by James Strachey, was published in 1959 by Bantam Books.

Hokanson, J. E.; Burgess, M.; and Cohen, M. F. 1963 Effects of Displaced Aggression on Systolic Blood Pressure. Journal of Abnormal and Social Psychology 67:214–218.

Holst, Erich von; and Saint paul, Ursula von 1962 Electrically Controlled Behavior. Scientific American 206, March: 50–59.

Lorenz, Konrad 1952 King Solomon’s Ring: New Light on Animal Ways. New York: Crowell; London: Methuen.

Mcdougall, William (1908) 1936 An Introduction to Social Psychology. 23d ed., enl. London: Methuen. → A paperback edition was published in 1960 by Barnes and Noble.

Miller, Neal E. 1941 The Frustration-Aggression Hypothesis. Psychological Review 48:337–342.

Miller, Neal E. 1948 Theory and Experiment Relating Psychoanalytic Displacement to Stimulus-Response Generalization. Journal of Abnormal and Social Psychology 43:155–178.

Pepitone, Albert; and Reichling, George 1955 Group Cohesiveness and the Expression of Hostility. Human Relations 8:327–337.

Scott, John P. 1958 Aggression. Univ. of Chicago Press.

Seay, B. M.; and Harlow, Harry F. 1963 Personal communication.

Tinbergen, Nikolaas 1951 The Study of Instinct. Oxford: Clarendon.

White, Robert W. 1959 Motivation Reconsidered: The Concept of Competence. Psychological Review 66:297–333.


Power holders and decision makers in the parochial sovereignties into which mankind has been habitually divided have repeatedly resorted to armed violence against neighboring communities in pursuit of political objectives. Every such resort to force has invariably been regarded as aggression (hence as unjustified, illegal, and immoral) by its victims and, also invariably, been deemed moral, legal, and justified by the alleged “aggressors” on the grounds of “self-defense,” “preservation of the balance of power,” “national honor,” or some other plausible formula for rationalizing recourse to war.

Aggression as a concept or abstraction poses, therefore, a semantic and psychological problem rather than a problem admitting of solution by reference to traditional criteria of international law, diplomatic practice, military science, or international organization. In our time, aggression is a term of disapproval, usually limited to acts of military violence by “enemy” states whose purposes must be resisted. It is a prime article of faith, in the cult of nationalism, that aggression is always a crime committed by enemy governments and never a sin of one’s own nation-state. The obvious falsity of this dichotomy has had little or no effect on the behavior of those committed to its fallacies.

The problem is not so simple, however, as these introductory comments suggest. Whether, the propensity of human beings to resort to violence against other human beings is attributable to “instinct” or to “culture” has long been debated inconclusively. Some hold, with Sigmund Freud, that the human psyche is afflicted with a “death instinct,” which avoids suicide only by a triumph of Eros over Thanatos, or, more commonly, by deflection of aggression against the self to aggression against others. Others, along with Bronislaw Malinowski, hold that aggression is not innate but is a product of the frustration of other human aspirations.

The issue in international law

In the realm of interstate relations many people, and policy makers, confronted with the recurring tragedies of worldwide violence in the twentieth century, have earnestly striven to outlaw war and to forbid aggression by international agreement. All such efforts have thus far failed.

The “outlawry of war” was anticipated in many late medieval and early modern treaties whereby sovereignties solemnly pledged themselves to perpetual peace. Since such pledges had no discernible effect on the subsequent decisions of statesmen, the formula was abandoned in the nineteenth century. It was revived in the twentieth by the shock of World War i. The League to Enforce Peace, 1915-1919, championed American membership in a league of nations in which “aggression” was to be met with such overwhelming economic and military force that it would not be attempted.

The League of Nations Covenant of 1919 forbade recourse to war, with qualifications. The Kellogg-Briand Pact of 1928, which pledged its signatories to renounce war as an instrument of national policy, save in “self-defense,” was largely vitiated by the numerous national interpretations and reservations. Other bilateral and multilateral treaties of the 1930s reiterated the same goal. The Charter of the United Nations bound its members “to ensure, by the acceptance of principles and the institution of methods, that armed force shall not be used save in the common interest” and, further, “to maintain international peace and security, and to that end to take effective collective measures … for the suppression of acts of aggression or other breaches of the peace” (art. 1).

The assumption of the framers of the charter at San Francisco in the spring of 1945 was that a concert of powers, cooperating for common purposes, would guarantee peace and halt aggression by collective action, provided that the great powers with permanent seats on the Security Council would act unanimously on all measures of “enforcement” (cf. art. 27, the “veto” article of the UN Charter). The assumption proved false with the advent of the cold war in 1945/1946. Common action against aggression was henceforth impossible, with each contestant using real or alleged “aggression” by others as a weapon of propaganda, diplomacy, and strategy against the “enemy.”

Within the context of the logic of international law, aggression consists in resort to war or to measures of armed coercion short of formal war, undertaken in violation of treaty obligations not to resort to war or to other acts of force. In the years that followed the signing of the Kellogg-Briand Pact, national policy makers, with the support of all patriots, paid no attention to the legal duties they or their predecessors had assumed whenever prevailing concepts of “national interest” dictated an opposite course. Law is an effective guide to conduct only in organized communities whose members accept its purposes as paramount. The Western state system is not such a community.

The totalitarian states have provided numerous examples of violations of treaty obligations forbidding aggression—for example, the fascist conquest of Ethiopia in 1935-1936; the Nazi seizure of Austria and Czechoslovakia in 1938–1939; Axis intervention in Spain in 1936-1939; Hitler’s invasion of Poland in 1939; the Japanese assaults on China in 1931 and 1937 and on the United States in 1941; Stalin’s partition of Poland with Hitler in 1939; the Soviet attack on Finland in 1939-1940 and conquest of the Baltic states in 1940. However, the democracies have no better record. Witness, among recent instances, the abortive Anglo-French-Israeli attack on Egypt in 1956; India’s seizure by force of Hyderabad and Goa and attempted seizure by force in 1962 of territories in dispute between New Delhi and Peking; and the U.S. “spy flights” over the U.S.S.R. by U-2 planes (1955-1960), the Bay of Pigs invasion of Cuba in April 1961, and the “quarantine” of Cuba in October 1962. Other instances of resort to force come readily to mind, with each side accusing the other of “aggression”: the U.S. war on North Vietnam, launched February 7, 1965; the U.S. intervention in the Dominican Republic, April 28, 1965; the India-Pakistan war over Kashmir, September 1965.

The problem of definition

It is evident that decision makers in sovereign states do not abide by treaty obligations when “security” or “defense” or ambition dictates contrary conduct. This circumstance has led diplomats and legalists to cultivate the illusion that obedience to law could somehow be assured if only a more precise definition of aggression could be formulated and generally accepted. Laborious efforts at Geneva in the 1920s in the name of the League of Nations were devoid of operational results. Similar efforts by the United Nations since 1946 have been equally in vain. The most notable, albeit futile, attempt to define aggression was made by Maxim Litvinov, foreign minister of the U.S.S.R., at the London Economic Conference of 1933. On July 4 of that year he signed a “Convention for the Definition of Aggression” with envoys of Rumania, Yugoslavia, and Turkey (a few other states subsequently adhered). The signatories to this convention agreed to define the aggressor in an international conflict as that state which is the first to commit any of the following actions: (1) declaration of war upon another state; (2) invasion by its armed forces, with or without a declaration of war, of the territory of another state; (3) attack by its land, naval, or air forces, with or without a declaration of war, on the territory, vessels, or aircraft of another state; (4) naval blockade of coasts or ports of another state; (5) provision of support to armed bands formed on its territory which have invaded the territory of another state, or refusal, notwithstanding the request of the invaded state, to take on its own territory all the measures in its power to deprive those bands of all assistance or protection (art. 2). Furthermore, it was stipulated that no political, military, economic, or other considerations could serve as an excuse or justification for such acts of aggression (art. 3).

No better definition of aggression has been formulated since 1933. The futility of the enterprise is shown by the fact that Soviet policy makers in their “winter war” against Finland in 1939–1940 violated all the obligations they had so recently assumed. Other instances of violations of pledged words are innumerable in the diplomatic and military history of the twentieth century.

The dilemma

The premise of all efforts to outlaw war and to define and forbid aggression by bilateral or multilateral accords among sovereignties is that national policy makers will be deterred from misbehavior by their promises and by threats of action against them from the entire community of nations. In practice, the promises are frequently ignored, for reasons pointed out by Machiavelli more than four centuries ago. As for the efficacy of threats against aggressors in the name of collective security, the verdict of experience thus far is negative. National policy makers, dedicated to the pursuit of the national interest, whether this is defined in terms of power, pride, profit, or prestige, can always be relied upon, whatever their rationalizations, to ignore their commitments to refrain from aggression whenever they believe that resort to force will serve their purposes.

Aggression can probably never be prevented by legalistic formulae or by the artifacts of international organization and collective security, so long as the state system remains an arena of international anarchy among polities possessed of unlimited national sovereignty. Aggression will cease only when mankind reluctantly accepts the necessity of a drastic alteration of values and purposes in international relations and gives operational meaning to the ideal of world government. This goal is remote because of the universal disposition of Homo sapiens to cling to ancient ways in the face of new circumstances calling for new thought and threatening disaster if rethinking is resisted. In the absence of significant progress toward this objective, aggression in interstate relations will continue in the future, as in the past, with potentially catastrophic consequences—and all efforts to define, outlaw, and forbid recourse to force by one state against another must inevitably fail of their purpose.

