Instinct

Concepts of instinct

Instinct in ethology

Instinct in comparative psychology

BIBLIOGRAPHY

Reference to the concept of instinct is to be found in most of the major writings on social psychology and on behavior in general. However, the nature of such reference has not always been acceptance or approval. The career of the term “instinct” in the history of psychology has been a checkered one. Like the phoenix, instinct has been “consigned to the flames” only to rise again. Like Proteus, it has survived by repeatedly adopting new forms.

Instinct in common usage. Instinct has led a less troubled existence in common usage, and it is here that one might find reasons for both its vicissitudes and its persistence in academic psychology. In common speech, instinct and instinctive occur in a variety of situations and with a variety of meanings. We say that someone acts instinctively if his act is done without thought or deliberation but rather on impulse. We speak of knowing, believing, or feeling something instinctively and thereby mean that we cannot recall having learned or having been told about it but rather that the knowledge, belief, or feeling just arose within us. We say of someone that he has an instinct for, say, mathematics or stage direction, meaning that he is by nature good at these things. We speak of maternal or creative instincts when referring to behavior that seems to be the expression of a deep and perhaps characteristically human urge. We describe someone as acting out of an instinct of revenge, meaning that revenge was his motive. We speak of blind instinct when someone cannot say why he acted in a certain way or what the purpose of his action was. We might say that someone was obeying the herd instinct if he followed the crowd instead of his own judgment. We might claim to have found our way home by instinct, meaning that we did not arrive home by accident, or by the conscious use of a map or memory, but were guided in some unconscious way.

This list of how instinct and instinctive are used every day in reference to human thought and action is by no means exhaustive, and many more differences and shades of meaning could be added if we were to extend the list to the behavior of animals. But it should be clear already that there is no one meaning common to all these usages. There is continuity between the several meanings in the sense that no usage is completely unrelated to at least one of the others. We have what Wittgenstein referred to as “family resemblances” between words, “a complicated network of similarities overlapping and criss-crossing: sometimes overall similarities, sometimes similarities of detail” ([1953] 1964, p. 32). In spite of the range of meanings that instinct and instinctive have in everyday language, usage seldom leads to misunderstanding; context and custom usually furnish whatever is necessary to convey the meaning that is intended on a particular occasion.

Concepts of instinct

Science and philosophy traditionally aim at a greater degree of precision or rigor than is characteristic of the statements of ordinary language. A scientist or philosopher might object that many of the uses of instinct are loose and vague, that underlying the varieties of use there must be a single concept of which instinct is the name, but of which the ordinary man is only dimly aware. The inconsistency of ordinary language will be avoided by making the underlying concept explicit and by defining instinct in terms of it. We find frequent reference in psychological writing to the concept of instinct and numerous attempts to define instinct in a precise way.

However, the variability of the definitions that scholars have proposed for instinct is almost as great as the variety of its uses in ordinary language. Any new theory of, or outlook on, behavior is likely to incorporate a concept, category, or distinction that is matched by at least one of the uses of instinct in ordinary language. Scholars have tended to settle on the ordinary language use or uses that suit their purposes, and they define instinct accordingly. Hence the persistence of the word in psychology. But there has also been a tendency to assume, albeit tacitly, that an explicit definition of instinct in terms of one of its meanings somehow incorporates its other meanings as well; at least the other meanings tend to be retained regardless of the definition—hence, in part, the difficulties that psychologists encounter in using the term. To assume that all, or most, of the many meanings of instinct can be gathered into one precise concept in fact leads to the reverse of precision, to the blurring of distinctions, to the confounding of questions, and hence to misunderstanding and confusion. A detailed analysis of the several kinds of uses to which instinct has been put—demarcation of the several kinds of facts, concepts, questions, and explanations with which instinct has been associated—would be a move in the direction of greater precision. Until such analysis has been made it is unlikely that questions about the relations between the different meanings of instinct and the possibility of their being reduced to one concept can be profitably discussed. In what follows, some examples will be used to illustrate the hybrid character of the instinct concepts and the controversies to which these concepts have led.

Darwin’s concept

Most modern theories of instinct are derived from Darwin as much as from anyone else. However, Darwin was well aware of the ambiguity of instinct; he declined to give an unequivocal definition of instinct on the grounds that “several distinct mental actions are commonly embraced by the term …” ([1859] 1964, p. 184). And he used instinct in a number of ways: to refer to what impels a behavior pattern such as bird migration, to a disposition like courage or obstinacy in a dog, to feelings such as sympathy in man, and to stereotyped and species-characteristic behavior patterns such as hive building in the bee.

Nevertheless, some of Darwin’s discussion of instinct, in particular some of the inferences he drew from facts that he cited, indicates that he tended at times to think of instinct as a single concept that united a number of distinct notions. For instance, it was essential to his argument that instincts be hereditary, but he assumed that being hereditary implies, and is implied by, development without the mediation of experience. Now if instinct is defined in terms of both inheritance and independence of experience, it follows that one can be inferred from the other if we know that we are dealing with a phenomenon to which this notion of instinct is applicable. The connection is a logical one—true by definition. But how are we to know that we are dealing with a phenomenon to which this definition applies, unless we already know, as a matter of fact, that this phenomenon is both hereditary and independent of experience? For it is at least conceivable that something could be inherited and yet depend on some sort of experience for its development and that something could develop independently of experience, in the sense in which this is usually understood, and yet not be inherited. Intelligence has a hereditary basis but also requires experience for its development. Whether or not a particular pattern of behavior is both inherited and independent of experience cannot be decided by inference from evidence in favor of only one of these possibilities; the question can be decided only on the basis of observation.

In fact, in compiling material for the Origin of Species, Darwin had little detailed information about how behavior patterns and dispositions develop in individual animals, and he apparently made little effort to obtain it. Such information would not have been as obviously relevant to his argument—that behavior has evolved by natural selection—as the kinds of facts he did document: evidence for the evolution of behavior, the inheritance of behavior, and the adaptiveness of behavior. A restricted and precise scientific concept could have been formulated on the basis of these facts, but ideas about ontogeny and subjective content (absence of reason, foresight, and so on) traditionally associated with instinct adhered to Darwin’s use of the term and, hence, were part of the concept he passed on to those who followed him.

In the Descent of Man (1871) Darwin employed instinct mainly in the sense of natural urge or compulsion to action. An instinct in this sense was a unitary or autonomous entity of which there are a specific number in each kind of animal. Such an instinct has three main aspects; the nature of the impulse, the behavior it impels, and the goal toward which the impulse, and hence the behavior, is directed. In fact it is by its goal more than anything else that such an instinct is identified; whether a behavior, such as a pecking movement, belongs to a particular instinct will be judged not on the basis of form alone (stereotyped or not) but rather on whether it is the kind of behavior that in the circumstances will tend to bring about acquisition of the goal of the instinct—the building of a nest, the securing of food, the defeat of a rival, and so on. Unfortunately there can often be more than one version of what the goals of behavior are, and it is a questionable assumption that a classification of behavior patterns according to the goals they serve corresponds to a set of internal unitary driving systems. These are difficulties which adherents of this concept of instinct had to contend with. However, if one assumes the existence of a certain number of distinct natural impulses in an animal the possibility arises that there can be interactions between them. In social behavior, Darwin said, we often see the simultaneous arousal of incompatible tendencies—for example, self-preservation instincts and parental instincts—and so we are led to the notion of conflict between instincts and to the notion that instincts can differ in strength and that one can overcome another [seeConflict, article onpsychological aspects]. Darwin examined the long-maintained idea that the strength of an instinct is determined by its tendency to promote the attainment of pleasure or the avoidance of pain; he agreed that there are some instincts to which this idea applies, but that in the case of others, “it is probable that instincts are presently followed from the mere force of inheritance, without the stimulus of either pleasure or pain” ([1871] 1948, p. 477). As this discussion suggests, Darwin anticipated most of the questions and confusions associated with the term “instinct” in the writings of students of behavior who succeeded him.

