THEORIES OF DEVELOPMENT

Why are humans the way they are? Why is it that the abilities of children seem so different than those of adults? What can one do to help children become fully developed adults? These are the kinds of questions that theorists of human development try to answer.

As it is easy to imagine from questions that are so broad, the answers theorists offer are equally broad, typically telling more about people in general than about what any one person is likely to do on a particular day. Furthermore, given such questions, the answers theorists arrive at are not always the same. In some cases this is because different theorists study different aspects of human development; in other cases it is because different theorists do their work using different sets of assumptions.

These differing assumptions reflect theoretical debates about four things. First, they reflect a debate about what in fact one should look at in order to measure the course of human development—should it be someone's actual behavior or the presumed internal psychological processes that might be reflected in behavior? Second, theorists debate how best to portray humans—are humans autonomous, self-directed individuals or ones acting largely in response to external events? Third, theorists differ as to the generalizability of their findings—is there one theory that explains the development of all people in all places at all times or are there many theories, each specific to a historical time and place? Finally, theorists differ as to the actual methods that should be used to divine the answers to all of these questions.

One useful way to understand these different approaches to the study of human development is to think of them as reflecting relatively distinct world-views. A worldview is not a theory but something larger. It represents a set of assumptions that a theory may draw upon to serve as the foundation of that theory's investigations. Three worldviews are evident in the work of developmental theorists. They are referred to as the Mechanistic Worldview, the Organismic Worldview, and the Contextualist Worldview. Theories that share the same worldview, even if they are not studying the exact same thing, are nevertheless said to belong to the same family of theories.

The Mechanistic Worldview

Theories built on a Mechanistic Worldview reflect a belief that behavior and behavior change are predictable, lawful phenomena that can, theoretically at least, be fully understood through the use of systematic, objective empirical research methods (empirical meaning that the methods rely on observation or experimentation). Secondly, mechanists believe that behavior is caused by either factors external to the individual (efficient causes) or those defining the individual's biological makeup (material causes). Efficient causes include such things as parenting style, educational opportunities, and peer group composition. Material causes include inherited genetic characteristics and more general biological qualities such as temperament or information processing capability.

Two prominent examples of work within a Mechanistic Worldview are the operant conditioning model, most closely associated with B. F. Skinner (1904-1990), and the behavior genetic model, associated with the work of Robert Plomin and Sandra Scarr, among others. These two models are very contradictory. Skinner's work reflects the nurture side of the nature-nurture debate, while Plomin and Scarr's work reflects the nature side of the debate.

Operant Conditioning Model

Skinner's operant conditioning model examines the relationship between a behavior and its consequence. As a model of human development, the operant model is seen as a means of understanding how life experiences influence an individual's actions. It demonstrates how changes in the consequences of one's behavior can in turn modify that behavior. In essence, responses are more likely to increase if followed by a positive (i.e., desirable) consequence and less likely if followed by a negative (i.e., undesirable) consequence. Skinner also found that the timing or schedule of the contingent reinforcement is an equally significant variable. Continuous reinforcement is generally seen as more effective in establishing a response; variable or intermittent reinforcement is seen as more effective at maintaining a response at a high level once it has been established.

Skinner restricted his actual work to laboratory animals—pigeons and mice in particular—but he made it clear in his writings that he saw these general principles as governing the behavior of all species, human or otherwise. Further, others working in this tradition have demonstrated that these principles of operant conditioning are very useful in helping to un-tangle complicated family dynamics as well as the more subtle forms of observational learning.

Behavior Genetic Model

Behavior genetic models offer a different approach to answering the perennial nature-nurture debate. Through elaborate statistical procedures, behavior geneticists attempt to determine how much of the difference in a group of individuals can be said to be due to genetic factors and how much to environmental factors. Behavior genetic research with humans cannot, of course, involve selective breeding (the preferred technique when working with animals), so behavior genetic researchers look for situations that they believe allow for "experiments in nature." The two most common research designs for humans involve comparing individuals of different degrees of genetic relatedness and comparing adopted children to both their biological and adopted parents. Behavior genetic researchers report that both types of studies show a significant genetic contribution to many human characteristics, including intelligence and personality. That is, identical twins appear more similar than fraternal twins or siblings, who are in turn more similar than cousins, who are in turn more similar than unrelated individuals. Further, adopted children share many characteristics with their biological parents, even if they are adopted at birth.

The Organismic Worldview

Those favoring an Organismic Worldview recognize both efficient and material causes as important but place even more emphasis on what they see as formal and final causes. Formal causes reflect the organizational quality of all living systems, while final causes reflect organicists' belief that human development is a directional process. To use an analogy, when hydrogen and oxygen are combined to form water, a substance is created with properties radically different than either of its two constituents. At room temperature, hydrogen and oxygen each exists as a gas but water exists asa liquid. Water is very good for putting out fires, while oxygen and hydrogen actually have the opposite effect. As such, the emerging properties of water are radically different from the properties of the individual elements of which it is comprised. In the same way, organicists argue that humans are each more than the sum of their parts and that humans are actively involved in their own construction.