Frederick L. Schuman

[See alsoCollective security; International law; War.]


Boggs, Marion William 1941 Attempts to Define and Limit Aggressive Armament in Diplomacy and Strategy. Columbia: Univ. of Missouri Press.

Langer, Robert; and Schuman, Frederick L. 1947 Seizure of Territory: The Stimson Doctrine and Related Principles in Legal Theory and Diplomatic Practice. Princeton Univ. Press.

Litvinov, Maxim 1939 Against Aggression. New York: International Publishers. → Speeches, together with texts of treaties and of the Covenant of the League of Nations.

Research in International Law, Harvard Law School 1939 Draft of Conventions Prepared for the Codification of International Law. Concord, N.H.: Rumford Press. → Also published as a supplement to Volume 33 of the American Journal of International Law, 1939.

Stone, Julius 1958 Aggression and World Order: A Critique of United Nations Theories of Aggression. Berkeley: Univ. of California Press.


views updated Jun 27 2018


Theologians and moralists have long attempted to restrict the use of force by states through elaborating the concept of just and unjust wars, condemning those deemed unjust. Legal efforts to outlaw recourse to war came much later, mostly dating from World War I. Until that time, international law placed certain limitations on and pre-requisites to warfare, but did not prohibit it altogether. War was still perceived as a legitimate means of achieving political objectives.

From World War I to Nuremberg

World War I ("the war to end all wars") left ten million deaths in its wake, eliminating an entire generation of young men in Europe. This catastrophe led countries to seek ways to ban war as an exercise of State sovereignty. U.S. Secretary of State Frank Kellogg, the French Minister of Foreign Affairs Aristide Briand and the German Minister of Foreign Affairs Gustav Stresemann spearheaded negotiations to conclude a treaty that would achieve this aim. On August 27, 1928, in Paris the Kellogg-Briand Pact was signed and opened for adherence by states. By virtue of Article I of this short text, the forty-five State parties "condemn recourse to war for the solution of international controversies, and renounce it, as an instrument of national policy;" in Article II they "agree that the settlement or solution of all disputes or conflicts of whatever nature or of whatever origin they may be . . . shall never be sought except by pacific means."

As a corollary to the Pact, a subsequent American Secretary of State, Henry Stimson, enunciated the doctrine of non-recognition of international territorial changes effectuated by force. This doctrine was a response to Japan's unilateral seizure of Manchuria in September 1931. The Stimson doctrine was subsequently incorporated in several international declarations, including a League of Nations resolution of March 11, 1932; the Inter-American Pact of Rio de Janeiro of October 10, 1933; and the Budapest Articles of Interpretation (September 10, 1934) of the Kellogg-Briand Pact.

Germany and Italy were among the state parties to the Pact, but this did not prevent the outbreak of World War II, in which Hitler was the principal, but not the only aggressor. The Soviet Union, for instance, joined Germany in attacking Poland in September 1939, pursuant to a secret treaty signed by foreign Ministers Ribbentrop and Molotov, in which they divided Poland between the two countries. In October 1939 the Soviet Union occupied and annexed the three Baltic States of Estonia, Latvia and Lithuania. In November 1939, it took 18,000 square miles of Finnish territory and forced 450,000 Finns to resettle elsewhere. For the latter aggression the Soviet Union was formally expelled from the League of Nations in December 1939.

Following German capitulation in May 1945, the Allies adopted the London Agreement of August 8, 1945, which contained the Charter of the Nuremberg Tribunal. Article 6(a) of this charter provided for prosecution for crimes against peace: "namely, planning, preparation, initiation or waging of a war of aggression, or a war in violation of international treaties, agreements or assurances, or participation in a Common Plan or Conspiracy for the accomplishment of any of the foregoing." Many Nazis leaders were indicted and convicted of this offence, seven of whom were sentenced to death. Despite the adherence of Germany to the Kellogg-Briand Pact, controversy emerged over whether or not the inclusion of "crimes against peace" amounted to the enunciation of new law and made the prosecutions contrary to norms of justice prohibiting punishment for offenses ex post facto. It is clear that the Kellogg-Briand Pact prohibited recourse to war, but it did not include any reference to personal responsibility or international crimes, so the issue remains subject to debate.

Whatever the legal position before the London Charter, the illegality of aggression was settled in its aftermath. By virtue of General Assembly Resolution 95(1) of December 11, 1946, the Nuremberg judgment, including the condemnation of aggression, was recognized as binding international law. At the same time, the International Law Commission was entrusted with drafting what became known as the "Nuremberg Principles," which were adopted in July 1950, and included a definition of the crime against peace.

In General Assembly Resolution 177(II) of November 21, 1947, the International Law Commission was further mandated to prepare a code on offences against the peace and security of mankind. After nearly forty years of effort, the International Law Commission adopted in 1996 a "Draft Code on Crimes Against the Peace and Security of Mankind" (not yet approved by the UN General Assembly). Article 16 of the draft code contains the following statutory definition: "An individual who, as leader or organizer, actively participates in or orders the planning, preparation, initiation or waging of aggression committed by a State shall be responsible for a crime of aggression."

Defining Aggression

General Assembly Resolution 3314 (XXIX) of December 14, 1974, constitutes the most detailed statement of the United Nations on aggression. The resolution defines aggression in its first articles. Article 1 provides:

Aggression is the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations.

Article 2 stipulates:

The first use of armed force by a State in contravention of the Charter shall constitute prima facie evidence of an act of aggression although the Security Council may, in conformity with the Charter, conclude that a determination that an act of aggression has been committed would not be justified in the light of other relevant circumstances, including the fact that the acts concerned or their consequences are not of sufficient gravity.

Article 3 lists a series of acts which, regardless of a declaration of war, would constitute aggression, including the invasion or attack by the armed forces of a state of the territory of another state, bombardment by the armed forces of a state against the territory of another state, the blockade of the ports or coasts of a state, and the sending of armed bands, groups, irregulars, or mercenaries, which carry out acts of armed force against another state.

Article 5 warns that "no consideration of whatever nature, whether political, economic, military or otherwise may serve as a justification for aggression. A war of aggression is a crime against international peace. Aggression gives rise to international responsibility. No territorial acquisition or special advantage resulting from aggression is or shall be recognized as lawful."

Article 7 explains, however, that "nothing in this declaration . . . could in any way prejudice the right to self-determination, freedom and independence, as derived from the Charter, of persons forcibly deprived of that right and referred to in the Declaration on Principles of International Law concerning Friendly Relations and Cooperation among states in accordance with the Charter of the United Nations, particularly peoples under colonial and racist regimes or other forms of alien domination, nor the right of these peoples to struggle to that end and to seek and receive support, in accordance with the principles of the Charter and in conformity with the above-mentioned Declaration."

The UN General Assembly has reaffirmed the consensus definition in several declarations, including the Declaration on International Détente (Res.32/155 (1977)) the Declaration of Societies for Life in Peace (Res. 33/73 (1978)), the Declaration on the Non-Use of Force (Res. 42/22 (1988).

UN Efforts to Combat Aggression

The United Nations was founded "to save succeeding generations from the scourge of war" (preamble), and Article 1, paragraph 1 of the Charter establishes its mandate "to maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression. . ." Article 2, paragraph 3 imposes an obligation to resolve international disputes peacefully: "All members shall settle their international disputes by peaceful means." Finally, Article 2, paragraph 4 specifically engages States to "refrain in their international relations from the threat or use of force."

The Charter prohibition of force has been repeated in countless resolutions of the Security Council and of the General Assembly. It is detailed most importantly in GA Resolution 2625 (XXV) of October 24, 1970, Resolution on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the Charter of the United Nations, which solemnly proclaims that

Every State has the duty to refrain in its international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the purposes of the United Nations. Such a threat or use of force constitutes a violation of international law and the Charter of the United Nations and shall never be employed as a means of settling international issues. A war of aggression constitutes a crime against the peace, for which there is responsibility under international law. In accordance with the purposes and principles of the United Nations, States have the duty to refrain from propaganda for wars of aggression.

The Security Council has, however, avoided labeling breaches of the peace as acts of aggression. Even in a case as clear as the 1990 aggression toward Kuwait by Iraq, the Security Council condemned it merely as an "invasion and illegal occupation" (Res. 674/1990), and decided that "the annexation of Kuwait by Iraq under any form and whatever pretext has no legal validity, and is considered null and void" (Res. 662 (1990)). However no reference was made to the application of Article 3(a) of the definition of aggression, or to the penal consequences pursuant to Article 5.

Other uses of force since World War II could be measured against the standards laid down by the UN Charter, the Nuremberg Principles and the Declaration on the Definition of Aggression. These incidents include Dutch "police actions" in Indonesia (1947–1950), the French Indochina wars (1952–1954), the French-Algerian conflict (1954–1963), the sinking of the Greenpeace vessel "Rainbow Warrior" in Auckland Harbour in New Zealand, the war over the Belgian Congo (1960–1962), the Indian-Pakistani war 1970–1971, the Warsaw Pact's invasion of Czechoslovakia in 1968, the Soviet Union's occupation of Afghanistan in 1980, the Iraq-Iran War (1980–1990), the Turkish invasion of Cyprus in 1974 and the Vietnam War.