Freud’s concept

Instinct in Freud’s writings refers to a natural impulse or innate driving force. Freud made much use of the notion of conflict, in particular, conflicts between instinct and experientially acquired features of mental life. He assumed the existence of two broad categories of instinct in man, aggression and sex, each of which was to be considered as consisting of, or differentiating into, a number of subinstincts [seeAggression, article onpsychological aspects].

According to Freud (1900), the goals of overt behavior are not always sufficient to reveal its instinctive basis, since the social, convention-ridden life of man involves suppression or distortion of many of the natural expressions of instinct. Only the techniques of psychoanalysis, such as the analysis of word associations and dreams, can reveal the true inner dynamics of human behavior—the ways in which the instincts and their conflicts express themselves. Freud’s concept of instinct was derived from clinical observations but was an “armchair” concept in that it contained little direct empirical reference, and no attempt was made to subject it to direct empirical analysis. It also contained contradictory elements that led to some inconsistency in its use. Freud wrote at times as though instinct were a kind of blind energy, at least analogous with the energy of physics, the dynamics of which follow quasi-mechanical laws; at other times he wrote as though instinct were something that could have intention and could employ strategies.

A good part of Freud’s later thinking about instinct was devoted to developing theories of how instinctive pressures are transformed and integrated through experience into socially compatible patterns of thought and action. Subsequently, some psychoanalysts such as Karen Horney and her colleagues (e.g., Horney 1937), placed even greater emphasis on the role of society and culture in the shaping of the structure and dynamics of the mind. They did not deny the existence of instincts as biologically grounded forces affecting behavior, but they took the position that the available facts allot a greater contribution to social forces in the generation of psychological conflicts, psychoses, and so forth, than was allowed by the speculative notions of classical Freudian theory about the functioning of instincts [seeHorney].

McDougall’s concept

Perhaps the most influential champion of instinct in psychology was William McDougall, whose Introduction to Social Psychology (1908) was one of the first textbooks of social psychology. In it he employed a concept of instinct as a base for an extremely persuasive comprehensive theory of behavior, a theory that was credited with the dual achievement of bringing a new and elegant synthesis to the subject matter of psychology and of giving psychology the status of a natural science based on biological principles. The biological principles were those of Darwinism. The core of McDougall’s thinking about instinct was the conception, given widespread currency by Darwin and his followers, of instincts as hereditary and unitary behavior systems driven by internal goal-directed impulsions. To this McDougall grafted the traditional (particularly Kantian) conception of the tripartite division of mind into faculties of knowing, feeling, and willing. He defined instinct as “an inherited or innate psycho-physical disposition which determines its possessor to perceive, and to pay attention to, objects of a certain class, to experience an emotional excitement of a particular quality upon perceiving such an object, and to act in regard to it in a particular manner, or, at least, to experience an impulse to such action” (McDougall 1908, p. 25 in the 1936 edition). Conveniently at hand was the three-part division of neurophysiological systems, and McDougall took what to him was the obvious step of locating the cognitive aspect (knowing) of instinct in sensory pathways, the affective aspect (feeling) in associative pathways, and the conative aspect (willing) in motor pathways. The connections between the three parts of an instinct were thus thought of as neural, but McDougall insisted that the dynamics of instinct are not purely mechanical, after the manner of reflexes. He insisted that an instinct is a psychophysical system, by which he meant that mental phenomena—the awareness of feeling, emotion, and impulse—play an essential and active role in determining instinctive action.

According to McDougall, instincts are capable of modification during the life of an individual within limits that differ from species to species, man having wider limits than other animals. But the possibility of modification through experience pertains only to cognition and conation (1908, p. 29 in the 1936 edition). Hence identification of the distinct primary emotions is the one valid method of discovering what, and how many, instincts there are. According to McDougall, such an analysis of instincts is necessary before one can make significant progress in understanding the nature of complex derived or secondary patterns of behavior or mental phenomena. He presented a list of what he considered to be the primary emotions and hence the principal instincts in man. He attempted to justify his list on Darwinian principles by reference to the probable adaptive significance, and hence evolutionary basis, of each instinct.

McDougall’s success established a fashion for instinct and other Darwinian ideas in psychology. Lists of instincts multiplied in psychological writings, and the concept took root in such fields as economics (e.g., Veblen 1914) and the study of wars (e.g., Trotter 1916). However, as the lists multiplied, so did their variety. Different writers based their lists on different criteria: primary emotions, purposive behavior patterns, the number of species-characteristic behavior patterns, and so on. Even those who adhered to McDougall’s argument and based their analyses only on primary emotions were rarely in agreement. Introspection, or whatever other means of judgment were used, yielded different lists for different people, and there was no recognized way of deciding who was right and who was wrong. [seeTrotter; Veblen.]

In part McDougall’s own practice encouraged the indiscriminate and vague use of instinct against which he had argued in the introduction to his book. For, according to his theory, with the exception of reflexes all behavior is instinctive or has an instinctive base. Also, his concept of instinct appeared to provide a bridge between at least two kinds of explanation of behavior: explanation in terms of causes and effects and explanation in terms of intentions and actions. But the age-old question about the relations between these two kinds of explanation was not solved by talk about psychophysical processes. McDougall’s own concept was, in fact, vague—a composite of largely un-analyzed ideas that were not really fitted together. Furthermore, the concept and the theory of which it was a part were speculations whose connections with facts were left, to a large extent, indeterminate and hence were difficult to pin down for empirical test. At least so it appeared to those who led what became known as the “anti-instinct revolt.”

The anti-instinct revolt

The first significant shot in the anti-instinct revolt was fired by Dunlap in a paper that appeared in 1919. According to Dunlap, McDougall’s theory was vitiated because it contained the notion of subjective purposiveness and hence involved recourse to unobservable phenomena. On the premise that science deals only with what is publicly observable and with concepts defined solely in terms of what is publicly observable, McDougall’s theory was judged to be unscientific. Other critics attacked the use of the idea of inborn behavior patterns; they cited evidence that encouraged the view that all but the simplest reflexes are molded by experience. By and large, instinct theories proved no match for new and rival movements, such as behaviorism, that tough-mindedly insisted on the priority of hard facts and on the value of experimental methods.

However, while discarding instinct as a scientific term, the behaviorists retained some of the ideas that had been connoted by it. For instance, the concept of primary biological need persisted in drive-reduction theories of learning, and concepts of impulses or subjective purposiveness covertly continued despite efforts to bring “operational” purity to the theoretical language of psychology (Taylor 1964). Nevertheless, the opponents of instinct, no less than its champions, seemed to have assumed that its many facets rose or fell together, that to affirm or question independence of experience, or subjective purposiveness, was to affirm or question instinct in all its senses. In fact, behaviorists, with perhaps a few exceptions, did not apply their methods to a number of questions and facts with which the instinct theorists had concerned themselves; for example, the adaptive significance of species-characteristic behavior patterns, spontaneity in behavior, the relation of behavioral similarities and differences to questions about evolutionary relationships.

