Developmental Psychology

I. The FieldHarold W. Stevenson

BIBLIOGRAPHY

II. A Theory of DevelopmentJean Piaget

BIBLIOGRAPHY

I THE FIELD

Developmental psychology is concerned with the study of changes in behavior throughout the life span. Although, logically, equal emphasis should be placed on development during all stages of life, so far most research has dealt primarily with infants, children, and adolescents. Because of this emphasis the term “developmental psychology” is often used interchangeably with the older terms “child psychology,” “adolescent psychology,” and “genetic psychology.” These areas are distinct from one another, but it is impractical to discuss them separately. Child and adolescent psychology traditionally include the investigation of behavior at, rather than across, particular periods of development, and genetic psychology involves a concern for ontogenetic as well as phylogenetic changes in behavior. Underlying all the terms, however, is a concern with the emergence of behavior in the human being, and, therefore, in this discussion no attempt is made to distinguish between the various approaches [seeAdolescence; Aging; Infancy].

In the growth of developmental psychology theoretical positions, practical needs, public awareness, and support of research have been closely interrelated. In various phases different forces have been dominant, depending on the psychological and social milieu of the time. The field, therefore, has been one of shifting emphases. It is necessary to review the historical background of developmental psychology in order to understand its current structure.

The early period (1880–1920)

Although for centuries parents and other adults had observed children and gathered much “common-sense” knowledge about them, the information was contaminated by the biases of the parent–child relationship and the goals and wishes of other observers. Interest in systematically investigating developmental changes in behavior is, in fact, relatively recent. Research in this area received its initial impetus from the late nineteenth-century work in evolutionary biology. Charles Darwin, Wil-helm T. Preyer, and other biologists observed the development of human infants as a means of gaining further understanding of human evolution. After the publication of these observations, many baby biographies were published. They gave some indications of the changes that occur in the infant’s repertoire of behavior, although they were typically limited to a few cases and covered only a restricted age range.

The theory of evolution had a stimulating effect on other types of research, including that of the “founder” of developmental psychology, G. Stanley Hall. His belief in the theory that ontogeny recapitulates phylogeny resulted in his studying the behavior of the individual child as a source of in-sight into the behavior of man at earlier evolutionary periods. Many aspects of children’s behavior were observed, including play and social relationships.

Hall introduced the questionnaire method, marking the end of a period in which observation was the primary method of obtaining data; questionnaires came to be widely used for studies of children’s thoughts, interests, and wishes. Soon labora-tory procedures were applied to children, but the early experiments tended to be little more than demonstrations that certain phenomena associated with lower animals or with adults also occur in children. These studies dealt with the traditional topics of experimental psychology, such as memory, learning, sensation, and perception. In many cases, studies originally using animals or college students were adapted so that children could be used as subjects.

Intelligence testing

By 1890 there was considerable emphasis on objective observation and laboratory methods. Society was faced with the growing number of problems related to children that accompanied increased urbanization and expansion of public education. When, for example, the question of how to handle mental defectives in schools and institutions arose, groups of individuals in Great Britain and France began studies of how to assess and deal with such children. One of the most significant outcomes of these investigations was the development by Alfred Binet of a scale to distinguish between individuals of normal and subnormal intelligence. Whereas previous efforts to assess intelligence had been unsatisfactory, Binet’s work in constructing tests, which involved complex verbal and adaptive functions rather than simple sensory or motor functions, yielded a successful scale. It was soon obvious that such a scale had broader use than solely distinguishing between normal and defective children. Further work by Binet and others, such as Lewis M. Terman, resulted in useful tests for “measuring” children’s intelligence and investigating the effects of variables potentially capable of influencing intellectual development [see Intelligence and Intelligence Testing].

Psychoanalysis

During this period Sigmund Freud was developing a theory of psychic functioning that emphasized the importance of childhood experiences as determinants of later behavior. Aspects of the theory were presented in 1909 to developmental psychologists and others at Clark University. Although Freud directed attention toward the early emotional life of children, his work had a minimal effect on early research in developmental psychology. Not until the 1930s, when developmental psychologists were no longer so strongly influenced by biological thinking, did the resistance to his views decrease and did serious investigations of his ideas concerning the effects of early experiences on psychological development begin.

The period of expansion (1920–1940)

Research during the first two decades of the 1900s was aimed at providing a clearer delineation and categorization of children’s behavior. The research was highly empirical and not significantly influenced by theoretical analysis of psychological functioning. The work of this period, however, provided data necessary for the later development of systematic positions.