Justifications for the Use of Force, Self-Defense

There are, of course, some justifications for the use of force which are legitimate according to international law. Article 51 of the UN Charter stipulates: "Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security."

The application of this provision is, however, strictly limited by the over-all obligation to negotiate set forth in Article 2, paragraph 3, and the prohibition of the threat of or the use of force in Article 2, paragraph 4 of the UN Charter. In his address to the General Assembly on September 23, 2003, Secretary General Kofi Annan stated: "Article 51 of the Charter prescribes that all states, if attacked, retain the inherent right of self-defence. . . until now it has been understood that when states go beyond that, and decide to use force to deal with broader threats to international peace and security, they need the unique legitimacy provided by the United Nations." The International Court of Justice has specified the situations in which Article 51 can be invoked, most recently in an advisory opinion of July 9, 2004. The consensus of international law experts is that preventive or pre-emptive war is not compatible with article 51 of the charter, which requires an existing "armed attack" and places overall responsibility on the Security Council.

Humanitarian intervention is another possible justification for the use of force, and it remains the responsibility of the Security Council to legitimize or not a given military intervention. For example, approval was given in Resolution 688 of April 5, 1991, with respect to the necessity to create safety zones for Kurds and other minorities in Iraq. Humanitarian intervention would also have been possible in order to stop the genocide in Cambodia (1975–1979) or in Rwanda (1994).

While humanitarian intervention may be an international duty in order to stop genocide and crimes against humanity, it must not become a cloak or an excuse for military interventions responding to other political agendas. For instance, Human Rights Watch recently conducted a study of the arguments advanced by the United States as justification for the war on Iraq begun in 2003, and concluded that the U.S. intervention did not satisfy the constitutive elements of a humanitarian intervention.

Individual Responsibility

Aggression is not only an internationally wrongful act giving rise to State responsibility and the obligation to make reparation; it is also an international crime giving rise to personal criminal liability. The Diplomatic Conference of Rome adopted on July 18, 1998 the Statute of the International Criminal Court, which defines the jurisdiction of the Court in its Article 5, including with respect to the crime of aggression. Paragraph 2 of Article 5, however, stipulates: "The Court shall exercise jurisdiction over the crime of aggression once a provision is adopted in accordance with Articles 121 and 123 defining the crime and setting out the conditions under which the Court shall exercise jurisdiction with respect to this crime." This delay in the exercise of the Court's competence with regard to aggression is primarily attributable to the opposition of the United States. However, since the United States has indicated that it will not ratify the treaty, the assembly of States parties to the Rome Statute is now free to adopt a definition consistent with the judgment of the Nuremberg trials.

None of the Special Tribunals created since have jurisdiction over the crime of aggression, neither the International Tribunal for the Former Yugoslavia, nor the International Tribunal for Rwanda, nor the Iraqi Special Tribunal. Precisely because no international tribunal has been given competence to try aggressors for the crime of aggression, a number of representatives of civil society have organized "People's Tribunals."

Notable among these are the Russell Tribunal on the Vietnam War, organized by British pacifist Bertrand Russell and French philosopher Jean Paul Sartre (held 1967 in Sweden and Denmark) and the Brussels Tribunal on the Iraq War organized by former Attorney General Ramsey Clark (April 2004). The latter was conducted with the participation of two ex-United Nations humanitarian coordinators for Iraq, Dennis Halliday and Hans von Sponeck. Both tribunals condemned the United States as an aggressor in Vietnam and as an aggressor in Iraq. There is also a "Permanent People's Tribunal" (Fondation Internationale Lelio Basso), which has held more than 30 sessions, one of them in Paris in 1984, devoted to the genocide against the Armenians, and one held in Rome in 2002 devoted to international law and the new wars of aggression.

A Human Right to Peace

The international prohibition of aggression may also be viewed as asserting a human right to peace. On November 12, 1984 the United Nations General Assembly adopted Resolution 39/11, annexing the Declaration on the Right of Peoples to Peace. This declaration reaffirms that "the principal aim of the United Nations is the maintenance of international peace and security" and the "aspirations of all peoples to eradicate war from the life of mankind and, above all, to avert a world-wide nuclear catastrophe." By virtue of operative paragraph 2, the declaration proclaims that "the preservation of the right of peoples to peace and the promotion of its implementation constitute a fundamental obligation of each State." In paragraph 3, the declaration "demands that the policies of States be directed towards the elimination of the threat of war, particularly nuclear war, the renunciation of the use of force in international relations and the settlement of international disputes by peaceful means."

This declaration has been reaffirmed in resolutions of the General Assembly and of the United Nations Commission on Human Rights. In its Resolution 2002/71 of April 25, 2002, the Commission linked the right to peace with the right to development and affirmed that "all States should promote the establishment, maintenance and strengthening of international peace and security and, to that end, should do their utmost to achieve general and complete disarmament under effective international control, as well as to ensure that the resources released by effective disarmament measures are used for comprehensive development, in particular that of the developing countries." The resolution urged "the international community to devote part of the resources made available by the implementation of disarmament and arms limitation agreements to economic and social development, with a view to reducing the ever-widening gap between developed and developing countries."

In a world of weapons of mass destruction, it is imperative to strengthen the early warning and peaceful settlement mechanisms of the United Nations. In view of the human consequences of war, aggression must be prevented through international solidarity. The idea that has become the norm is that no country can take the law in its own hands. Force can only be used as a last resort and only with approval of the UN Security Council.

SEE ALSO Humanitarian Law; International Criminal Court; Peacekeeping; United Nations Security Council; War; War Crimes


Bassiouni, M. Cherif (1998). The Statute of the International Criminal Court: A Documentary History. New York: Transnational Publishers.

Cassin V. et al. (1975). "The Definition of Aggression" Harvard International Law Journal 16:598–613.

Dinstein, Yoram. War, Aggression, and Self-Defence, 2nd edition. Cambridge, U.K.: Grotius.

Fastenrath, Ulrich (2002). "Definition of Aggression." In A Concise Encyclopedia of the United Nations, ed. H. Volger. Hague: Kluwer Law International.

Ferencz, Benjamin (1975). Defining International Aggression, the Search for World Peace: A Documentary Analysis, 2 volumes. Dobbs Ferry, N.Y.: Oceana.

Roth, Kenneth (2004). "War in Iraq: Not a Humanitarian Intervention." Available from

Alfred de Zayas


views updated May 18 2018

aggression has been defined as a behaviour characterized by the intention of inflicting unpleasant stimulation on another individual — but this underestimates its subtlety and omits some important features. It is well known that aggression is not a simple, single category of behaviour. Several classifications of aggression have been proposed, some more elaborate than others. Aggression, unlike some other behaviours, has no biological function or purpose in isolation. Aggressive interactions occur mostly as part of some other pattern of behaviour; for example, as a strategy to achieve sexual goals or access to preferred foods. More generally they form part of the process whereby individuals define their position in the social groups to which they belong, and hence ensure access to restricted resources without the need for constant conflict — a form of social control. However, this does not rule out the possibility that the performance of aggressive acts can itself be rewarding.

Distinctions have been made between different types of aggression, largely on the basis of the context in which it occurs or the stimuli that provoke it: (i) inter-male, or inter-female (territorial, social conflict, etc.); (ii) maternal; (iii) self defence; and (iv) infanticide. Aggression towards members of the same species has been divided more simply into ‘offence’ and ‘defence’. Predation, the hunting of other species, is sometimes included in discussions of aggressive behaviour, but is more properly classed as feeding behaviour.

Human aggression has been separated into ‘emotional’ aggression, carried out by people with the main intention of harming someone, and ‘instrumental’ aggression, with some other objective, such as to obtain something rewarding, rather than specifically to injure a victim. In general, both the form of the aggressive act and the context in which it occurs have to be taken into account.

Social factors

Most species, including human beings, live in social groups whose structure affects access by individuals to items in short supply — such as food, mates, or shelter. Direct aggressive confrontation may be used to determine which individual has priority, but it is more usual that animals come to know, through a process of social learning, who is likely to win in such an encounter. This determines their strategy, and also gives the group its dominance structure. Animals, or people, low in the hierarchy may not challenge those higher in the scale, presumably because of the cost in terms of potential injury. This mechanism of social control, based on previous aggressive interactions, functions to reduce aggression; but it does have potent effects on individuals. If it is to be effective, social control by hierarchy requires extremely sophisticated neural processing; indeed, there are those who claim that the primary function of the human brain is to facilitate social interaction.

Gender influences

There are marked individual and gender-related differences in aggression. In most mammalian species aggression is more common between males than between females. Exposure of the brain to testosterone in the womb may alter infant behaviour: young males show more aggressive-like play than females. Testosterone may also sensitize the individual to the later effects of the same hormones: for example, increasing the likelihood of adult aggressive behaviour, particularly in the context of competition for desirable, but limited, resources. However, giving excess testosterone to men has had rather inconspicuous effects on their aggressive behaviour or tendencies (including thoughts), though levels of testosterone in the saliva have been shown to correlate positively with violent crimes in male prison inmates. But social status also alters testosterone, so the relation between individual differences in aggressivity and testosterone may be indirect. A variety of studies, in both human and non-human primates, has shown that social ‘stress’ (that is, demands made by the social or working environment) lowers testosterone and that ‘dominant’ males have higher levels. However, injecting ‘subordinate’ monkeys with testosterone does not improve their position in the hierarchy, or make them more aggressive.