Instinct in ethology

A resurgence of concern with biological aspects of behavior brought about the most recent rejuvenation of instinct. Beginning in the late 1930s the ethologists, led by Konrad Lorenz and Nikolaas Tinbergen, accused both the proponents and opponents of instinct of failure to pay sufficient attention to large classes of facts about animal behavior. Ethologists proceeded to develop ideas about instinctive behavior that purportedly were based on, and took account of, such facts. The aim was to make instinct an objective concept and the study of instinct an objective science.

The background of ethology was classical zoology (comparative morphology and evolution) and amateur natural history. The facts from which ethologists started were the contents of detailed inventories of species-characteristic behavior patterns, observations of the sequential patterning and frequency distributions of occurrences of such patterns, the taxonomic distribution of variations of behavior patterns, and the biological functions of species-characteristic behavior patterns.

Lorenz and Tinbergen

According to Lorenz, ethology was founded on the discovery of a “distinct and particulate physiological process … a certain type of innate genetically determined behaviour patterns” (1950, p. 221). This type of behavior pattern was referred to as an “instinctive activity” (Instinkthandlung). It was characterized as (a) stereotyped, (b) possessed by all members of at least one sex of a species, (c) innate in the sense of genetical inheritance, (d) innate in the sense of being unlearned, (e) endogenously controlled—once set in motion it is completed without further mediation by peripheral stimuli, and (f) the goal and terminus of a variable sequence of “appetitive” behavior. In an early paper Lorenz (1937, p. 329) also included the idea of being craved (Angestrebtwerden) in his definition of the instinctive activity. To explain the timing of attempts to perform an instinctive activity, Lorenz postulated that spontaneous endogenous generation and accumulation of “energy,” specific to each kind of instinctive activity, initiates and drives the appropriate appetitive behavior until “discharged” in performance of the instinctive activity. Performance of the activity is precipitated, or “released,” by an encounter with some specific external stimulus that engages an “innate release mechanism.”

Here again we encounter a concept of instinct that groups together a number of distinct characteristics. Was this grouping a matter of definition or a matter of fact? There is no doubt that there are stereotyped, environment-resistant, species-characteristic behavior patterns that terminate variable chains of searching activities; and inter-species comparison of variations in the forms of such behavior patterns indicates that they do reflect genetic affinity. But that Lorenz had at his disposal the kinds of facts about ontogeny that could justify the use of the term “unlearned,” and the kinds of facts about physiological control that could justify descriptions such as “spontaneous,” “endogenous,” and “independent of peripheral stimulation” for even one instinctive activity, is disputable. On the other hand, the facts of neuro-physiology disqualify the energy model from being anything more than a picturesque way of describing certain facts about behavior.

Other ethologists became dissatisfied with the unphysiological character of Lorenz’ energy model and also with the atomistic character of his picture of instinctive activities and their control. Tinbergen (1951), for example, observed that the behavior patterns serving any one of the primary biological functions, such as nutrition or reproduction, tend to be carried out in a sequence in which more and more specific types of appetitive behavior succeed one another, only the final one of which terminates in performance of a stereotyped “end act.” Transition from one type of appetitive behavior to the next is effected by an animal’s encountering a particular releasing stimulus. At each stage of the sequence, with the exception of the last, there are usually several alternative types of appetitive behavior that can follow; which type occurs on any occasion will depend upon which of the several kinds of possible releasing stimuli is encountered. Thus a hunting predator might begin its search for prey with behavior that is not specific to the capture of only one type of prey; it then switches to the appropriate one of a set of prey-catching patterns as soon as it sees or smells a particular type of prey. The prey-catching behavior will, in turn, vary according to the avoiding measures taken by the prey and be switched to the stereotyped pattern specific for killing the prey once the prey is caught. Underlying such a sequence, Tinbergen pictured a mechanism consisting of a hierarchically arranged system of nervous centers and innate releasing mechanisms that channel the flow of “motivational impulses” of which the behavior is the expression. According to Tinbergen’s scheme, there is a hierarchical system corresponding to each of the primary biological functions, and he referred to each such system as an instinct. Activation of the reproductive instinct, then, would mean production of motivational impulses from the highest part of the reproductive hierarchy and the expression of these impulses in courting, territorial fighting, copulation, nest building, parental behavior, and so on, depending at any time on the level of the hierarchy at which the impulses were accumulating and the releasing stimuli available. Incidentally, Tinbergen did not believe that there were grounds for postulating a “social instinct.”

Tinbergen’s theory, like McDougall’s, related the behavior of an animal to a small number of distinct systems which were inborn and hence the product of natural selection. But Tinbergen avoided the inclusion of subjective phenomena by accounting for the purposive aspects of behavior with a purely mechanical or quasi-mechanical model. Nevertheless, the empirical status of this model was as questionable as McDougall’s, although for different reasons. In spite of the quasi-physiological terms used to describe the model, many of its key properties were known not to have any close correspondence with physiological reality. In fact, the structure of the hierarchical scheme was based on a classification of overt patterns according to their functional characteristics—the biological ends they promote—and analysis of these classes into temporal and sequential patterns. The only solid evidence in support of the theory, then, was contained in the overt patterns it purportedly accounted for, and it was begging a crucial question to assume a simple correspondence between this evidence and the underlying physiology. But the description of overt behavior was not entirely anterior to the theory; for instance, the idea that instinct involves the generation of energy and the consumption of this energy in performance of a fixed action pattern diverted attention from evidence that the goals of certain patterns are not “end acts” or their “releasers” but specific stimulus situations per se.

Evaluation. The instinct theories of Lorenz and Tinbergen were of positive value in that they revived interest in questions and facts about the survival value, the taxonomic relevance, and the temporal and sequential patterning of animal behavior. But they suffered the same type of fate as their predecessors, and for the same sort of reason: they overreached themselves. Unsympathetic critics (e.g., Lehrman 1953; Schneirla 1956) accused them of adducing unobservable entities, of failure to distinguish and pay sufficient attention to the facts of overt behavior, physiology, and ontogeny and even to phyletic differences. In later writings ethologists tried to meet these objections by reformulating their ideas in terms of operationally defined concepts. For instance, “action specific energy” or “motivational impulses” were replaced by “specific action potentiality” or “tendency”—terms that were supposed to refer only to probabilities of occurrence, judged on the basis of observation, of behavior patterns (see Beer 1963-1964).

However, if one limits oneself, in talking about a particular subject matter, to concepts defined solely in terms of that subject matter, one places considerable restriction on the kinds of things that can be said about it. One can make generalizations about, and describe relationships between, items of the subject matter, but one cannot explain such generalizations or relationships by referring them to a wider field of knowledge. That the restrictions of operationism are uncongenial to at least some ethologists is evident from inconsistencies in their use of certain terms. “Tendency,” for instance, is defined as “probability of occurrence,” but that a particular probability of occurrence is such-and-such is sometimes explained as due to the strength of the relevant tendency. For tendency to convey anything here, it must refer to something other than probability; it will be covertly doing the sort of work that action specific energy was doing in the instinct theory. The same kind of problem is encountered in the way the concept of conflict is used. Alongside, and sometimes confused with, the operational definition of conflict as equality of probabilities of incompatible responses, are two uses that preserve patterns of explanation of older conceptions, conflict in the sense of simultaneous arousal of internal mechanisms underlying incompatible responses and conflict applied to opposition of selection pressures. Some of the ingredients of the instinct theories of ethology thus persist, although they are often disguised in forms that stand in the way of both consistent operationism and explicit presentation of explanatory hypotheses in forms that could be subjected to testing.