By the 1920s developmental psychology was rapidly becoming a visible and important area in psychology. The belief was widely held that the application of scientific methods to the study of children would lead to solutions of problems in education, pediatrics, child care, and treatment. Educators began lecturing parents on how to rear children. Clinics were organized to evaluate children’s abilities and to advise parents on such matters as discipline, toilet training, and feeding. Nursery schools were established in most large universities and in many colleges and were quickly put to use as a source of subjects for psychological research. Most important, funds became available for the support of research. The most notable donor was the Laura Spelman Rockefeller Fund, under whose auspices institutes devoted to research with normal children were established or extended at the universities of California, Iowa, Minnesota, and Toronto, and at Columbia University. The Fels Research Institute and the Yale Child Study Center also became leading centers for the study of children’s behavior in the United States. The Institut J.-J. Rousseau in Geneva and the Vienna Psychologische Institut were the most active European institutions for research in developmental psychology. The 1920s and 1930s were exciting and productive years at these institutes, but because the institutes were separated from departments of psychology, developmental psychologists tended to be isolated from psychologists interested in other aspects of behavior. Only during the past few years has the relationship with general psychology been firmly re-established.

Divergent viewpoints on how environmental and biological factors influence behavior resulted in a major controversy over the question of the contributions of nature and nurture to intellectual functioning. It was easy to take sides; it was much more difficult to accumulate information that withstood the tests of critical scrutiny. The controversy eventually ended in a stalemate, for although scores of studies were published, few survived the devastating attacks that were waged against their design, execution, and analysis. Solutions for the enormously complex issues that were being raised would have to await the time when developmental psychologists had more sophisticated tools and information at their disposal.

Behaviorism and its critics

The introduction of behaviorism into developmental psychology in the 1930s marked the beginning of an era in which schools of psychology, each with its own theories, problems, and preferred methods, polarized the field. Previous research had been aimed at providing information about children’s behavior; now research was often directed toward establishing the validity of theories advanced by various schools. Behaviorism had an effective and vigorous advocate in John B. Watson. Edward L. Thorndike and Ivan P. Pavlov had provided a background of information and techniques in their studies of learning and conditioning in animals, which Watson was able to use to develop his approach to psychology. He espoused an extreme form of environmentalism and relied heavily on the use of conditioning as the means for modifying behavior. His studies of infant behavior and of the acquisition and extinction of fear responses in children became classics, and his belief that introspection should be superseded by objective observation and measurement of behavior exerted a healthy influence on developmental psychology. It was not long, however, before advocates of other views responded critically to Watson’s position.

Among the most vocal schools of critics were gestalt psychologists and psychoanalysts. Although at the time neither group had a large influence on developmental psychology, their views provided the basis for later work. Another critic who took strong exception to the associationistic view of American behaviorists was Jean Piaget. As a result of his training in biology, Piaget emphasized the adaptive functions of behavior in maintaining an equilibrium between the individual and the environment. Piaget’s views were elaborated into a comprehensive theory of cognitive development. The contrast between him and the behaviorists extended to all aspects of their work. Whereas the behaviorists utilized the experimental method in their investigations of simple forms of behavior and emphasized the role of controlled experiences in the modification of behavior, Piaget preferred the clinical method and chose to study the interaction of maturation and experience in the production of complex behavior and higher thought processes.

Normative and longitudinal studies

The charting of the development of behavior was not confined to cognitive development. Arnold Gesell at Yale and Charlotte Bühler in Vienna had begun extensive normative studies of child development. For nearly forty years Gesell maintained an active program of research in the exploration of motor, adaptive, language, and personal–social behavior from birth through adolescence. The normative information from these studies, along with the results of his investigations of feeding, sleep, and other topics, became a major source of guidance for mothers in many countries. Gesell, like Piaget, had a strong biological orientation. While other American psychologists were proclaiming the influence of the environment on behavior, Gesell continued to show how specific types of experiences may have differential effects on behavior, depending on the maturational level of the individual.

A series of longitudinal studies of child development was initiated in the early 1930s. The longitudinal method had not been employed extensively prior to this time, although such investigations as Terman’s famous study of gifted individuals had demonstrated its productivity. At the University of California, Nancy Bayley began a study of the development of mental abilities in infants and children (1940), Herbert Stolz and Harold Jones began a study of somatic and psychological development during adolescence, and Jean Macfarlane began a study of personality development. At the Fels Research Institute, Lester Sontag and his associates began a comprehensive longitudinal study of growth and development. All these studies are still being conducted; data are being collected, and old data are being analyzed in new and interesting ways [see Personality, article onpersonality development; and Sensory and motor development].

Gestalt and field theories

Psychology began to be influenced significantly by the work of the gestalt psychologists, who, in turn, were influenced by field theory from physical science. The extension of the gestalt approach by Kurt Lewin had the greatest influence on research with children. During his years in Berlin and in the United States, Lewin directed a series of studies aimed at demonstrating the important role of situational factors in determining behavior. Lewin’s preference for an ahistorical approach to the analysis of behavior led him and others to a careful consideration of the structure of the psychological field and the forces operating in it. [SeeField theory; Gestalt theory; and the biography ofLewin.]