Aggression is not a male prerogative. It also occurs in females, particularly when they need to defend their young. For example, lactating rats are highly aggressive to intruding males (rather than females). In this context, different hormones may play a role. This aggressive reaction seems to depend upon suckling, and has the obvious biological function of protecting the young. Testosterone given to lactating females actually reduces their aggressive reaction to males.

Are specific parts of the brain involved in aggression?

Since much of aggression in the biological world is part of another behaviour, it is difficult to separate those areas of the brain responsible for the underlying behaviour (getting food, winning mates, etc.) from those associated with the particular behavioural strategy of aggression to achieve these ends. It has been known for many years that damage to a part of the brain called the amygdala results in ‘tameness’ and reduced aggression. The amygdala is part of the limbic system, a set of brain structures particularly concerned with survival, adaptation, and the defence of the body against the metabolic or social demands that constitute stress. The amygdala is closely involved in the ability of the brain to classify stimuli in a motivationally and emotionally meaningful way. Its role is not, therefore, restricted to aggression, but this along with many other behaviours is dependent on proper functioning of this part of the brain. Human cases are known in which disturbances of the amygdala have led to inappropriate or excessive aggression.

Another area of the brain implicated in aggression is the hypothalamus. Lesions or stimulation in several areas of the hypothalamus have altered aggressive interactions. The hypothalamus is implicated in other behaviours. For example, part of it has well-established roles in sexual and maternal behaviour, and it is prominently involved in the regulation of feeding and drinking. Bearing in mind the relation between aggression and other categories of adaptive behaviour, it is clear that there is still uncertainty about the exact role of the hypothalamus in aggression, and whether this can be truly separated from its other adaptive and homeostatic functions. Nevertheless, there are well-documented cases describing humans with tumours in the particular parts of the hypothalamus who became highly aggressive, responding with aggression to stimuli they would have previously considered only annoying. ‘Sedative’ surgical interventions, involving the hypothalamus, have been used in the treatment of aggressive patients.

We have seen that aggression forms an important part of social regulation and social interaction. This is known to involve the cortex of the frontal lobes of the brain. The frontal cortex is also intimately connected with both the amygdala and the hypothalamus and is therefore in a position to influence these other brain centres that control aggression. This behaviour can occur as a feature of frontal lobe damage in man. Patients with damage in one region of the frontal cortex react impulsively, without planning or taking into account the consequences of their behaviour; they are irritable and have short tempers, responding to minor provocation. But the frontal cortex is a complex area of the brain, and it is still not very clear whether particular parts may have distinct roles in aggression.

Are there specific aggression-related chemicals in the brain?

The brain is a chemical machine, and the recognition that different parts can be defined by the chemical transmitters that they use offers a different perspective. In humans, changes in the level and metabolism of serotonin have been correlated with affective behaviour in general and more specifically with aggressive behaviour. Serotonin has become the major focus of biological studies of suicidal behaviour (defined as ‘self-aggression’) and impulsive aggressive behaviour in humans. An association has been reported between low serotonin concentration in the brain and impulsive, destructive behaviours, particularly when aggression and violence are involved. Studies in animals show that a wide range of aggressive behaviours are sensitive to manipulations of the serotonergic system. Depletion of brain serotonin increases aggression. Conversely, serotonergic-enhancing drugs, such as the specific serotonin-uptake inhibitors (SSRIs), reduce aggression. A class of drugs acting on serotonin are known as ‘serenics’; these reduce aggression.

But serotonin is not the only neurochemical implicated in aggression. Animal studies suggest that increasing brain dopamine activity creates a state in which they are more prepared to respond aggressively to stimuli in the environment. Antagonists of dopamine receptors are the most frequently used therapeutic agents in the management of violent patients. However, dopamine has important roles in generalized behavioural categories such as reward or punishment; this may be the real reason why it contributes to the display of aggression.

Hyperactivity of noradrenaline in the brain has been found to correlate with aggressive behaviour in humans, and noradrenergic receptor blockade is clinically useful in its treatment. This is supported by the effects on aggressive behaviours in isolated mice of drugs that modify noradrenaline activity in the brain.

Many peptides are found in the brain, particularly in the limbic system, that act as neurotransmitters. One of these, corticotrophin releasing factor, is present throughout the limbic system. It has an important role in organizing the co-ordinated response to stress; this includes behaviour, hormones, and the emergency systems regulating the cardiovascular and other autonomic responses. It may also increase aggression. Vasopressin (first known as a pituitary hormone) is another peptide found in the limbic system, and microinjections of this into the hypothalamus and amygdala increased offensive aggression in rodents. Although alterations in several peptides, as well as other substances, are known to change aggression, no single one so far has been specifically associated with this behaviour. Clearly, given the current preoccupation with understanding and controlling aggression in man, the existence of such compounds, should they be proved, would be most important.

The complexity of aggression — the behaviour pattern, the contexts in which it occurs, and the uses to which it is put — means that there can never be a single, definable system underlying it. Nevertheless, attempts should continue to define aggression more precisely, since this offers not only greater understanding of the relation between this behaviour and others but also direct help to those who try to control undesirable aggression in either animals or humans.

J. Herbert


Albert, D. J.,, Walsh, M. L.,, and and Jonik, R. H. (1993). Aggression in humans: what is its biological foundation? Neuroscience and Biobehavioural Reviews, 17, 405–25.
Archer, J. (1988). Behavioural biology of aggression. Cambridge University Press.
Valzellli, L. (1981). Psychobiology of aggression and violence. Raven Press Books, New York.

See also hormones; peptides; serotonin; violence.


views updated May 11 2018


The word aggression comes from the Latin roots ag (before) and gred (to walk or step). Hence to aggress is to step before or in front of someone, to initiate something, commonly an attack. Aggression—whether by a state or an individual—refers to an unprovoked, offensive action against another. It is useful to contrast aggression with violence, which derives from the Latin root vio, which refers to force. Dictionary definitions include "rough, unjust, unwarranted and injurious physical force or treatment," as well as "immoderate vehemence, typically causing injury, pain or gross distortion." It is possible to talk about a violent storm, or an earthquake of exceptional violence, but the term is most often applied to human actions, in which case it generally implies that pain or injury is intentionally inflicted on someone or something.

By contrast aggression is not necessarily hurtful: A person may promote a viewpoint aggressively, for example, which implies initiative, forcefulness and assertiveness, but without injury. It is admirable to conduct an aggressive campaign against cancer, poverty, or illiteracy. One may even seek to aggressively oppose violence. Nonetheless aggression as such is not highly regarded; it, like its frequent concomitant, violence, is typically considered undesirable, at least from the perspective of most ethicists.

Aggression Among Animals

Aggression is widespread among animals, especially those living in social groups. Although it sometimes takes the form of clear, outright violence, aggression is more often subtle, involving intimidation and the displacement of one individual by another, typically in the context of established dominance hierarchies. Early scientific studies of animal behavior emphasized that animal aggression very rarely results in serious injury or death, and that most living things with the capacity of inflicting serious harm on one another have evolved inhibitory mechanisms that prevent them from doing so. As ethological studies have gotten more sophisticated, however, it has become clear that these generalizations were idealized and exaggerated. In fact animals, even members of the same species, do kill one another. There is, however, some truth to the generalization that many living things have evolved behaviors that make lethal aggression less frequent than might otherwise be expected.

Increasingly sophisticated field studies of animal behavior show that animal aggression is not limited to inter-individual events; inter-group aggression has also been documented—for example, between lion prides or chimpanzee groups. Lethal aggression, in these cases, is most likely when the groups in question consist of genetically unrelated individuals, just as within-group aggression is also significantly modulated among close relatives, as predicted by selfish gene theory.

Aggression Among Human Beings

There has been considerable research into the causes of aggression, especially among human beings. Aggression is caused by many different factors; indeed, virtually every scientific specialty has its own take on which factors are especially important. For psychoanalysts, aggression derives largely from innate human destructiveness, what Freud called thanatos, or the death instinct. Although biologists are particularly unconvinced by this approach (it is difficult to imagine a situation for which a death instinct—especially when directed toward one's self—would be selected), there are parallels between this and another instinctivist approach, best articulated by the ethologist Konrad Lorenz (1903–1989). Lorenz hypothesized that aggression has evolved in a variety of circumstances, including spacing and population control, and provides an opportunity for competition within a species, as a result of which the most fit members will emerge to produce the next generation, and also establishes a means whereby the pair bond is strengthened, when, for example, a mated pair demonstrates shared aggression against competitors.

Sociobiology and evolutionary psychology provide updated biological explanations for human and animal aggression, emphasizing the degree to which aggression is adaptive rather than somehow mandated by the genome. This approach focuses on the way particular behavior patterns are maintained and promoted in a population because they contribute to the reproductive success of individuals (and their genes), as opposed to groups or species. For example, the adaptionist evolutionary view of aggression examines such phenomena as ecological competition, male-male competition, and the role of kinship patterns in directing aggressive behavior in particular ways. It also focuses on aggression as a response to circumstances rather than an innate need. Adaptionists do not argue that aggressiveness will emerge despite affirmative constraints. Rather, proponents maintain that living things have the capacity to behave aggressively when such behavior maximizes their fitness, and to behave pacifically when that response is in their best evolutionary interest.