Two of the major theoretical traditions within the Organismic Worldview are the psychoanalytic models associated with the work of Sigmund Freud (1856-1939) and Erik Erikson (1902-1994), and the cognitive developmental model associated with the work of Jean Piaget (1896-1980).

Freud's Psychoanalytic Model

Freud's work, although highly controversial both then and now, is important because it helps highlight the importance of the early bonds between a parent and a child and helps show how experiences early in life may influence subsequent life experiences.

It is ironic that Freud's theory, one of the most controversial theories of child development, is based not on a careful examination of children but rather on clinical interviews he conducted with adult patients in the course of his psychiatric practice in Vienna at the turn of the twentieth century. Freud, the clinician, believed that his adult patients' problems stemmed from their early childhood experiences, and as a result his approach to therapy was to help them regress to those early experiences so that the traumatic nature of the experiences could be uncovered and therefore resolved.

Freud saw activity during the first year of life, what he called the oral stage, centered on the mouth and the process of learning to take in, both in the biological and psychological sense, those things that initially are external to the infant. Because this taking in or incorporating is pleasurable to the child, Freud saw those associated with the process, most notable the mother and the father, as also acquiring positive value in the eyes of the infant. To Freud, a psychic force, the id, regulated these early efforts on the part of the infant. The id exists in the infant's subconscious and has the sole purpose of reducing tension and increasing gratification.

By age two or three, during the anal stage, the focus of activity shifts from the oral region to the anal region, with issues of retention and elimination, again, at both the biological and psychological levels, becoming paramount. Because the child is now being asked to learn to balance power and control, a second psychic force, the ego, emerges as a regulatory mechanism. Unlike the id, the ego resides partly in consciousness and partly in unconsciousness and as such serves to help the child become socialized; that is, it helps the child recognize that she must respond to considerations other than her own immediate gratification.

The preschool years witness the phallic stage and a further shift in focus to the genitalia and issues of sex role identification. Freud sees this process as one of conflict for the child because the child initially sees the same-sex parent as a competitor for the affections of the opposite-sex parent rather than as a mentor and role model. Successful resolution of the conflict comes about through the emergence of a third psychic force, the superego. The superego resides entirely in the child's consciousness and is, in essence, the child's conscience. It is the superego that helps the child recognize the legitimacy of society's social expectations for the child.

Middle childhood brings a respite to the child, a time Freud called the latency stage. According to Freud, from age five to thirteen children's efforts are directed at establishing same-sex friendships, strengthening ties with parents, and meeting the social and intellectual demands imposed by school and society.

The adolescent years witness the emergence of the genital stage. Again the focus is on the genitalia but it has shifted from parent-child issues to issues of establishing intimacy with a same-age peer. How successful the adolescent and young adult is in establishing adult sexual relationships is, to Freud, largely a function of how successfully earlier stages were resolved.

Erikson's Psychoanalytic Model

Erikson's revision of Freud's theory reflected his belief in the interpersonal nature of human development. Erikson offered a sequence of eight developmental stages—or as he called them, psychosocial tasks—that must be successfully accomplished for a person to become fully developed. Erikson's first psychosocial task involves developing a basic sense of trust and is seen as the major developmental milestone for the infant. Developing a basic sense of trust comes about through the interactions with the infant's primary caregivers. The more predictable and appropriate the interactions, the more easily a sense of trust is established.

Erikson's remaining seven psychosocial tasks then follow in sequence, each associated with a particular period of the lifespan. Toddlers are expected to use their sense of trust to venture forth and establish a basic sense of autonomy. The preschooler, in turn is asked to develop a sense of initiative. By middle childhood, this sense of initiative is now expected to more fully develop into a sense of industry. One characteristic of Erikson's work that is well illustrated in these first four stages is their nested nature. For successful completion, each requires resolution at all previous levels. No resolution halts development; partial resolution restricts further development.

By adolescence, individuals are asked to form a sense of identity, which is seen as forming the foundation for the establishment of a sense of intimacy, the defining event of the early years of adulthood. Intimacy typically leads to some form of permanent bond, which in turn often leads to parenthood and the opportunity to develop a sense of generativity, or concern for the next generation. Finally, toward the end of life, one is asked to form a sense of ego integrity, to accept the life you have led as the life you have led.

Piaget's Cognitive Development Model

Unlike Erikson who focused on interpersonal relationships, Piaget focused on children's cognitive development, in particular on the cognitive structures or mechanisms that are available to individuals of different ages to help them make meaning out of their everyday experiences. Piaget saw this effort to make meaning as reflecting a desire to maintain an equilibrium or balance between the individual and his context. New experiences create a degree of disequilibrium, which the individual tries to adapt to either by drawing on previous experiences to make sense of the new one (a process Piaget referred to as assimilation) or by making the necessary cognitive changes to adapt to the new situation (a process of accommodation). This continual process of assimilation and accommodation leads to the changes in the individual's cognitive organization that were of interest to Piaget.