Thorpe

Recently an attempt to reformulate an ethological concept of instinct has been made by Thorpe (1956). According to Thorpe, the central notion of this concept is that of “internal drive”; in addition, instincts are characterized as consisting of (a) an inherited system of coordination, (b) more or less rigid inherited action patterns, and (c) more or less rigid releasing mechanisms. He explains “inherited” in terms of current ideas about genetic coding and eschews “preformation-ism” by saying that what is encoded in the genes is a set of instructions that determines what an organism takes from its environment in the way of materials and stimulation to build up an instinctive mechanism. Following Lorenz (1961; see also 1965) he maintains that “we are justified in saying that the behaviour pattern is innate in the sense that the complexity which it displays arises primarily from the instructions in the germ cell and not from instructions which are contributed by the environment” (Thorpe [1956] 1963, p. 17). Both Thorpe and Lorenz consider this formulation a valuable refinement of the concept of innateness. Allusion to the concept of “information” of cybernetics gives an air of mathematical precision, even though the exact meaning to be given to “instructions” is anybody’s guess. But it is difficult to see how this concept of “innate” adds a useful tool either to thinking about the inheritance of behavior or to thinking about the development of behavior. Indeed, the concept promises to perpetuate the confusion between these two classes of problems that has vitiated much of the past discussion of “nature versus nurture.” [seeCyberneticsandInformation theory.]

Thorpe is aware that ambiguity has attended use of the word “innate.” However, he places the ambiguity not between inherited and unlearned but between “(1) inherited or genetically fixed and therefore characteristic of the species; (2) internally co-ordinated; [and] (3) internally motivated” (ibid., p. 15). Instinct, according to Thorpe, is innate in each of these senses. There is space here only for a remark about the third one.

According to Thorpe, “there is within the drive itself some inherent directiveness, some extremely restrictive purposive influence, perhaps identical (with) …expectancy and insight …” (p. 49), and purpose here is to be understood as “a striving after a future goal retained as some kind of image or idea” (p. 3). This thesis represents yet another attempt to build a bridge between the two apparently contradictory patterns of explanation of behavior: in terms of intentions or motives on the one hand and causes and mechanisms on the other (e.g., McDougall). Thorpe is probably right in his belief that the relation between these patterns of explanation poses one of the central problems for students of behavior. We seem to find it impossible to exclude from our descriptions of behavior categories of behavior identified by goals that, in some sense, are goals for (entertained by) the animal (consider fleeing, for example), and yet, as scientists we seem to be committed to the attempt to reduce such description to language devoid of teleological or subjective reference. Unfortunately, Thorpe’s discussion of the problem does not solve it. If a solution is to be found, it will probably not come before the several concepts and questions involved have been clearly sorted out and their logic mapped. Thorpe, however, trades on the ambiguities of terms like “drive,” “motivation,” and “purpose” with the result that all the difficulties are preserved. At least so it has appeared to his tough-minded readers on the western side of the Atlantic.

Instinct in comparative psychology

By and large, the American psychologists who study animals other than humans reflect the legacy of behaviorism or the patterns of thought of which behaviorism was an expression: they tend to be pragmatic, positivistic, operational, and hostile to theories of instinct. However, their attitudes on theories of instinct have not all been the same, and as we have noted, the drive theorists preserve one of the connotations of instinct, albeit under different names.

Lashley (e.g., 1938) was one comparative psychologist for whom instinct had considerable attraction and who perceived that the anti-instinct revolt directed most of its attack on only one aspect of what was a composite notion. Lashley thought that there was still a place for a concept of instinct, but true to the spirit of positivism, his approach was essentially objective and experimental.

Lashley distinguished species-characteristic behavior patterns that are reactions to specific stimuli from variable, searching types of behavior that could be considered reactions to the absence of some form of stimulus situation. The former he chose to refer to as instinctive activities and the latter as “reactions to a deficit.” Instinctive activities were, furthermore, to be distinguished from reflexes by being “determined by the pattern of organization of the stimulus” rather than by the effect of stimuli of a particular modality on receptor endings at a particular locus. Explanation of variations in the “excitability of the sensori-motor mechanism and of reaction to a deficit” he referred to as “the problem of the activation of the instinct.”

Parallels between Lashley and Lorenz are evident here, even though they arrived at their ideas independently and by quite different routes. There are equally striking contrasts. Whereas Lorenz made his categories the basis of an over-all theory of behavior, Lashley aimed at sorting out a particular problem and describing it in terms that would suggest the kinds of physiological approaches that might throw light on it. For Lashley the study of instinct comprised problems of sensory organization, the integration of sensory input and motor output, the growth processes that effect the establishment of the sensorimotor mechanisms, and the roles of factors like hormone secretion in the activation of the sensorimotor mechanisms. He developed no theory and postulated the existence of no unobservable entities; he did not suggest that what might be found to be true for one instinct would necessarily hold true for others. His category of instinctive activities was intended to be a pragmatic one.

The question of the innateness of instinctive activities was one that Lashley passed over with little comment, even though he was aware of the difficulties it posed and of the fact that the use of instinct would inevitably be associated with the notion of innateness in one or both of its senses. Beach went so far as to say, “When all the criteria which supposedly differentiate instinctive from acquired responses are critically evaluated, the only one which seems universally applicable is that instincts are unlearned” (1955, p. 405). Beach, in this paper, was renewing the attack on the use of instinct in psychology and including Lashley’s use of the term. According to Beach, it is generally assumed by psychologists who think in terms of instinct that behavior can be assorted into two mutually exclusive and collectively exhaustive categories : learned behavior on the one hand, inherited and/or unlearned behavior on the other. Even those psychologists who, like Z. Y. Kuo, reject instinct seem to accept the dichotomy between inherited and acquired elements of behavior, in maintaining that inherited elements are few and simple and the rest learned. Beach argued that such a dichotomy is indefensible. If the dichotomy is taken to be between learning and heredity, there is abundant evidence to show, for instance, that learning has a hereditary basis and, hence, that mutual exclusion does not obtain. If the dichotomy is taken to be between learning and its absence, we have one category that is defined by exclusion from another that is poorly understood—logically a dubious state of affairs, to say the least. Moreover, inheritance and learning are only two of many kinds of influences that can contribute to the ontogeny of behavior. Beach’s message was that the psychologist should resist the temptation of his armchair and should try to settle questions about the genetics and ontogeny of behavior in the only way that they can be, by appropriate observations and appropriate experiments: “When [such] methods have been applied to the various types of behaviour which today are called ‘instinctive’ the concept of instinct will disappear, to be replaced by scientifically valid and useful explanations” (1955, p. 409).

Lehrman (1953), Schneirla (e.g., 1956), and Hebb (1953) have been as tough-mindedly insistent as Beach that understanding of how behavior develops in different animals will be advanced only by investigation unrestricted by a priori ideas about how many different kinds of processes there are. Lehrman, for instance, summed up his position as follows: “Any instinct theory which regards ‘instinct’ as immanent, preformed, inherited, or based on specific neural structures is bound to divert the investigation of behavior development from fundamental analysis and the study of developmental problems. Any such theory of ‘instinct’ inevitably tends to short-circuit the scientist’s investigation of intraorganic and organism-environment developmental relationships which underlie the development of ‘instinctive’ behavior” (1953, p. 359).