It should be emphasized that predatory behavior—hunting—is different from aggressive behavior. The fact that certain Australopithecines and other prehuman species were evidently meat-eaters does not in itself mean that they were aggressive. Aggressive behavior is most prominent within a species, not between species. Lions, for example, often behave aggressively toward other lions, in which case they make themselves conspicuous and threatening; by contrast, when hunting zebras, lions employ very different behavior patterns, making themselves inconspicuous until the actual attack, and not relying on bluff or other means of aggressive intimidation.

The mainstream view among social scientists is that aggression is almost entirely a response to specific circumstances. So-called frustration theory has been especially influential; it posits that whenever aggressive behavior occurs, there must be frustration, and similarly, whenever frustration occurs, it always produces aggression of some kind. Other psychological approaches focus on the role of social learning, such as conditioning theory in which aggressiveness—by groups as well as individuals—is more likely when such behavior has been positively reinforced, and less likely when negatively reinforced. In short aggression is crucially modified by its consequences.

Social psychologists, by contrast, focus on the degree to which individuals can be socialized to aggressiveness, just as sociologists examine the role of social structures (religion, family, work ethos, mythic traditions) in predisposing toward aggression. Special consideration has been given to matters of ethnic, racial, and religious intolerance. Ironically, although most scientists agree that race has no genuine biological meaning, theories that focus on the importance of stereotyping and of in-group amity, out-group enmity have gained increasing attention.

For anthropologists interested in cross-cultural comparisons of human aggression, a paramount consideration is the extent to which aggression may be functional in acquiring land, access to mates, or status, as well as in regulating population, organizing social relationships within the group, and even influencing the pressure that tribal units place upon agricultural productivity and/or human population or the wild game on which they may depend. The prehistory of human aggressiveness remains shrouded in mystery, although most specialists agree that primitive human groups engaged in substantial violence as well as cannibalism.

For many political scientists, relevant considerations include the role of rational calculations of state benefit and national power. An important underlying assumption is that states behave aggressively when it is in their perceived interest to do so, perhaps because of the prospect of enhancing their influence and power (realpolitik), minimizing potential decrements to it, or enhancing the political viability of national leaders, among other reasons. Approaches run the gamut from mathematical models created by game theoreticians to analyses of historical cycles, matters of national prestige, and economic/resource based considerations.

Aggression and Ethics

Ethical analyses of aggression are nearly as diverse as efforts to explain its occurrence. Although aggression among animals is not susceptible to ethical judgments, human aggression certainly is. Indeed ethical assessments—often negative—may be especially directed toward cases of aggression. Such judgments may be absolute, on the order of philosopher Immanuel Kant's (1724–1804) categorical imperative, which maintains that any act or aggression is acceptable only if it could be reasonably seen to be based on general principles of behavior. However situational ethics typically emphasize that aggression should be evaluated with regard to the conditions in which it occurs. Thus self-defense—whether by an individual or a group—is enshrined in most legal and moral codes, whereas aggression is widely considered to be unacceptable when it occurs without adequate provocation, or preemptively.

The degree to which such ethical judgments are supported or undermined by scientific studies is open to debate. For instance, some believe that scientific knowledge of the biological mechanisms of aggressive behavior demonstrates that cultural moderation, in the form of moral sanctions, is a continuation of nature in nurture. Others argue that the widespread presence of aggression among animals legitimates its presence among humans. In the end, the tensions between these arguments point toward granting moral judgments or values some degree of independence in assessing human behavior, although such judgments will, by necessity, be refined as science advances additional theories to explain the complexities of aggression. Finally, the discussion of whether and to what extent science and technology can be characterized as aggressive activities, although again somewhat independent of scientific research, is furthered by reflection on the scientific study of the phenomena of aggression.


SEE ALSO Darwin, Charles;Ethology;Just War;Nature versus Nurture;Sociobiology;Violence.


Barash, David P. (2001). Understanding Violence. Needham Heights, MA: Allyn & Bacon. Contains many crucial pieces concerning violence, from a variety of disciplines.

Barash, David P., and Charles P. Webel. (2002). Peace and Conflict Studies. Thousand Oaks, CA: Sage Publications. A comprehensive textbook that introduces the field of peace and conflict studies.

Eibl-Eibesfeldt, Irenaus. (1979). The Biology and Peace and War: Men, Animals and Aggression. New York: Viking. Presents traditional ethological ideas concerning aggression, with special attention to human peace and war.

Lorenz, Konrad Z. (2002). On Aggression. New York: Routledge. A readable and only slightly outdated account of the classical ethological approach to animal and human aggression.

Moynihan, Martin H., and Michael H. Robinson. (1998). The Social Regulation of Competition and Aggression in Animals. Washington, DC: Smithsonian Institution Press. A technical compendium of source material concerning causes of, and constraints upon, aggressive behavior in animals.


views updated Jun 11 2018


Aggression in humans remains a substantial social problem. A number of theories have been constructed to explain aggression, and much research has focused on factors that affect aggressive behavior.

In the ethological approach, aggression is viewed as an instinctual system built into the organism independently of external stimuli. This aggression must be released through an appropriate releasing stimulus. The most influential instinctual theory is the concept of thanatos proposed by Austrian neurologist Sigmund Freud (1856-1939). He theorized that two instinctual drives, eros (love instinct) and thanatos (death instinct), motivate human behavior. Thanatos manifests itself as aggressive behavior in daily living.

The other main theory comes from social learning and focuses on environmental influences. Albert Bandura focused on modeling processes that shape aggressive behavior and direct feedback in the form of reward and punishment. From social cognitive theorists comes the assumption that the social interpretation about which interpersonal behaviors constitute aggressive provocational retaliation is crucial for determining whether children will behave aggressively or not.


Aggression is defined as behavior aimed at causing harm or pain, psychological harm, or personal injury or physical distraction. An important aspect of aggressive behavior is the intention underlying the actor's behavior. Not all behaviors resulting in harm are considered aggression. For example, a doctor who makes an injection that harms people, but who did so with the intent of preventing the further spread of illness, is not considered to have committed an aggressive act.

Aggression can be direct or indirect, active or passive, and physical or verbal. Using these categories, human aggression can be grouped into eight classes of behavior:

  • Punching the victim (direct, active, physical)
  • Insulting the victim (direct, active, verbal)
  • Performing a practical joke, setting a booby trap (direct, passive, physical)
  • Spreading malicious gossip (direct, passive, verbal)
  • Obstructing passage, participating in a sit-in (indirect, active, physical)
  • Refusing to speak (indirect, active, verbal)
  • Refusing to perform a necessary task (indirect, passive, physical)

Direct aggression, especially physically active aggression, is more common among animals. Actors who express indirect aggression usually feel less satisfaction, but they are also less concerned about retaliation. Passive and indirect aggression is the least noxious form. Subordinates rebelling against authority figures often use it. In the family relation it is often used by children against their parents.

The Role of Biological Factors

Some theorists argue that the foundations of aggression are biological. Biological factors that influence aggressive behavior include hormones, physiological illness, and temperament.

Hormones play some indirect role in human aggression. Interaction with external stimuli may affect the threshold of aggressive behavior. Some researchers have concluded that high testosterone levels could be a result of aggressive behavior. In women, premenstrual tension syndrome is associated with a number of aggressive behaviors, such as violent crime.

People with a serious physiological illness, such as cancer, may be affected by negative mood states. These mood states may indirectly affect the aggressive behavior of individuals.

Temperament may be indirectly related to aggressive behavior. People who are impulsive are more likely to be aggressive than people who have a deliberate temperament.

Relationship to Rearing Practices

Although human aggression may have an instinctual component, aggression is modifiable by environmental factors, such as child-rearing practices and parental characteristics.

Aggressive children often develop in families with a low degree of positive interactions and a high degree of punitive reciprocity. Children in such families learn to control other family members through aggression. This model of control behavior in the home is then generalized to peers. This process thus creates aggressive children.

Research focused on parental characteristics found that mothers of nonaggressive girls tended to use the strategy of discussion to solve social problems more often than mothers of aggressive girls. Fathers of nonaggressive girls had more alternative strategies for solving social problems than fathers of aggressive girls.

Influence of Television and Other Media

Of the several different forms of media, television is one of the most influential in terms of child development. The effects of seeing violence on television has been debated among the scientists interested in child development. The main reason why watching violence on television causes violence in real world is the pervasiveness of violent programs.

There are several ways of explaining how the viewing of violence on television affects aggression in young people, including the direct effect, desensitization, and the so-called mean world syndrome. Aggression and favorable attitudes toward the use of aggression will develop if people watch a lot of violence on television. This direct effect has been a focus of research. Ross Parke and his colleagues, working in a natural setting, found that boys who viewed aggressive movies displayed an increased amount of physical and verbal aggression against other children.

According to desensitization theory, people who watch a lot of violence on television may become less sensitive to the various kinds of aggression and violence in the real world.

A third explanation for the link between television and aggression holds that some people suffer from the mean world syndrome, in which they believe that the world is as dangerous as it appears on television.