Later developments (1940–1965)

The remarkable rate of growth in developmental psychology was seriously curtailed at the end of the 1930s. Many factors contributed to a temporary decline in activity. The normative, descriptive approach had lost its allure; it was no longer of interest to reaffirm the fact that behavior developed systematically. Other areas of psychology appeared to be more challenging, and the number of persons entering developmental psychology decreased. World War ii disrupted research programs. Perhaps as important as any factor, however, was the withdrawal of supporting funds from the institutes and the general unavailability of new funds for research. For about fifteen years it became more and more difficult to initiate new research projects and, in many cases, to complete the analyses of data obtained from earlier studies. In 1938, for example, approximately 500 publications concerned with children’s behavior appeared; by 1949 the number had dropped to approximately 250. The general level of the work also began to decline; writings became more speculative and less dependent on original observations or experiments (see Barker 1951). Fortunately, the field did not disintegrate; there was enough activity at an appropriately high level to maintain the interest in research with children during the critical years.

The period of decline came to a halt in the mid-1950s, when interest in developmental psychology was reactivated. Since then, interest has increased at a rapid pace and there has been a revitalization of the area of study. Research with children has been greatly stimulated by the rapid and sophisticated advances in psychological theories, methodology, and instrumentation. Many of the theoretical positions in general psychology have direct relevance to the discussion of the emergence of behavior and are readily applicable to developmental investigations. Funds became available at an unprecedented level to support research and training. In the United States, for example, in 1962, a national Institute of Child Health and Human Development was established to provide leadership in training of investigators and research in developmental sciences, including developmental psychology. More powerful statistical analyses have been adopted and developed. Computers have made possible many types of studies that could never have been carried out without rapid mechanical analyses of the data.

The descriptive approach in developmental psychology has been replaced by a variable-oriented approach. The adoption of systematic positions dealing with developmental changes in children’s behavior has led to an increased interest in determining children’s responses to particular specifiable or manipulable variables and to a decreased interest in describing behavior in naturalistic or controlled settings. There is a tendency for subsystems to be developed that deal with specific aspects rather than with whole domains of behavior. The level of conceptualization has increased; concepts and processes now dominate thinking in developmental psychology.

There has been a redistribution of emphases among the various methods used in studying children. The experimental method has gained in popularity, primarily because of the opportunity it allows for the control of both independent and dependent variables. An experiment is no longer conceived merely as a controlled situation yielding quantitative data but as a method that permits the manipulation of the variables under study. Few long-term longitudinal studies have been initiated; the problems involved in the selecting of appropriate measures at the beginning of the study, the maintaining of the sample of subjects over long periods of time, and the organizing of the large amounts of data accumulated in such studies have discouraged most investigators from undertaking more than four-year or five-year longitudinal investigations. Observations, interviews, and tests tend to be used less frequently than they were in earlier periods, but they are still employed when they are particularly applicable to the topic under investigation,

Although attention continues to be directed toward developmental changes in such areas as children’s learning, motivation, perception, and language, new interests are developing. The rediscovery of Piaget’s work and modifications in behavior theory have resulted in a rapid development of interest in research in cognitive processes. Research in socialization has been stimulated by psychoanalytic and social learning theories. Studies of personality development have concentrated on specific aspects of behavior, for example, anxiety, aggression, and dependence, rather than attempting to deal with such global problems as adjustment and emotional behavior. Interest has been reawakened in the study of neonates, especially in their sensory, perceptual, and adaptive behavior. Cross-cultural studies, once in the domain of social anthropology, have been undertaken to ascertain the effects of different child-rearing practices on children’s later behavior. Studies of the ecology of behavior have resulted in detailed analyses of children’s behavior in naturalistic settings.

It is doubtful that twenty years ago anyone could have anticipated the remarkable resurgence of interest in developmental psychology that has occurred in the past decade. More research on basic processes of behavior is being conducted than in any previous period. Programs designed to train psychologists for research in developmental problems are being initiated and expanded, both in departments of psychology and in research institutes. A strong interest in applied problems is not evident, perhaps as a reaction to the overcommitment to the solution of social problems that characterized earlier work in developmental psychology. There are indications, however, that the techniques and knowledge now being accumulated can be used effectively in attacking the practical problems of the developing child. As the interest in such problems increases, it may be expected that the gap in communication between developmental psychology and pediatrics, education, sociology, and other disciplines will begin to close.

Harold W. Stevenson

[Directly related are the entriesAdolescence; Aging; Infancy; Sensory and motor development; Socialization. Other relevant material may be found inLearning, article onLearning in children; and in the biographies ofGesellandHall.]

BIBLIOGRAPHY

Advances in Child Development and Behavior. Vols. 1–2. Edited by Lewis P. Lipsitt and Charles C. Spiker. 1963–1965 New York: Academic Press.