In spite of continuities that exist between past and present thinking, instinct is seldom used with any of its older theoretical connotations in the writings of present-day ethologists and comparative psychologists. If it occurs at all, it is usually as a loose but often convenient label for a rather ill-defined class of species-characteristic and stereotyped behavior patterns about which questions of causation, ontogeny, and so forth remain, for the most part, open.

The ambition to arrive at an over-all theory of animal behavior no doubt persists and perhaps will some day be realized in a synthesis that will not involve confusions between facts and questions of different sorts. It may be that a concept of instinct will have a place in future syntheses. But unless history is to repeat itself yet again, such a concept would do well to pay heed to the lessons to be learned from its forerunners: they thrived on blurred distinctions, but to their ultimate undoing.

C. G. Beer

[Directly related are the entriesEthology; Evolution; Genetics, article ongenetics and behavior; Imprinting. Other relevant material may be found inCommunication, animal; Drives; Emotion; Motivation; Nervous system; Psychoanalysis; Psychology, article oncomparative psychology; Sexual behavior, article onanimal sexual behavior; Sympathy and empathy; and in the biographies ofDarwin; Lashley; Mcdougall.]

BIBLIOGRAPHY

Beach, Frank A. 1955 The Descent of Instinct. Psychological Review 62:401-410.

Beer, C. G. 1963-1964 Ethology: The Zoologist’s Approach to Behaviour. Tuatara 11:170-177; 12:16-39.

Darwin, Charles (1859) 1964 On the Origin of Species. Cambridge, Mass.: Harvard Univ. Press.

Darwin, Charles (1871) 1948 The Descent of Man and Selection in Relation to Sex. In Charles Darwin, The Origin of Species and The Descent of Man. New York: Modern Library.

Dunlap, Knight 1919 Are There Any Instincts? Journal of Abnormal Psychology 14:307-311.

Freud, Sigmund (1888-1938) 1959 Collected Papers. 5 vols. Authorized translation under the supervision of Joan Riviere. Vol. 5 edited by James Strachey. International Psycho-analytic Library, Nos. 7-10, 34. New York: Basic Books; London: Hogarth. → A 10-volume paperback edition was published in 1963 by Collier.

Freud, Sigmund (1900) 1953 The Interpretation of Dreams. Volumes 4-5 of The Standard Edition of the Complete Psychological Works of Sigmund Freud. London: Hogarth; New York: Macmillan. → First published as Die Traumdeutung.

Hebb, D. O. 1953 Heredity and Environment in Mammalian Behaviour. British Journal of Animal Behaviour 1:43-47.

Horney, karen 1937 The Neurotic Personality of Our Time. New York: Norton.

Lashley, K. S. 1938 The Experimental Analysis of Instinctive Behavior. Psychological Review 45:445-471.

Lehrman, Daniel S. 1953 A Critique of Konrad Lorenz’s Theory of Instinctive Behavior. Quarterly Review of Biology 28:337-363.

Lorenz, Konrad Z. 1937 Uber die Bildung des Instinkt-begriffes. Naturwissenschaften 25:289-300, 307-318, 324-331.

Lorenz, Konrad Z. 1950 The Comparative Method in Studying Innate Behaviour Patterns. Pages 221-268 in Society for Experimental Biology, Physiological Mechanisms in Animal Behaviour. Symposium No. 4. New York: Academic Press.

Lorenz, Konrad Z. 1961 Phylogenetische Anpassung und adaptive Modifikazion des Verhaltens. Zeitschrift fur Tierpsychologie 18:139-187.

Lorenz, Konrad Z. 1965 Evolution and Modification of Behavior. Univ. of Chicago Press.

Mcdougall, William (1908) 1950 An Introduction to Social Psychology. 30th ed. London: Methuen. → A paperback edition was published in 1960 by Barnes and Noble.

Schneirla, T. C. 1956 Interrelationships of the “Innate” and the “Acquired” in Instinctive Behavior. Pages 387-452 in L’instinct dans le comportement des animaux et de I’homme, by M. Autuori et al. Paris: Masson.

Taylor, Charles 1964 The Explanation of Behaviour. New York: Humanities Press.

Thorpe, William H. (1956) 1963 Learning and Instinct in Animals. 2d ed., rev. & enl. Cambridge, Mass.: Harvard Univ. Press.

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

Trotter, Wilfred (1916) 1953 Instincts of the Herd in Peace and War: 1916-1919. Edited by R. W. Chapman. New York: Macmillan. → First published as Instincts of the Herd in Peace and War.

Veblen, Thorstein 1914 The Instinct of Workmanship and the State of the Industrial Arts. New York: Macmillan.

Wheeler, William M. (1920-1921) 1939 On Instincts. Pages 37-70 in William M. Wheeler, Essays in Philosophical Biology. Cambridge, Mass.: Harvard Univ. Press. → First published in the Journal of Abnormal Psychology.

Wilm, Emil C. 1925 The Theories of Instinct. New Haven: Yale Univ. Press.

Wittgenstein, Ludwig (1953) 1964 Philosophical Investigations; Philosophische Untersuchungen. New York: Macmillan. → The title and the text are in both German and English.

Instinct

Examples of instinct

The role of instinct in learning

Instincts can be exploited

Instinct and learning: a continuum

Resources

An instinct is a stereotyped species-typical behavior that appears fully functional the first time it is performed, without the need for learning. Such behaviors are usually triggered by a particular stimulus or cue, and are not readily modified by subsequent experience. For instance, a kangaroo rat instantly performs an automatic escape jump maneuver when it hears the sound of a striking rattlesnake, even if it has never encountered one before. Clearly, instinctive behaviors play an important role in survival, but our understanding of the forces that promote and guide their development in living animals is in fact quite limited.

Examples of instinct

Researchers of animal behavior, ethologists, first named the stereotyped species-typical behaviors exhibited in particular circumstances “fixed-action patterns,” later called instincts. A cocoon-spinning spider ready to lay its eggs builds a silk cocoon in a particular way, first spinning a base plate, then the walls, laying its eggs within, and finally adding a lid to seal the top. The spider performs all these actions in a specific sequence, and, indeed, cannot spin its cocoon in any other way. If the spider is relocated after having spun the base plate, she will still make the walls, deposit the eggs (which promptly fall out the bottom), and spin the lid for the top. When ready to begin the next cocoon, if the spider is returned to her original base plate, she will nonetheless begin by spinning a new base plate over the first, as if it were not there.

Many fixed-action patterns occur in association with a triggering stimulus, sometimes called a releaser. Baby gulls respond to the sight of their parent’s bill by pecking it to obtain food. The releaser here is a bright red spot on the parent’s bill; neither the shape nor the color of the adult’s head have a significant influence on the response. When a female rat is sexually receptive, rubbing her hindquarters (the releaser) results in a stereotypical posture known as lordosis, in which the front legs are flexed, lowering the torso, while the rump is raised and the tail is moved to one side (a fixed-action pattern). A male rat who encounters a female in lordosis experiences another releaser and initiates copulation. Neither sequence requires any prior experience on the part of the animal.

The role of instinct in learning

Imprinting

In another classic study of instinctive behavior, ethologist Konrad Lorenz (1903–1989) showed that baby ducks and geese, which closely follow their mother on early forays away from the nest, could also be induced to follow a substitute. The baby birds would form an attachment to any individual present they saw moving after they hatch, regardless of that individual’s species identity. Young birds that had thus imprinted on Lorenz followed him everywhere as they matured, and as adults, were observed to court humans, in preference to members of their own species.