The effect of television violence on children has been debated. It is important to note that psychologists and psychiatrists involved in media studies do not suggest that violent media are the only causes of violence in society.

The Effectiveness of Intervention to Reduce Aggression

A variety of ways of handling aggression have been suggested over the years. One aspect of social learning that tends to inhibit aggression is the tendency of most people to take responsibility for their own actions. But if this sense of responsibility is weakened, the tendency to act more aggressively will increase. (In one experiment, a researcher demonstrated that persons who are anonymous and unidentifiable tend to act more aggressively than persons who are not anonymous.)

There are a number of ways that an individual can reduce aggression. As long as there is a hope that is unsatisfied, there will be frustration that can result in aggression. Aggression can be reduced by satisfying that hope.

Doing something physically exerting or watching someone else engage in aggression directly or indirectly tends to relieve built-up aggressive energies and hence reduce the likelihood of further of aggressive behavior. This is called catharsis. The catharsis hypothesis also holds that watching an aggressive behavior on television serves a valuable function in draining off aggressive energy.

It has been argued that it might be possible to reduce aggression by presenting the child with the sight of aggressive models who come to bad ends. The implicit theory is that individuals who are exposed to this sight will in effect be vicariously punished for their own aggression and accordingly will become less aggressive.

Other methods of reducing aggression that have been proposed include defusing anger through apology and providing training in communication and problem-solving skills.

Using punishment to reduce aggressive behavior is tricky. It can be effective if it is not too severe and if it follows closely on the heels of the aggressive act.

Anger Management Programs

In 1997 Albert Ellis and Raymond Chip Tafrate presented an approach to the problem of dealing with anger called rational emotive behavior therapy (REBT). This approach was designed to help people deal effectively with emotional problems and to systematically understand the roots and nature of anger. REBT deals with the problem of anger realistically. The core of REBT is unconditional acceptance of self and then continually maintaining this feeling of self-acceptance.

The Role That Peers Play

Children generally establish strong, stable, mutual affiliations with peers similar to themselves in aggression, but aggressive children have more difficulty establishing such affiliations. The interaction of peer pairs containing at least one aggressive child was characterized by more frequent, lengthy, and intense conflict regardless of the affiliate relationship characterizing the pair. Researchers found that the amount of time children spent interacting with aggressive peers predicted changes in observed and teacher-rated aggression three months later.

Peer estimation of aggression was found to be internally more consistent than self-estimation. This was true of both sexes for both the aggressive and victim version of the test. Participants seem to be more reliable when they estimate the degree to which they are the victims of others' aggression than when they estimate the degree to which they themselves are aggressive. This is particularly true for girls.

Influences of Socialization

Although growing up in a violent community is associated with aggressive behavior, the degree to which this can be considered seriously pathological has been called into question by the results of some research.



Aronson, E., T. D. Wilson, and R. M. Akert. Social Psychology. New York: Longman, 1997.

Baron R. A., and D. Byrne. Social Psychology: Understanding Human Interaction, 5th edition. Newton, MA: Allyn and Bacon, 1987.

Betsch, T., and D. Dickenberger. "Why Do Aggressive Movies Make People Aggressive? An Attempt to Explain Short-Term Effects of the Depiction of Violence on the Observer." Aggressive Behavior 19 (1993):137-149.

Buss, A. Psychology: Man in Perspective. New York: Wiley, 1973.

Dollard, John, L. W. Doof, N. E. Miller, O. H. Mowrer, and R. R. Sears. Frustration and Aggression. Westport, CT: Greenwood Press, 1980.

Ellis, Albert, and Raymond Chip Tafrate. How to Control Your Anger Before It Controls You. Toronto: Carol Publishing, 1997.

Groves, P. M., and G. V. Rebeck. Introduction to Biological Psychology, g4th edition. Dubuque, IA: William C. Brown, 1992.

Österman, K., K. Björkqvist, K. M. J. Lagerspetz, A. Kaukianen, L.R. Huesmann, and A. Fraczek. "Peer and Self-Estimated Aggression and Victimization in Eight-Year-Old Children from Five Ethnic Groups." Aggressive Behavior 20 (1994):411-428.

Pakaslahti, L., I. Spoof, R. L. Asplund-Peltola, and L. Keltikangas-Jaarvinen. "Parent's Social Problem Solving Strategies in Families with Aggressive and Non-Aggressive Girls." Aggressive Behavior 34 (1998):37-51.

Snyder, J., E. Horsh, and J. Childs. "Peer Relationships of Young Children: Affiliative Choices and the Shaping of Aggressive Behavior." Journal of Clinical Psychology 26, no. 2 (1997):145-155.



views updated May 29 2018






Aggression is defined as behavior that is intended to harm others and that is perceived as harmful by the victim. Because aggression is such a broad phenomenon, subtypes of aggression have been proposed to reconcile discrepant research findingsfor example, that not all aggression is angry. Subtypes of aggression abound, but two classifications are most important: reactive versus proactive aggression, and physical versus social aggression.

Reactive aggression is angry, impulsive, and typically occurs in response to provocation, whereas proactive aggression (sometimes called instrumental aggression ) is more cool and deliberate and is deployed to achieve a social goal. Although reactive and proactive aggression are highly correlated, they seem to be related to different correlates and developmental outcomes (Coie and Dodge 1998). Reactive aggression is related to overattributing hostility in social interactions, whereas proactive aggression is related to expecting that physical aggression will have positive outcomes. Reactive aggression is associated with parental abuse, behavior problems in the classroom, and peer rejection and victimization. Proactive aggression is related to friendship similarity and leadership, and also predicts future antisocial behavior.

Because hurtful behavior can take nonphysical forms, perhaps especially for girls, other important subtypes to consider are physical and social aggression. Social aggression is behavior that hurts others by harming their social status or friendships. This form of aggression includes malicious gossip, friendship manipulation, and verbal and nonverbal forms of social exclusion (Underwood 2003). Social aggression is sometimes called indirect or relational aggression, but the construct of social aggression acknowledges that harm to relationships can be both direct and indirect, and that social exclusion can be both verbal and nonverbal. Here again, childrens propensities to engage in social and physical aggression are highly correlated. Both social and physical aggression may take reactive or proactive forms.

Across almost all cultures that have been studied, boys and men are more physically aggressive than girls and women are. However, evidence for gender differences is much less clear for social aggression. Because base rates for girls physical aggression are so low, without a doubt girls are more socially aggressive than they are physically aggressive. However, this does not necessarily mean that girls are more socially aggressive than boys are, and research findings conflict. Future research should examine whether social aggression unfolds differently in girls groups than in boys groups.


Physical aggression emerges in the first two years of life (Tremblay et al. 2005) and may have biological correlates. Experts disagree as to whether there is a strong genetic component for physical aggression, but genes likely underlie temperamental qualities that have been shown to be related to aggression in childhood, which appears in such forms as impulsivity, negative emotionality, and reactivity. Although testosterone has long been thought to be related to physical aggression, the relation between this hormone and physical fighting is complex and at best indirect. Elevations in testosterone are more related to social ascendance than aggression specifically.

Socialization experiences may relate to a childs propensity for physical aggression. Children who experience harsh, abusive parenting may develop a bias toward interpreting ambiguous social cues as hostile, which leads them to be sensitive to slights and prone to reactive aggression. Children whose parents have an authoritarian style (punitive and low on warmth) may be more likely to have behavior and peer problems. Children who engage in coercive cycles with parents, in which the childs behavior escalates until the parent gives in, thereby reinforcing the highly noncompliant behavior, are more prone to a number of antisocial behaviors that may include physical aggression. Children may also become increasingly aggressive as a result of exposure to media violence on television or in video games, although the direction of causation is difficult to disentangle because physically aggressive children may be more drawn to violent media content.

Physical aggression is associated with a number of adjustment problems, in childhood and beyond. Children who fight are at risk for peer rejection and academic difficulties; as adolescents, they are at risk for dropping out of school, delinquency, and substance use. Although fewer girls than boys fight physically, those that do are just as much at risk for these negative outcomes (Putallaz and Bierman 2004). For girls, physical aggression in childhood is associated with adolescent childbearing, and these adolescent mothers who were aggressive as children are at heightened risk for having children with health and behavioral problems.


Although much less is known about the developmental origins of social aggression, interesting hypotheses are emerging. Children may learn the power of social aggression by watching their parents resolve marital conflicts in ways that involve triangulating others and threatening relationship harm, or by watching how parents refrain from open conflict with friends but instead malign others behind their backs. Children may also learn social aggression by observing peers or siblings, or perhaps even by seeing relationship manipulation and malicious gossip gleefully depicted in television and movies, not only those aimed at children and adolescents but also adult programming.

Engaging in high levels of social aggression and chronically being victimized are both associated with psychological maladjustment for children. Children, especially girls, who are frequently victimized report elevated levels of depression, loneliness, anxiety, and low self-concept. In addition, children who frequently perpetrate social aggression are disliked by peers, and they report feeling lonely and anxious. In young adult women, being nominated by peers as high on social aggression has been shown to be related to bulimia and borderline personality disorder. As suggested by Nicki Crick and Carolyn Zahn-Waxler (2003), high levels of social aggression may be associated with the psychological problems to which girls and women are most vulnerable.