Barker, Roger G. 1951 Child Psychology. Annual Review of Psychology 2:1–22.

Bayley, Nancy 1940 Studies in the Development of Young Children. Berkeley: Univ. of California Press.

Carmichael, Leonard (editor) (1946)1954 Manual of Child Psychology. 2d ed. New York: Wiley.

Hoffman, Martin L.; and Hoffman, Lois W. (editors) 1964 Review of Child Development Research. Vol. 1. New York: Russell Sage Foundation.

Kessen, William 1965 The Child. New York: Wiley.

Mussen, Paul H. (editor) 1960 Handbook of Research Methods in Child Development. New York: Wiley.

National Society for the Study of Education, Committee on Child Psychology 1963 Child Psychology. 62d Yearbook, part 1. Edited by Harold W. Stevenson. Univ. of Chicago Press.

II A THEORY OF DEVELOPMENT

Most theories of development and of intelligence seek to explain new problem-solving or concept-formation behavior by the influence of acquired experience, that is, as a function of external reinforcements; and they seek to explain the formation of logical structures by the influence of language. In this double perspective, knowledge tends to be considered as a kind of “copy” of reality: either as a sensorimotor copy, because the “associations” on which the learning is based are seen to be in one-toone correspondence with a series of relationships already existing in the external world, or as a verbal copy, because language simply describes a reality that is considered ready-made.

Without denying the fundamental importance of both acquired experience and language, I would include, in addition, the following three central notions:

(1) Knowledge of an object does not consist of having a static mental copy of the object but of effecting transformations on it and reaching some understanding of the mechanisms of these transformations. An intelligent act consists above all of coordinating operations, uniting, ordering (in the sense of introducing order), etc. These operations, which derive from the subject’s internalization of his own actions, are the instruments of the transformations that knowledge is concerned with.

(2) Logical relationships are, first and above all, operational structures. Although their most advanced forms are certainly expressed by language, their origins are found in the coordination of the subject’s own actions. Even at the sensorimotor, preverbal level, a child is involved in activities that include uniting, ordering, introducing correspondences, etc.; and these activities are the source of operations and logico-mathematical structures.

(3) Knowledge is not determined strictly by the knower, or by the objects known, but by exchanges or interactions between the knower and the objects (between the organism and the environment). The fundamental relation is not one of simple association but of assimilation and accommodation; the knower assimilates objects to the structures of his actions (or of his operations), and at the same time he accommodates these structures (by differentiating them) to the unforeseen aspects of the reality he encounters.

It is with this emphasis on the subject’s own activities and transformational operations that I look at the stages of mental development and the progressive formation of intelligence. In a word, a ready-made object knowledge is not assumed, because we must transform it in order to know it; nor is a fully formed knowing subject assumed, because the subject must elaborate his own structures through transforming objects.

Sensorimotor intelligence

Even at the sensorimotor level, before the emergence of language, we can see this two-sided development—the child’s thought structures develop in the very process of his “construction of reality.” Infants assimilate situations into their repertory of actions; they find out about new things by acting on them in the ways they are capable of, such as sucking and grasping. By repetition, coordination, and generalization, these actions engender a system of “schemas of assimilation.” For example, a child who already pulls things and places things comes to coordinate these actions in the form of pulling a little rug toward himself in order to reach something placed on it. On the other hand, as part of this same development, this intelligence structures reality. For instance, at first, objects have no permanence; the universe is one of moving tableaux that appear and disappear and are without spatial localization once they have disappeared. But with the coordination of actions, a “schema of the permanent object” develops: an object is sought after it has disappeared, and it thus continues to exist in the sense of its having a spatial localization even when it is actually outside the field of perception and action.

Another basic schema, which, at the practical level, is closely tied to the schema of the permanent object, is that of the coordination of positions and changes of position, what geometers term “the displacement group”—the coordination of movements from positions with the possibility of a return to the point of departure and of the use of detours or alternate routes to get to the same point. There is even a sensorimotor schema of causality. First, this consists of attributing phenomena to the subject’s own actions, without taking account of physical or spatial contact. Then, as causality is attributed to relations between objects themselves and some physical interaction is found necessary, there emerges progressive objectivation and spatialization of causal relations.

Sensorimotor intelligence thus makes two fundamental advances. (1) Actions are coordinated; and this is the source of later logic and operations, when these schemas will be internalized and restructured at the representational level. (2) From the point of view of structuring reality, the substructure is provided for certain fundamental concepts—object permanence, causality, space, and temporal succession. (For further elaboration on these ideas, see Piaget 1936; 1937.)

Figurative and operative symbolic functions

At about one and a half or two years of age, there emerge the beginnings of the symbolic function and representational evocation, or “thought” (or, again, internalized intelligence).