Lorenz concluded that imprinting represented a kind of preprogrammed learning, guided by a mechanism that under normal circumstances would not be corrupted by individuals of the wrong species. In the natural situation, imprinting would facilitate the babies’ social attachment to their mother, which later allows them to recognize appropriate mating partners.

Critical periods

Bird song is a largely species-specific behavior performed by males to establish and maintain their territories and to attract females. Many songbirds develop their mature songs through a process involving a critical period when, as nestlings, they hear their fathers’ song. The juvenile bird does not sing until the following spring, when it begins to match its immature song to the one it heard. If the nestling is prevented from hearing adult song during this critical period, it will never develop a species-typical song. There may also be a strongly instinctive aspect to what may be learned during the critical period; most birds cannot produce every song heard during that time, but appear to be selective toward those produced by other members of their species.

Instincts can be exploited

Some animals have evolved the capacity to take advantage of the reliable, instinctive behavior of others. Avian brood parasites, including the North American cowbird and the European cuckoo, exploit the parental behavior of other birds and lay their eggs in the host’s nest. The unwitting host feeds the interloper’s hatchlings, which are often bigger than its own, and thus may represent a greater releaser of the powerfully instinctive feeding behavior of the parents. The adult brood parasite is literally parasitizing the parental behavior of the host bird, for it exerts no further parental investment in its offspring, leaving them instead in the care of the host.

Instinct and learning: a continuum

Many people who study animal behavior argue that the term “instinct” tells little about the real mechanism that underlies the behavior. It indicates only that the behavior is relatively closed to modification by experience—nothing more. Since nervous system tissues are soft, delicate, and often very complex, understanding the operation of these structures in producing behavior presents a great challenge. This, combined with the role of experience in producing many superficially “instinctive” behaviors, makes things even more difficult.

Many behaviors held up as examples of instinct, however, are shown to have an experiential component: for instance, as new gull chicks continue to peck at billlike objects, the accuracy of their pecking improves and the kinds of bill-like objects they will peck at are increasingly restricted. Thus, the wide variety of behavioral patterns observed in living organisms surely represents a continuum, from those not much influenced by learning to those that are greatly influenced by it; a strict “nature versus nurture” dichotomy is probably too simplistic to describe any animal behavior.

The answer to “Under what conditions should a behavior be genetically closed, and when should a provision be made for learning?” seems to be related to the situation’s predictability in nature. When it is crucial that the correct response to some occurrence be carried out the first time (like a kangaroo rat faced with a striking rattlesnake), natural selection would favor a

KEY TERMS

Brood parasite —An animal that deposits its eggs or offspring into the nest of another individual (often of a different species) to be cared for by that individual.

Critical period —A developmental phase in the life of a young animal, usually with a measurable beginning and end, during which some crucial experience must occur if the animal is to develop normally.

Ethologist —A scientist of animal behavior, with particular focus on instinctive behaviors.

Fixed-action pattern —Triggered by a particular cue or stimulus, fixed-action patterns appear as a sequence of programmed behaviors which are performed to completion once they have been activated.

Releaser —The cue or stimulus that acts as a signal to induce a behavior in an animal.

fairly rigid, infallible program to underlie an appropriate response. The existence of a reliable relationship between some environmental cue and a biologically appropriate response permits the development of a releaser for triggering the “right” reaction the first time, whether to a predator, potential mates, or one’s own offspring.

Resources

BOOKS

Alcock, John. Animal Behavior: An Evolutionary Approach. 4th ed. Sunderland, MA: Sinauer, 1989.

Campbell, N., J. Reece, and L. Mitchell. Biology. 5th ed. Menlo Park: Benjamin Cummings, Inc. 2000.

PERIODICALS

West, Meredith J., Andrew P. King, and Michele A. Duff. “Communicating about Communicating: When Innate Is not Enough.” Developmental Psychobiology 23 (1990): 585-98.

OTHER

Science a Go Go. “Basic Instinct not so Basic after All” <http://www.scienceagogo.com/news/basic_instinct.shtml> (accessed November 29, 2006).

University of Illinois at Urbana-Champaign “The Emergence of Instinct” <http://faculty.ed.uiuc.edu/g-cziko/wm/03.html> (accessed November 29, 2006).

Susan Andrew

INSTINCT

Descriptive Analysis. The term instinct has been used, both in the scholastic philosophical tradition and by some scientific students of animal behavior, to refer to certain complex animal behavior patterns, e.g., hunting, nest building, and the tending of offspring. In these and similar examples, the complexity of the action is thought to exceed that of a direct stimulus-response or sensationappetition sequence, but to fall short of intelligent or rational foresight and planning. Rough criteria are as follows: instinctive behavior involves the entire organism, not merely an isolated receptor-effector mechanism; it is exhibited with some uniformity by all members of a species (or specific subgroup, e.g., worker bees), and its appearance may be distinctive of the species or group; its performance depends on the appropriate physical maturation, but does not require mimicry, trial-and-error activities, or other forms of learning. Such behavior is almost always adaptive, i.e., of positive advantage to the survival of the individual or its species.

Although these criteria have a rough value, their scientific precision and significance have been seriously questioned. To say that certain behavior patterns are unlearned, species-specific, and adaptive does not distinguish them from the more inclusive metabolic processes. To say that a behavior pattern is innate is to ignore the biological theory that genes, not characters, are transmitted from one generation to the next. The development of an organism's anatomic, metabolic, and behavioral traits involves the interaction of its genetic constitution and its environment; consequently, the distinction of innate and learned behavior patterns is softened to the point that some authors speak of genetically controlled propensities to learn rather than of innate behavior patterns. The prominent borderline phenomenon of "imprinting" is of similar significance. Imprinting is the tendency, e.g., of young birds, for a short, definite interval after hatching, to accept and follow a diverse variety of parent substitutes. Such performances are on the border between learning processes more extended in time and purely innate behavior.

Relation to Vis Aestimativa. In the philosophy of Saint thomas aquinas, the estimative power (vis aestimativa ) is one of four interior sensory powers necessary for the life of a perfect animal. The others are the imagi nation, the central sense, and the memory. Although references such as those to a "perfect" animal seem to give this position a deductive or rationalist tone, relevant factual materials are available for its inductive support:(1) The external sensation of at least some animals is quite like that of men. (2) Animals act with respect to objects that are neither gratifying nor unpleasant to the external senses, e.g., sight, touch, and smell. Birds are said to choose nesting materials that, though not attractive to sight or touch, are appropriate for nest construction, so that the choice serves the survival of that species of birds.(3) Such activities, as exhibited by the members of a particular species, exhibit a degree of uniformity. (4) But they also exhibit some plasticity or variability and are not altogether stereotyped. Consequently, what needs explanation is the order or pattern of the sequence of actions and not any mechanical repetition of identical behavioral elements. (5) The performance of these activities is likely to vary with the seasons and with the organic condition of the animal; it is not an automatic response to an external stimulus.

The interpretive principles employed in the analysis of these data include the following theses: (1) One knows, by observation and analogy, that such behavior flows from knowledge and appetite. (2) In cases in which such behavior cannot be explained by the knowledge gained through the external senses, one may rightly infer the appropriate interior sense. (see senses.)

The various data are consequently explained by the existence of a distinct internal sense power (the estimative) capable of apprehending the concrete usefulness of particular sequences of actions. The power is said to be innately determined (diversely within various species) to recognize certain organism-environment groupings as desirable and others as undesirable. Inasmuch as the proper object of this sense power is the total organism environment grouping, both plasticity and uniformity are accounted for. Similarly included within this proper object is the contemporary state of the organism itself, so that the dependence of instinctive activity upon seasonal and individual variations in metabolic state also is explained.