Future research should examine how physical and social aggression are related and unfold together in both real and developmental time. Promising strategies to reduce physical aggression involve training parents to respond strategically to their children by rewarding positive behavior and not reinforcing aggression, and teaching children skills that will help them regulate emotions and form relationships. Some of these same strategies may be helpful for reducing social aggression, and adding components that address social aggression may enhance the effectiveness of violence prevention programs.


Coie, John D., and Kenneth A. Dodge. 1998. Aggression and Antisocial Behavior. In Handbook of Child Psychology, ed. William Damon. Vol. 3, Social, Emotional, and Personality Development, ed. Nancy Eisenberg, pp. 779-862,. New York: Wiley.

Crick, Nicki R., and Carolyn Zahn-Waxler. 2003. The Development of Psychopathology in Females and Males: Current Progress and Future Challenges. Development and Psychopathology 15, 719-742.

Putallaz, Martha, and Karen L. Bierman. 2004. Aggression, Antisocial Behavior, and Violence Among Girls: A Developmental Perspective. New York: Guilford.

Tremblay, Richard E., Willard W. Hartup, and John Archer. 2005. Developmental Origins of Aggression. New York: Guilford.

Underwood, Marion K. 2003. Social Aggression Among Girls. New York: Guilford.

Marion K. Underwood


views updated May 18 2018


Any act that is intended to cause pain, suffering, or damage to another person.

Aggressive behavior is often used to claim status, precedent, or access to an object or territory. While aggression is primarily thought of as physical, verbal attacks aimed at causing psychological harm also constitute aggression. In addition, fantasies involving hurting others can also be considered aggressive. The key component in aggression is that it is deliberateaccidental injuries are not forms of aggression.

Theories about the nature and causes of aggression vary widely in their emphases. Those with a biological orientation are based on the idea that aggression is an innate human instinct or drive. Sigmund Freud explained aggression in terms of a death wish or instinct (Thanatos) that is turned outward toward others in a process called displacement. Aggressive impulses that are not channeled toward a specific person or group may be expressed indirectly through safe, socially acceptable activities such as sports, a process referred to in psychoanalytic theory as catharsis . Biological theories of aggression have also been advanced by ethologists, researchers who study the behavior of animals in their natural environments. Several have advanced views about aggression in humans based on their observations of animal behavior. The view of aggression as an innate instinct common to both humans and animals was popularized in three widely read books of the 1960sOn Aggression by Konrad Lorenz , The Territorial Imperative by Robert Ardrey, and The Naked Ape by Desmond Morris. Like Freud's Thanatos, the aggressive instinct postulated by these authors builds up spontaneouslywith or without outside provocation until it is likely to be discharged with minimal or no provocation from outside stimuli.

Today, instinct theories of aggression are largely discredited in favor of other explanations. One is the frustration-aggression hypothesis first set forth in the 1930s by John Dollard, Neal Miller, and several colleagues. This theory proposes that aggression, rather than occurring spontaneously for no reason, is a response to the frustration of some goal-directed behavior by an outside source. Goals may include such basic needs as food, water, sleep , sex, love, and recognition. Contributions to frustration-aggression research in the 1960s by Leonard Berkowitz further established that an environmental stimulus must produce not just frustration but anger in order for aggression to follow, and that the anger can be the result of stimuli other than frustrating situations (such as verbal abuse).

In contrast to instinct theories, social learning theory focuses on aggression as a learned behavior. This approach stresses the roles that social influences, such as models and reinforcement , play in the acquisition of aggressive behavior. The work of Albert Bandura , a prominent researcher in the area of social learning, has demonstrated that aggressive behavior is learned through a combination of modeling and reinforcement. Children are influenced by observing aggressive behavior in their parents and peers, and in cultural forms such as movies, television, and comic books. While research has shown that the behavior of live models has a more powerful effect than that of characters on screen, film and television are still pervasive influences on behavior. Quantitative studies have found that network television averages 10 violent acts per hour, while on-screen deaths in movies such as Robocop and Die Hard range from 80 to 264. Some have argued that this type of violence does not cause violence in society and may even have a beneficial cathartic effect. However, correlations have been found between the viewing of violence and increased interpersonal aggression, both in childhood and, later, in adolescence . In addition to its modeling function, viewing violence can elicit aggressive behavior by increasing the viewer's arousal, desensitizing viewers to violence, reducing restraints on aggressive behavior, and distorting views about conflict resolution .

As Bandura's research demonstrates, what is crucial in the modeling of violenceboth live and on screenis seeing not only that aggressive behavior occurs, but also that it works. If the violent parent, playmate, or superhero is rewarded rather than punished for violent behavior, that behavior is much more likely to serve as a positive model: a child will more readily imitate a model who is being rewarded for an act than one who is being punished. In this way, the child can learn without actually being rewarded or punished himselfa concept known as vicarious learning.

The findings of social learning theory address not only the acquisition, but also the instigation, of aggression. Once one has learned aggressive behavior, what environmental circumstances will activate it? The most obvious are adverse events, including not only frustration of desires but also verbal and physical assaults. Modeling, which is important in the learning of aggression, can play a role in instigating it as well. Seeing other people act in an aggressive manner, especially if they are not punished for it, can remove inhibitions against acting aggressively oneself. If the modeled behavior is rewarded, the reward can act vicariously as an incentive for aggression in the observer. In addition, modeled aggression may serve as a source of emotional arousal.

Some aggression is motivated by reward: aggressive behavior can be a means of obtaining what one wants. Another motive for aggression is, paradoxically, obedience. People have committed many violent acts at the bidding of another, in both military and civilian life. Other possible motivating factors include stressors in one's physical environment , such as crowding, noise, and temperature, and the delusions resulting from mental illness . In addition to the acquisition and instigation of aggression, various types of reinforcement, both direct and vicarious, help determine whether aggression is maintained or discontinued.

Researchers have attempted to learn whether certain childhood characteristics are predictors of aggression in adults. Traits found to have connections with aggressive behavior in adulthood include maternal deprivation, lack of identification with one's father, pyromania , cruelty to animals, and parental abuse. A 22-year longitudinal study found patterns of aggression to be established by the age of eightthe aggressive behavior of both boys and girls at this age was a strong predictor of their future aggression as adults. Other factors cited in the same study include the father's upward social mobility, the child's degree of identification with parents, and preference for violent television programs.

See also Television and aggression

Further Reading

Aggression and Peacefulness in Humans and Other Primates. New York: Oxford University Press, 1992.

Aggressive Behavior: Current Perspectives. New York: Plenum Press, 1994.

Bandura, Albert. Aggression: A Social Learning Analysis. New York: Prentice-Hall, 1973.

Of Mice and Women: Aspects of Female Aggression. New York: Academic Press, 1992.


views updated May 29 2018


Because members of a population have a common niche, there is a strong potential for conflict. Agonistic behavior is displayed when there is a contest that will determine which competitor gains access to a particular resourcefor example, food or a mate. The encounter involves both threatening and submissive behavior, and may also involve tests of strength. More often, the contestants engage in threat displays that make them look large or fierce, usually through exaggerated posturing and vocalizations. Eventually one animal will stop threatening and end with a display of submission or appeasement, in effect calling an end to the fight.

Much agonistic behavior includes ritual activity so that serious harm does not occur to either combatant. In many circumstances, escalated violence over ownership of a mate or commodity is less an adaptive behavior than it is an exchange of signals, whether threatening or submissive. The agonistic signals provide information about the likely intentions and levels of commitment of the senders, as well as the relative fighting ability if escalation occurs. Any future interactions between the same two animals is usually settled much more quickly and in favor of the original victor.

Aggression can be used in a number of different interactions, such as those concerning territorial defense, potential mates, parent-offspring communication, social integration, and food. Conflict resolution usually occurs at short sender-receiver distances. The senders perform actions with tactical and signal functions, and the receivers make decisions based on all the information pooled from the cues and all secondary sources.

Intra- and Interspecific Competition

Conflicts usually arise between two more or less equal individuals who need the same resources to secure or increase their fitness. Both would like to obtain the resource with minimal fighting, so both want the other individual to back down. However, the two opponents are rarely of equal fighting ability or resource-holding potential. Each combatant wants to convey that it is the superior fighter and so uses displays of aggression. However, each one must also assess the other's fighting ability relative to its own. Thus both individuals are senders and receivers simultaneously. The number of signals and tactical acts, and the truthfulness in the information being conveyed, must have something to do with the resolution of the conflict.

Types of Conflict

Intraspecific competition.

When the conflict is intraspecific , between members of the same species, dominance hierarchies come into consideration. For example, placing several hens together that are unfamiliar with each other results in pecking and skirmishing. Eventually, a pecking order is established in which the most dominant hen, the alpha hen, controls the behavior of all the other hens, mostly through threat rather than actual pecking. The beta (second-ranked) hen does the same and so on to the lowest hen, the omega. The advantage of the top hens is that they are assured access to food resources. There is an advantage for the lower-ranked hens as well, because the system ensures that they will not waste energy or risk injury in futile combat.

Interspecific competition.

In the event that two or more species in a community rely on similar resources, they may be subject to interspecific competition. Actual fighting between members of two different species is termed interference competition, whereas the use or consumption of the "shared" resources is called exploitative competition. As population densities increase and resources such as food or nesting sites decrease, there is bound to be an increase in competition between the species. The same tactics of agonistic signaling apply here despite the variation in numbers and types of signals among the different species.