Knowing consists necessarily of a system of signification, and signification consists necessarily of a signifier and something signified. At the early sensorimotor level, the sensorimotor, perceptual, and postural actions upon objects—the schemas— are the things signified, and the signifiers are some aspect of these very schemas. Such signifiers are the cues or signals of conditioning, and at this early stage they are still relatively undifferentiated from what they signify.

By contrast, the symbolic function has its beginning (at around one and a half or two years) with the development of signifiers that are differentiated from the schemas that they signify; that is, some-thing can be evoked or represented by something other than a part of itself. Such signifiers may be symbols that bear some resemblance to what they stand for or signs that are arbitrary conventions.

Language and imitation

The words of a language are signs. In children, at the same time the language sign system appears other aspects of functioning, which are based on symbols rather than signs, emerge: deferred imitation, symbolic (or fictional) play, and mental imagery (which is internalized imitation). All of these are alternate ways of evoking situations and objects in their absence.

Imitation is the medium by which the child progresses from sensorimotor to representational functions. A form of imitation is already present at the sensorimotor stage. This is a material, or active, representation and takes place only in the presence of the model being imitated. It is non-deferred imitation (even though it may keep going for a while after the model has disappeared). It does not imply any form of mental representation, and it does not necessarily result in any. On the other hand, deferred imitation (imitation that starts in the absence of the model) does lead to representation, as is clear in the case of symbolic play. It then becomes internalized as a mental image, which permits the acquisition of language. (Language is based on this deferred imitation, not only on conditioning; otherwise it would develop much earlier.)

Thought is made possible by the emergence of the symbolic function, through the internalization of sensorimotor actions and through the reconstruction of the early structures on the level of representational signification. But before looking more closely at this reconstruction, we must introduce an essential, although often overlooked, distinction. The recent research of Piaget and Inhelder reveals this distinction more and more clearly.

Figurative and operative aspects of thought

At the heart of cognitive processes are two aspects— not separated sectors, but different poles: the figurative aspect and the operative aspect.

The figurative aspect deals with static configurations of reality and provides adequate figural representations of these states. This aspect is predominant in perception, in imitation, and in mental imagery that is a form of internalized imitation.

The operative aspect, on the other hand, deals with transformations of these states. This aspect is predominant in actions in general and, in the special case of operations, in internalized actions that have become reversible. The operations of adding and subtracting, for instance, are products of the actions of uniting and separating. The term “operative” refers to both actions and operations, while the term “operational” refers to operations alone.

This distinction between the figurative and the operative aspects is an important one from the point of view of the development of intelligence. In adults, the figurative is subordinated to the operative; that is, states are seen as the result of one transformation and the starting point for another. However, in young children, especially in children who have not yet begun to think operationally, these two aspects remain uncoordinated; the children are not capable of certain elementary forms of reasoning because they focus too much on fixed states, without seeking to relate them operationally. For instance, the majority of four- to six-year-olds think that after a liquid is poured from a wide glass into a narrow one there is more of it, because they note only the fixed levels of the liquid and not the pouring action, which links the initial and terminal states. (For further reference, see Piaget 1945; Piaget & Inhelder 1966.)

Preoperational thinking (two to seven years)

Operations are internalized, reversible actions, coordinated in total structures such as classifications, seriations, and multiplicative matrices. The psychological criterion for the existence of operational reversibility is the presence of the notion of conservation, a negative example of which is the children’s reactions to the liquids, cited above.

Sensorimotor intelligence manifests the threshold of operativity, since the displacement group itself is a total structure characterized by reversibility, and there is an invariant, or a conservation schema, in the form of the schema of the permanent object. But internalization is missing here. These schemas consist merely of physical, successive actions and not yet of simultaneous representations.

One would be tempted to think that as soon as the symbolic function was formed, these sensorimotor structures would be internalized as operational structures. This is indeed what finally takes place but, because it is much more difficult to reproduce an action in thought than to execute it physically, it takes place much more slowly than one might suppose. This internalization requires a total reconstruction on a new plane; and during the course of this construction, the child must go through the same difficulties he did on the sensori-motor level. For example, the four- to six-year-olds we studied knew perfectly well the route they took from home to school but could, nonetheless, not represent this route on a sand table.