Piaget saw this developmental process as occurring in a sequence of four periods or stages. The first, the sensory-motor period, typically occurs during the first two years or so of life. It is marked by Piaget's observation that infants are initially unable to act or behave on the basis of their mental representations (literally, re-presentations) of their experiences but rather act on the basis of their sensory and motor impressions of these experiences. To Piaget's infant, what something means is based on whatever sensory or motor interactions the infant is able to have with the object, person, or experience.

Gradually over the second and third years of life, young children begin to acquire the ability to act, in a very elementary fashion, on their mental representations of objects, people, and events. This preoperational period, which typically lasts until ages five to seven, is characterized by the child's growing use of language, the increasing ability to engage in pretend play and imitation, and a growing ability to understand simple functional relationships. These young children, however, still have difficulty in appreciating the fact that others do not see things from the same perspective as they do (what Piaget referred to as egocentric thought), and they are still relatively easily fooled by how things appear to be rather than how they must be.

As children enter middle childhood around age five to age seven, they move into the period of concrete operational thought. They are now no longer easily fooled by their perceptions because they have the cognitive skills necessary to have their logic "correct" their perception. Concrete operational children demonstrate the cognitive skills necessary to arrange, organize, and classify information; use the types of logical operations necessary for the understanding of mathematical and scientific operations; and modify their comments to reflect the perspective of the listener.

Beginning in adolescence and continuing throughout the adult years, formal operational adults are potentially able to apply logic to all situations— hypothetical or real. Piaget saw this ability to have "thought take flight" as a partial explanation for the expansiveness of adolescent behavior and even for the difficulty adolescents and young adults have in initially settling into productive adults lives.

The Contextualist Worldview

Although there are many differences between a mechanistic and an organismic worldview, they nevertheless share one important characteristic—they each view the process of development as universal. This emphasis on universality is one of the ways in which these two worldviews can be contrasted to the third, Contextualism. Contextualists do not believe that there are universal laws of development; rather, they argue that the forces that contribute to development are specific to historical time and social place.

Contextualists make their nonuniversal argument for two reasons: one empirical and one conceptual. From an empirical perspective, they argue that there is more than enough variability in the data comparing individuals and groups from different settings to raise serious questions about the assumption that human development reflects the same universal set of variables. From a conceptual perspective, contextualists argue that since it is impossible to ever have an objective (i.e., context-free) perspective on human development, then it is impossible to make judgments that are not culturally based.

Lev Vygotsky's (1896-1934) cultural-historical theory of human development is a good example of a theory rooted in a Contextualist Worldview since it places great emphasis on the role of culture in both defining and then transmitting the sign and symbol systems used in that culture. Sign and symbol systems are the ways cultures note and code information. They are reflected in the nature of the language, in ways for quantifying information, in the expression of the arts, and more generally in the ways people establish, maintain, and transmit social institutions and relationships across generations.

Vygotsky saw language as the defining characteristic of humans as a species, the one element that distinguishes humans from other species. Language allows for a shared communication, which in turn allows for collective effort or labor. This effort, in turn, sets the foundation for the progressive evolution of culture across generations. To Vygotsky, culture is a uniquely human phenomenon, allowing history to replace biology as the defining element in the lives of humans.

Of the various elements of Vygotsky's theory, the one that continues to receive the most attention, is his concept of the zone of proximal development (ZPD). Vygotsky saw the ZPD as the mechanism through which a culture's sign and symbol systems were passed from generation to generation; not surprisingly, many educators see it as the key element in the educational process of children. The ZPD represents an interval between what a child (or adult) is able to do alone and what that person can do with the support of a more skilled person. For activity in the ZPD to be educationally meaningful, the teacher must have a clear sense of both what the child should learn and the child's current interests and abilities. In essence, intersubjectivity needs to be established between teacher and child so that the learner understands the goals of the teacher, and the teacher understands the child's present level. A failure to establish intersubjectivity indicates that the teacher will be ineffective in helping the child acquire new information because the strategies the teacher uses to help support the child's learning will be ineffective or inappropriate.

In addition to highlighting the educational process, the ZPD also highlights another important element of Vygotsky's theory, namely, the notion that the intermental always precedes the intramental. By this Vygotsky meant that all knowledge is first acquired as social knowledge and only later is it internalized and comprehended by the child. It is because all knowledge is first transmitted as social knowledge that the cultural-historical context of a particular culture is so important in understanding and defining an individual's development.

People sometimes tend to think of theories as abstract and not useful, as something only academics argue or care about. Actually nothing could be further from the truth. Theory is the foundation upon which all everyday ideas about human behavior and development are based. In the words of psychologist Kurt Lewin (1890-1947), "there is nothing so useful as a good theory."

See also:DEVELOPMENTAL NORMS; ERIKSON, ERIK; FREUD, SIGMUND; MILESTONES OF DEVELOPMENT; PIAGET, JEAN; SKINNER, B. F.; VYGOTSKY, LEV

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Dale E.Goldhaber