Strategies for Victory

Individuals in conflict can employ a number of strategies when assessing their opponent and the minimal level of aggression necessary to be the victor.

Hawk vs. Dove.

One theory, termed "hawk versus dove," helps explain why two animals do not always fight over the commodity that is sure to increase the fitness of the winner. Assuming the contestants are equal, there are two clear choices regarding the sought-after commodity: fight (as an aggressive hawk would do) or exhibit peaceable displays (as a dove would be more apt to do). When two hawks meet, they immediately fight over the commodity, with the loser suffering fight injuries as well as the cost of having lost the resource. Because the contest is assumed to be symmetric, each hawk wins half of its battles with other hawks. When a hawk meets a dove, the hawk becomes aggressive and the dove flees. Two doves will both use some costless exchange of displays to decide who gets the commodity and who leaves peacefully.

The take game.

Another contest that has been observed is a take game, which again involves two strategies: to be passive or to cheat. The passive animal minds its own business. The cheat, however, increases its own fitness at the expense of the fitness of others. The fishing activity of gulls and terns offers a good example. Some (passive) birds will concentrate solely on catching their own fish. Others (the cheats) will give up some of their own fishing time to monitor the success of other birds. When another bird catches a fish, the cheat will chase after the bird until the fish is dropped and then steal the fish. There is an advantage to cheating only if the bird can steal more fish than it would catch on its own.

The significance of this game is that once any cheats appear, the population will become most stable once all the organisms cheat. Evolution will have therefore lowered the average fitness of the population, a nonintuitive outcome given the assumption that evolution generally improves the average fitness of populations. It is only where evolution models a more passive approach to the acquisition of resources that populations enjoy improvements in their average fitness. However, many evolutionary models lead to lower average fitness, and this simply reflects the costs of competition.

The war of attrition.

Certain games employ strategies drawn from a continuous range of possibilities. A classic example is the war of attrition, in which two opponents compete by selecting an amount of strategic investment to be played during the particular confrontation. Neither opponent knows before the confrontation what level of investment the other has chosen. During the confrontation, the opponent that chose a larger investment wins. The investment might be the amount of time each is prepared to display to the other, or it might be how much energy the players put into the display.

It is unlikely that many animals meet the conditions for a symmetric war of attrition, where all players suffer the same cost of display and would obtain the same benefit in winning. Usually the rate at which costs accumulate will not be the same for any two players. Also, the commodity over which they are fighting is likely to have different fitness values for each player. The critical issue thus becomes which player stands to gain the most from the commodity and lose the least while trying to win it. If the two animals knew at the outset which one was on superior footing, then there would be no confrontation and the animal that stood to lose the most would leave immediately.

However, such complete and accurate information is rarely available as two opponents face each other. The "game" that is then played is called an asymmetric war of attrition. A player that suspects it has the winner role will likely select a higher investment, while a player that suspects it has the inferior role will likely select a lower investment. Of course, it is possible that both players will decide they occupy the same role. These considerations emphasize the uncertainty inherent in this game. Depending on the presumptions of both animals, the confrontation may briefor it may prove to be a long and vigorous fight.

see also Behavior; Behavioral Ecology; Dominance Hierarchy; Social Animals.

Danielle Schnur


Bradbury, Jack W., and Sandra L. Vehrencamp. Principles of Animal Communication. Sunderland, MA: Sinauer, 1998.

Campbell, Neil A. Biology, 3rd ed. San Francisco, CA: Benjamin/Cummings Publishing Company, 1993.

Maynard Smith, J. Evolution and the Theory of Games. Cambridge, U.K.: Cambridge University Press, 1982.


views updated Jun 11 2018


Aggression is behavior or a behavioral urge with the object of threatening or harming primarily members of one's own species. Several theories attempt to explain aggression.

Theories of aggression

The theory of instinct in ethology, as proposed by Konrad Lorenz (19031989), supposes that humans, like other biological creatures, are so constituted that they either continuously or periodically produce physiological energies that must seek outlet in certain kinds of species-specific aggressive behavior. Other ethologists argue that although innate genetic codes, as well as neural and hormonal processes, account for an aggressive disposition, there is no reason to assume the existence of aggressive energies. All ethologists agree, however, that aggression has arisen in the course of evolution and serves the same basic functions in animals and humans in regulating the intercourse between members of a species, although the regulation involves more psychological and cultural aspects with humans than with other animals.

This assumption is endorsed by sociobiology, first systematized by Edward O. Wilson (1929), which studies the social behavior of humans using evolutionary methods. Like ethologists, sociobiologists presume an innate aggressive disposition in humans, but sociobiologists define innateness as the measurable probability that aggressiveness will develop in a species within a specified set of environments, not the certainty that it will develop in all kinds of environments.

The psychoanalytic drive theory of Sigmund Freud (18561939) resembles the instinct theory of Lorenz in the assumption that innate drives represent physiological energies. Freud departs from Lorenz, however, by assuming that the activity of the drives does not result in species-specific behavior patterns. Freud concluded that two drive complexes embodied in human beings constitute the basic sources of all human behavior; these were the life-building Eros and the life-demolishing Thanatos, with aggression, directed both outwards against others and inwards against oneself, as its central feature.

The theory of needs by Henry Murray (18931988) put forward a list of about twenty presumably universal human needs, among them aggression. In need theory there is no place for physiological energies. If a certain need, such as aggression, is dominant within a person in many different situations, it also appears as a personality trait.

The frustration theory, first presented by John Dollard (19001980) and his colleagues, explains aggression in a different way. Although aggression probably is a universal human disposition, aggressive behavior arises only as a reaction to incidents where purposeful behavior is blocked. Because this theory can only explain some kinds of aggression, it was modified by Leonard Berkowitz (1926), who argued that aggression might still be a basic reaction to frustration.

The theory of learning proposed by Albert Bandura (1925) and others places the origin of aggression solely in the social environment in assuming that aggressive behavior is learned during life history. Aggression is learned either because it is rewarded, or at least not sanctioned, and thereby reinforced. It may also be learned by observing aggressive behavior at home, on the streets, or from the media and entertainment industries, which show that aggression is worthwhile because it gets results, with aggressive people becoming models for imitation.

There might be elements of truth in all the theories, depending on which kind of aggression is in question in which kind of context: physical or mental, intended or reactive, instrumental or spontaneous, hostile or teasing, assaulting or defending, directed toward others or toward oneself, status demonstration, group conflict, sex, age, personality, and so on. Innumerable circumstances may influence the causes of aggression and aggressive behavior may involve a wide spectrum of explanations.

Aggression as evil

Anger is a faithful partner to aggression. For medieval Christians wrath was one of the seven deadly sins. Only God could pass judgment on righteous and unrighteous deeds, and in many cases anger arises when an offense is experienced as unjust. This tenet might have left deeper marks on culture than people are aware of, showing up in the widespread condemnation of anger and aggression. While moderate anger can instigate constructive action, blind anger often leads to destructive aggression. Yet to psychology and biology even furious anger and aggression cannot in itself be sinful, let alone evil. Because aggression is probably an unavoidable human trait, be it conceived of as innate or acquired, from a scientific point of view the very occurrence of aggression cannot be malice, and the absence of aggression cannot be kindness. For conceptions of good and evil to make scientific sense, evil must be viewed as the absence of an attempt to control aggression, thus preventing love to prevail.

In the animal kingdom human beings alone are able to curb their natural impulses and their learned habits, at least to some extent, and to listen to the voice of conscience, moral qualities that can be learned and even taught using psychological techniques. The attempt to curb aggressive behavior might not succeed, which in itself is not evil because it is bound to happen now and then. Evil is only the absence of the attempt to curb aggression, and the absence of remorse at not doing so. In psychological terms, such remorse could be called guilt in a more general sense than the concrete failure of the attempt, due to the conscience, which in its innermost voice tells a person that every concrete failure is a sin against the general good or a sin against love understood as the basic source of bonding and attachment in personal and social life. In this way, the concrete failure to curb aggression makes a person guilty against humankind, not only against the victim of the concrete failure. If a person grasps this idea of aggressive behavior, and yet in defiance and pride does not attempt to control aggression or seek atonement for the sin of failing to control it, then this person might be called evil. If so, probably all people are evil now and then, and many are evil fairly often. However, control can take the shape of inhibition and aggression can be turned inwards, which is not always mentally healthy either.

see also altruism; evil and suffering; psychology; sociobiology


bandura, albert. aggression: a social learning analysis. englewood cliffs, n.j.: prentice-hall, 1973.

berkowitz, leonard. aggression: its causes, consequences, and control. new york: mcgraw-hill, 1993.

dollard, john; doob, leonard w.; miller, neal e.; mowrer, orval hobart; and sears, robert r. frustration and aggression. new haven, conn.: yale university press, 1939.

freud, sigmund. beyond the pleasure principle (1920), trans. c. j. m. hubback. london: hogarth press, 1953.

lorenz, konrad. on aggression (1963), trans. margaret kerr wilson. new york: harcourt, 1966.

murray, henry a., et al. explorations in personality: a clinical and experimental study of fifty men of college age. new york: oxford university press, 1938.

wilson, edward o. sociobiology. cambridge, mass.: harvard university press, 1975.

boje katzenelson