Egocentrism and decentering

The necessary condition for operational development at this age is a decentering from the child’s own actions and own point of view. The phenomenon of the child’s centering on his own point of view and on his own actions is what is called egocentrism (a term that has often been misunderstood because of confusion with affective egocentrism). By egocentrism, I mean nothing more than the absence of cognitive decentering. Already at the sensorimotor level the course of development is one of progressive decentering from an initial state of radical egocentrism. The newborn infant has no awareness at all of his own identity, precisely because of the fact that he does not distinguish his own point of view from other possible points of view. As a result, he lives in a universe without objects, centered spatially, causally, and temporally on his own body. The construction of object permanence, the displacement group, and objective causality are characterized, in general, by progressive decentering, to the point where he becomes one element in a universe of objects and of spatial and causal coordinations. This Copernican revolution, as it were, must be effected all over again in the realm of representational thought and in social relations; another decentering is necessary to liberate the child from his own point of view. One example, from the realm of spatial representation, involves a three-dimensional model containing three mountains; the child is given a series of drawings made from various positions and is asked to indicate the angle from which each of the drawings was made. Children at the preoperational stage cannot do this. A social example is the question of the number of brothers in a family. A child will say, for instance, that he has two brothers but that each of them has only one brother—because he doesn’t count himself as a brother.

Absence of conservation in egocentrism. The main feature of egocentrism, however, is the absence of reversibility, and therefore of operations. None of the tests of conservation is successful at this level. We have already seen the example of the pouring of liquids. We get the same results using small beads instead of a liquid. Similarly, if ten blue tokens are lined up opposite a row of ten red tokens, the child will think that the number or quantity changes if you spread out or push together one of the rows. Again, if you give him two similar balls of Plasticine and then reshape one as a sausage or as a pancake, he will think that the quantity has changed. By about 7 or 8 years of age, he will affirm that the quantity has not been changed; but he will continue to think, until 9 or 10, that the weight has been changed; and only at 11 or 12 will he believe that the volume, as measured by water displacement, remains unchanged. These experiments, which were first conducted in Switzerland, have been replicated in other countries (for example, in the United States by Elkind 1961) with the same results.

In spatial conception at this age level, there is nonconservation of length. Two sticks of equal length will be judged equal by the child if they are placed side by side with their extremities aligned, but if one is moved so that it extends beyond the other, the child will now say that it is longer. Similarly, there is nonconservation of distance: the space between two points is considered smaller if an object is placed in the middle of it—empty space is not equated with filled space. Similarly, there is nonconservation of surfaces, volumes, etc. (For further reference, see Piaget & Inhelder 1941; 1948.)

The concrete operations

At seven or eight years of age, the first operational structures take form. These first operations are limited, dealing with manipulations of objects themselves and not with verbal hypotheses. They are limited to classes, relations, and number, dealing either with discontinuous elements or with spatial and temporal continuums. They do not attain the general level of propositional logic.

Moreover, these concrete operations do not cover the entire logic of classes and relations but only certain of the structures involved. These first operational structures, to which we have given the name of “groupings,” relate to contiguous inclusions and relationships, without yet being generally combinatorial. They are only semilattices and incomplete groups, like seriations, classifications, multiplicative matrices, etc.

Seriation

Seriation, or succession of transitive asymmetrical relations, has its roots in early preoperational, even sensorimotor, schemas. Very young children can arrange a series of blocks in the order of their size. But at this level, it is done only by successive trial and error, with no use of deductive transitivity (knowing that A > B and B > C means that A > C). At seven or eight, there is a systematic method, consisting of finding the smallest of all, then the smallest of the remaining ones, etc., so that each element is understood as being bigger than all the preceding ones and smaller than all the following ones. This is the basis for an immediate deductive understanding of transitivity.

Classifications

Classifications, too, are present at the preoperational level, but in a form that remains elementary because it lacks operational reversibility. When small children, say four-year-olds, are asked to make classifications of objects, they make “figural collections,” with them; that is, the spatial arrangement is made as if the class itself was dependent on a configuration in space. Slightly older children make nonfigural collections. The collections no longer have a significant shape, but they are still only material collections and not logical classes, because the children do not understand the intensive quantification of class inclusions. Suppose, for example, that we present seven primroses (class A) and three other flowers (class A’), which together make up a collection of ten flowers (class B = A + A’). The child will agree that all the primroses are flowers and that all the flowers are not primroses, but he does not conclude that there are fewer primroses than there are total flowers (A > B). He will say there are more primroses because there are only three others. He cannot reason at the same time with both the whole class and a subclass. In trying to compare A with B, he must split B into A and A’, and then since A is already one term of the comparison, the child uses A’ as the other term. At an advanced operational level, however, he will understand that A B – A’ and A’ = B – A. Therefore A > (A + A’), or A > B. In other words, understanding class inclusion presupposes operational reversibility.