Critical Evaluation. The explanatory value of such statements as "the bird returned to its nest because of its homing instinct" and "the sheep flees the wolf because its estimative power is innately determined to recognize that particular organism-environment grouping as undesirable" have been called into question by students of scientific methodology. One important objection is that such explanations are really uninformative tautologies, i.e., they simply reformulate the data they pretend to explain. What is a homing instinct? If the philosopher can give no other answer than "the power by which the bird returns to its nest," the criticism seems accurate.

Another way of putting this criticism is to ask for some additional means of confirming the presence of a "homing instinct," or an "estimative power." Philosophers who hold a generally Thomistic position tend to reply with a negative argument, viz, one showing that instinctive behavior cannot be explained in terms of tropisms or reflexes and thus must be accounted for by the estimative power or some analogue for it. The formal requirements for an argument of this sort are impressive; e.g., it must be shown that the alternatives considered exhaust all possible alternatives. Argumentative rigor of this level has not actually been sought in past discussions of this topic. However, a number of interesting points have been made in illustration of weaknesses of any "mechanistic" explanation of animal behavior: (1) Reflex behavior lacks spontaneity or autonomy; it is controlled by outside stimuli. Reflex action exhibits a mechanical, off-on, relation to outside stimulation, rather than the dependence on internal events characteristic of instinctive behavior. (2) Reflex action is stereotyped or invariable in form, and so incapable of explaining the adaptive plasticity of instinctive behavior. Reflex behavior shows no tendency to improve with repeated performance as do many forms of animal behavior. From this sort of evidence it is argued that animal behavior cannot be explained in terms of a concatenation of neuromuscular reflexes and therefore must be explained in terms of some cognitive or conscious awareness of the form and purpose of the animal's activity, by the animal itself.

This last sort of argument seems to assume, however, that mechanistic theories are themselves invariable in form. In the third quarter of the 20th century, neurologists are not limited to summing the consequences of simple reflex acts, but have demonstrated a variety of facilitating, inhibiting, and correlating neural mechanisms whose activities, in ensemble, are not stereotyped and stimulus bound. At the same time, mechanism of a rigid and parochial sort is nowhere regarded as a philosophically viable explanation of animal behavior. Empiricist schools, which may be the nearest living relatives of past mechanist schools, are in fact critical of mechanism's pretensions completely and dogmatically to solve the problems of animal behavior.

Perhaps the most commendable aspect of the Thomistic explanation of instinctive activity in terms of the functioning of an estimative power is its emphasis on the really novel complexity of the phenomena in question. Instinctive behavior is not a topic on which one expects much illumination from any form of monism or exaggerated dualism. It is not a topic that is emphasized in the philosophies of atomists or Cartesians. Its appearance among the problems considered in the Thomistic theory of knowledge is a tribute to the complexity and richness of this theory, which permits cross-level, nuanced analyses where simple reductionist alternatives would seem to ignore relevant detail and significant form.

See Also: intelligence.

Bibliography: r. g. busnel, ed., Acoustic Behavior of Animals (New York 1963). j. f. donceel, Philosophical Psychology (2d ed. New York 1961). j. j. dreher and w. e. evans, "Cetacean Communication" in Marine Bio-Acoustics, ed. w. n. tavolga (New York 1964). g. p. klubertanz, The Discursive Power (Saint Louis 1952). w. kÖhler, The Mentality of Apes, tr. e. winter from 2d ed. (New York 1926; repr. 1959). a. portmann, Animals as Social Beings, tr. o. coburn (New York 1961). a. roe and g. g. simpson, eds., Behavior and Evolution (New Haven 1958). e. wasmann, Instinct and Intelligence in the Animal Kingdom, tr. from 2d. ed. (Saint Louis 1903).

[a. e. manier]

Instinct

An instinct is a stereotyped, species-typical behavior that appears fully functional the first time it is performed, without the need for learning . Such behaviors are usually triggered by a particular stimulus or cue, and are not readily modified by subsequent experience. For instance, a kangaroo rat instantly performs an automatic escape jump maneuver when it hears the sound of a striking rattlesnake, even if it has never encountered a snake before. Clearly, instinctive behaviors play an important role in survival, but our understanding of the forces that promote and guide their development in living animals is in fact quite limited.

Classic examples of animal instinct

Researchers of animal behavior, ethologists, first named the stereotyped, species-typical behaviors exhibited in particular circumstances fixed action patterns, which were later called instincts. A cocoon-spinning spider ready to lay its eggs builds a silk cocoon in a particular way, first spinning a base plate, then the walls, laying its eggs within, and finally adding a lid to seal the top. The spider performs all these actions in a specific sequence, and, indeed, cannot spin its cocoon in any other way. If the spider is relocated after having spun the base plate, she will still make the walls, deposit the eggs (which promptly fall out the bottom), and spin the lid for the top. When ready to begin the next cocoon, if the spider is returned to her original base plate, she will nonetheless begin by spinning a new base plate over the first, as if it were not there.

Many fixed action patterns occur in association with a triggering stimulus, sometimes called a releaser. Baby gulls respond to the sight of their parent's bill by pecking it to obtain a tasty morsel of food. The releaser here is a bright red spot on the parent's bill; neither the shape nor the color of the adult's head have a significant influence on the response. When a female rat is sexually receptive, rubbing of her hindquarters (the releaser) results in a stereotypical posture known as lordosis, in which the front legs are flexed, lowering the torso, while the rump is raised and the tail is moved to one side (a fixed action pattern). A male rat who encounters a female in lordosis experiences another releaser and initiates copulation. Neither sequence requires any prior experience on the part of the animal.

The role of instinct in learning

Imprinting

In another classic study of instinctive behavior, ethologist Konrad Lorenz showed that baby ducks and geese , which are observed to closely follow their mother on their early forays away from the nest, could also be induced to follow a substitute. The baby birds would form an attachment to whatever individual was present as they opened their eyes and moved about after hatching, regardless of that individual's species identity. Young birds that had thus imprinted on Lorenz followed him everywhere as they matured, and as adults, these birds were observed to court humans, in preference to members of their own species.

Lorenz concluded that imprinting represented a kind of preprogrammed learning, guided by a mechanism that under normal circumstances would not be corrupted by individuals of the wrong species. In the natural situation, imprinting would facilitate the babies' social attachment to their mother, which later allows them to recognize appropriate mating partners.

Critical periods

Bird song is a largely species-specific behavior performed by males in their efforts to establish and maintain their territories and to attract females. Many songbirds develop their mature songs through a process involving a critical period when, as a nestling, the bird hears the song of its father. The juvenile bird does not sing until the following spring, when it begins to match its immature song to the one it heard from its father during its critical period. If the nestling is prevented from hearing adult song during the critical period, it will never develop a species-typical song. Evidently, there is also a strongly instinctive aspect to what may be learned during the critical period; most birds cannot produce every song heard during that time, but appear to be selective toward songs that are produced by other members of their species.

Instincts can be exploited

Some animals have evolved the capacity to take advantage of the reliable, instinctive behavior of others. Avian brood parasites , including the North American cowbird and the European cuckoo, exploit the parental behavior of other birds and lay their eggs in the host's nest. The unwitting host feeds the interloper's hatchlings, which are often bigger than its own, and thus may represent a greater releaser of the powerfully instinctive feeding behavior of the parents. The adult brood parasite is literally parasitizing the parental behavior of the host bird, for it exerts no further parental investment in its offspring, leaving them instead in the care of the host.