The same sort of analysis can be made of children’s notions of correspondences, multiplicative matrices, etc. However, the operational mechanisms involved in the construction of the notion of whole numbers deserve special attention. We have already seen that even though children may use number names, it is not until the age of seven, on the average, that they are convinced of the conservation of number if the spatial arrangement is changed. The operational concept of number is a synthesis of class inclusion and ordering. On the one hand, there are the inclusions I > (I + I) > (I+ I- I). On the other, since all the elements are equivalent, with all qualitative differences having been abstracted, the only way to distinguish one element, I, from another is by introducing order. This order may be a spatial array, a temporal array, or a logical enumerating order of the type I → I → I, where the sign → indicates any sort of transitive order. Bertrand Russell maintained that the cardinal number was based on one-to-one correspondence between classes of the same extension, without having to introduce order, whereas the ordinal number was based uniquely on ordering. But the one-to-one correspondence to which he referred is not the qualitative correspondence of the logic of classes, such as is found in multiplicative matrices, for example, where an element corresponds to another because of corresponding properties, but is rather a correspondence of one unity to another unity, with the qualities abstracted. And this already presupposes an arithmetical unity, that is, number. Cardinal and ordinal numbers can be neither understood nor formalized independently of one another. Only by seeing number as a synthesis of inclusion and seriation can we avoid the vicious circle inherent in Russell’s formalization. This interpretation of number, as a synthesis of inclusion and seriation, was discovered purely through psychology and has since then been formalized by the logician J. B. Grize.

There is another whole area of operations at this level. So far, we have been discussing discontinuous elements, where the operations deal with likenesses and differences. There is also the area of infralogical or spatiotemporal operations, which deal with proximity and separation in a continuum.

Representative space

Representative space (as opposed to sensorimotor and perceptual space) is based on the following operations: partition and addition of parts (corresponding to addition of classes), placement and displacement (corresponding to seriation), and measuring as a synthesis of partition and displacement (as number is a synthesis of inclusion and seriation). There is a point of interest here from the point of view of philosophy of science. These spatial operations apply equally to Euclidean (metric) projective, and topo-logical space. In the historical development, Euclidean geometry is considered to have come first, followed much later by projective, and later still by topological, considerations. The psychological construction presented here is the contrary of this; topology is the most fundamental, with the other two being derived from it. We have found that in children, development follows this order. The first intuitions are topological, and from this come projective and Euclidean, or metric, representations.

Time

The operations involved in the notion of time are again similar. There is the ordering of successive events; there is inclusion of time intervals; and the synthesis of these leads to time measurement. The notion of time is based on a primitive intuition of speed, which determines judgments of speed much before there is any metric notion of speed as a ratio of space to time. (Speed as a prerequisite to understanding time, rather than vice versa, is closer to relativity physics than to classical physics.) This primitive notion of speed is ordinal, based simply on the intuition that if one moving thing overtakes another on the same path, it is going faster. This judgment of speed is based on spatial order (behind and ahead) and temporal order (before and after) but does not require any evaluation of length of time or size of interval. [For further reference, see Piaget 1946a; 1946b; Piaget & Szeminska 1941; Piaget, Inhelder, & Szeminska 1948; see alsoTime, article on Psychological aspects.]

Formal, or hypothetico-deductive, operations

The period of formal, or hypothetico-deductive, operations begins at about 11 or 12 years of age. Children start to be able to reason not only about concrete objects but about verbal hypotheses. The operations of propositional logic, in a natural, non-axiomatized form, of course, are added to the operational structures.

There are at least three types of external evidence of this new development. (1) Children are able to reason with verbal material alone, that is, without concrete referents. (2) In experimental problems they are able to make hypotheses about the possible factors and vary them systematically to test the hypotheses. (3) In general terms, they are now capable of “reflection,” that is, of thinking about thinking or of operations on operations. Propositional logic is a kind of system of operations raised to the second power, since the contents of the propositions are class or relational operations and since new operations are involved in the inter-propositional structure (implications, disjunction, etc.). This is why adolescents can construct theories, naive though they may be, whereas children cannot.

These operations have two main characteristics. First of all, they are combinatorial, giving rise, for example, to a more complex lattice structure in place of the simpler “groupings.” Second, the two forms of reversibility found at the concrete operational level are united in a single system known as the group of four transformations. These two types of reversibility are inversion, or negation (N), which characterizes classification structures, and reciprocity (R), which characterizes relational structures. The operations involved in the groups of four transformations then are N, R, I (identity), and C (correlativity); so that NR = C, NC = R, NRC = N, and NRC = I. With these operations, 11-and 12-year-olds can develop new operational schemas, such as proportions, double reference systems, etc. (see Inhelder & Piaget 1955).

The mechanism of intellectual development

The classical factors that usually are called upon to account for intellectual development are biological maturation, environmental influence (experience), and social transmission (education). Each of the three does play an important role, but they are insufficient to completely account for intellectual development. Thus a fourth is necessary.

Biological maturation clearly needs to be supplemented when we see that the speed of development of operational structures is dependent upon cultural settings, individual experience, etc.