Instinct and learning: a continuum

We use the term instinct to describe species-typical behavior that is seemingly performed without aid of prior experience, but what we seem to mean is that the animal moves and behaves as if mysterious and unknown forces were guiding it. Many people who study animal behavior argue that the term instinct is not ultimately helpful because it tells us little about the real mechanisms underlying behavior. The use of the term indicates only that the behavior is relatively closed to modification by experience—nothing more. Since nervous system tissues are soft, delicate, and often very complex, understanding the operation of these structures in producing behavior presents a great challenge. This, combined with the role of experience in producing many superficially "instinctive" behaviors, makes things even more difficult.

Many behaviors held up as examples of instinct are shown to have an experiential component: for instance, as new gull chicks continue to peck at bill-like objects, the accuracy of their pecking improves and the kinds of bill-like objects they will peck at are increasingly restricted. Thus, the wide variety of behavioral patterns observed in living organisms surely represents a continuum, from those not much influenced by learning to those that are greatly influenced by it; a strict "nature versus nurture" dichotomy is probably too simplistic to describe any animal behavior.

The answer to the question "Under what conditions should a behavior be genetically closed, and when should a provision be made for learning?" seems to be related to the situation's predictability in nature. When it is crucial that the correct response to some occurrence be carried out the first time (like a kangaroo rat faced with a striking rattlesnake), natural selection should favor a fairly rigid, infallible program to underlie an appropriate response. The existence of a reliable relationship between some environmental cue and a biologically appropriate response permits the development of a releaser for triggering the "right" reaction the first time, whether to a predator , potential mates, or one's own offspring.

Resources

books

Alcock, John. Animal Behavior: An Evolutionary Approach. 4th ed. Sunderland, MA: Sinauer, 1989.

Campbell, N., J. Reece, and L. Mitchell. Biology. 5th ed. Menlo Park: Benjamin Cummings, Inc. 2000.

periodicals

West, Meredith J., Andrew P. King, and Michele A. Duff. "Communicating about Communicating: When Innate is Not Enough." Developmental Psychobiology 23 (1990): 585-98.

Susan Andrew

KEY TERMS

Brood parasite

—An animal that deposits its eggs or offspring into the nest of another individual (often of a different species) to be cared for by that individual.

Critical period

—A developmental phase in the life of a young animal, usually with a measurable beginning and end, during which some crucial experience must occur if the animal is to develop normally.

Ethologist

—A scientist of animal behavior, with particular focus on instinctive behaviors.

Fixed action pattern

—Triggered by a particular cue or stimulus, fixed action patterns appear as a sequence of programmed behaviors which are performed to completion once they have been activated.

Releaser

—The cue or stimulus that acts as a signal to induce a behavior in an animal.

Instinct

An instinct is an innate, preprogrammed behavior that is genetically determined. Instinctive behaviors do not vary much within a species and are usually performed in similar, often stereotyped, ways. The acquisition of instinctive behaviors is not dependent on the environment in which an individual is raised, or on interactions with other members of its species. For example, individuals that are removed from their natural habitat and placed in isolation nevertheless develop the instincts typical to their species. Behaviors in which instinct often plays a significant role include mate recognition, courtship rituals, predator avoidance or defensive behavior, food-gathering behavior, parental care behaviors, and self-grooming.

Instinct is often contrasted with learning . Learned behaviors are shaped by experience and by the environment. Practically no behaviors, however, are purely the result of either instinct or learning. Most behaviors are the product of both, involving contributions from both genes and environment. Many behaviors that seem instinctive can be modified by experience, and many supposedly learned behaviors show biases that can be accounted for only by innate factors.

One type of instinctive behavior is called a fixed action pattern . A fixed action pattern describes a series of actions that is initially triggered by a stimulus, and then carried out to completion. Fixed action patterns are completed even though the behaviors are no longer necessary or no longer make sense.

The classic example is the egg-retrieval instinct of the gray lag goose. If a gray lag goose suddenly notices that one of her eggs is outside the nest, she rolls it back to her nest with a series of highly stereotyped head and neck motions. Even if the egg is removed (by a researcher) while the goose is in the middle of this behavior, she follows the sequence to completion. The trigger for a fixed action pattern is also called a releaser.

The advantage of instinctive behaviors is that they are much less costly than behaviors acquired through learning. Learning takes more time and energy, and also requires extensive nervous system resources. Generally, species with small brains behave more instinctively, where as those with larger brains rely more on learning. In addition, learning simply is not necessary or advantageous in many situations. It is helpful only where flexibility is important. In other circumstances, instinctive behaviors are highly adaptive and sufficient.

Instinctive behaviors are particularly suited to predictable aspects of the environment. An instinct of baby gull chicks, for example, is to peck at the red spot on the beak of adult gulls. This elicits feeding behavior from the parent. For the baby gull, there is no advantage to having to learn such a tactic.

Similarly, the fear of poisonous snakes in certain species of birds is instinctive. The motmot preys on small snakes, and young birds are attracted to these as potential food items. However, they also have an instinct to avoid snakes with a red and yellow banded coloration, which characterizes the highly poisonous coral snake. This highlights another big advantage of instinctive behaviors: Individuals know how to respond even if they are encountering a given stimulus for the first time. It is not surprising, then, that instinctive behaviors are often more prevalent in newborn or young individuals than in older ones.

Instinctive behaviors often weaken over time. In gull chicks, for example, it has been shown that newly hatched young are fairly undiscriminating. Food-begging behavior is triggered by any object that is long and narrow and that has a colored spot at the end. This object does not have to be a gull beak or even be attached to something that resembles an adult gull head. In older chicks, however, greater resemblance to an adult gull is required to elicit begging behavior.

Because of their relative simplicity, cues that trigger instincts can be taken advantage of by other species. Brood parasites are bird species that lay their eggs in the nests of other species, thereby sparing themselves the time and energy that would be required to raise those offspring. Examples of brood parasites include the cowbird and the cuckoo. The host parents feed the intruders because the baby cowbirds or cuckoos are able to produce the necessary triggers to elicit the parent's feeding instinct. These include making noisy hunger calls, stretching their necks high up out of the nest, and opening their beaks wide. In many cases, brood parasite offspring have evolved to produce triggers that are much more extreme and dramatic than those of the host's own young. As a consequence, the young brood parasites get fed preferentially in the nest.

Mating instincts are another category of innate behaviors that are frequent targets of the deceptive machinations of other species. In fireflies, for example, courtship typically consists of species-specific flashing by male fireflies followed by flashing replies from interested females. However, there is a certain species of predatory firefly that mimics the female reply of a different species in order to attract males as prey items.

In another species, the bolas spider, individuals release scents that resemble the pheromones (molecules that are used in chemical communication between members of a species) of female moths. Males who respond instinctively to this scent are caught as prey. Finally, certain flower species, including some tropical orchids, release female bee pheromones in order to attract male bees for pollination. This is one example in which learning can modify an instinctive behavior: Male bees that have encountered deceptive orchids repeatedly learn to avoid them.

see also Behavior; Behavioral Ecology.

Jennifer Yeh

Bibliography

Alcock, John. Animal Behavior, 4th ed. Sunderland, MA: Sinauer Associates, 1989.

Gould, James L., and William T. Keeton. Biological Science, 6th ed. New York: W.W. Norton, 1996.