As for experience as a unique explanatory factor, it is indeed true that all notions need a basis in experience, even logical and mathematical notions. But there are two distinctly different types of experience, although they often go together. Physical experience consists of acting upon objects and drawing some knowledge about the objects themselves, for example, weighing things and finding out that weight is not always proportional to volume. In logico-mathematical experience, on the other hand, the knowledge is drawn not from the objects that are acted upon but from the actions themselves. Arranging objects in various ways and finding out that the arrangement has no effect on the total number of objects is an example of this second type of experience. Physical experience certainly does not suffice to explain the development of intelligence. As for logico-mathematical experience, this is only a preparation for deductive thinking, which is based on the coordination of actions.

Finally, linguistic, educative, or social transmission, important though they are, can have an influence only to the extent that the child can assimilate what is offered to him into his own operational structures.

Progressive equilibration

Another factor thus becomes necessary—the progressive equilibration of actions as they become coordinated. There are two reasons why equilibrium is a satisfactory explanatory model. First, intellectual equilibrium derives from the subject’s activities as they compensate for external disturbances. Since compensation leads to reversibility, this progressive equilibration of the operational structures takes the form of progress toward ever-increasing reversibility. Equilibration can thus be seen as a possible definition of intelligence, as well as an interpretation of its development. Second, an operational structure is equilibrated once it has achieved reversibility, but before then it passes through preoperational steps of successive equilibration. If we follow this progressive equilibration, we see that any given step, although not necessarily the most probable at the outset, becomes the most probable, once the preceding step has been reached. Equilibration thus includes a model of successive probabilities that is capable of dealing with factual detail, and which thus provides a learning theory based on internal reinforcement and not only on external or empirical reinforcement (see Apostel, Mandelbrot, & Piaget 1957).

Perception and mental imagery

The research on intellectual development is only a part of this line of developmental research. There is also work in the fields of perception and mental imagery.

Perceptual development

In the area of perceptual development, two groups of phenomena have been identified: (1) effects that diminish in intensity but whose structure remains unchanged and (2) activities that become more articulated with age.

The effects that are not structurally modified but whose intensity decreases with age can be interpreted by a common probabilistic model. About 15 classic opticogeometric illusions have been studied developmentally. Examples of these are the Delboeuf illusion, the Müller–Lyer illusion, and illusions of angles, rectangles, parallelograms, etc. Each one was studied in a variety of different proportions; and at every age, positive and negative maxima were established for the proportions. The maxima proportions were found to be the same for every illusion, which permitted the effects of all of the illusions to be reduced to a general law, that of a “centration” effect: the areas focused on are overestimated, and the peripheral areas are underestimated. A study of ocular movement, by Piaget, Vinh-Bang, and Matalon (1958), was able to support this interpretation in some of the simpler situations. For instance, vertical lines are overestimated in comparison with horizontal lines, and subjects were in fact found to focus during much of the exposure on the summit of the vertical line. [SeePerception, article onillusions and aftereffects; Vision, article oneye movements.]

This centration effect was itself reduced to a probabilistic explanation based in part on the distribution of the points of “encounters” between elements of the figure and elements of the receptor organs and in part on the series of correspondences, or “couplings,” established among these points of encounter. Studies were carried out to establish temporal maxima for each of the illusions, in both children and adults, for exposures ranging from .01 second to 1.0 second. These studies confirmed the duality of these two factors.

The second group of phenomena—activities that become more articulate with age—stems from exploration activities, such as comparing parts of the figure, structuring the figure by introducing perceptual coordinates, anticipating parts of the figure, etc. These activities give rise to certain systematic secondary illusions by exaggerating the deformation resulting from systematic centration. Once again, eye movement studies have confirmed this interpretation, showing, among other things, how much more systematic adult perceptual exploration is than that of children. This explains why these illusions become more pronounced with age.

These perceptual activities, then, come more and more under the influence and direction of intelligence. Intelligence has no effect on the primary perceptual illusions, but it does have an effect on perceptual activity, guiding exploration and introducing its own structure. It is important to note to what extent a figurative function like perception lacks independent development and to what extent it is subordinated to operative functions. It has its beginnings in early motor behavior, and its later development is directed by operational intelligence.

Mental imagery

Another figurative function whose development has been systematically studied is mental imagery, which has been relatively neglected in recent years but, indeed, was never much studied in children. Once again there are two problems to study: (1) to establish whether the evolution of imagery is autonomous or whether it is influenced by operational development and (2) to establish whether imagery paves the way for operations or whether, on the contrary, it is modified and structured by the operations.

As far as the first problem is concerned, two principal types of imagery have been distinguished. Besides reproductive, or “copying,” imagery there is anticipatory imagery (which may be as simple as imagining the rotation of a stick as it pivots about one of its extremities). In children who are too young to engage in operations, reproductive imagery is adequate, but anticipatory imagery is far from adequate. The errors made are, in fact, reminiscent of the errors in preoperational thought. Anticipatory imagery does not, then, derive directly from reproductive imagery but depends on the intervention of operations. At the operational level, this imagery becomes more flexible and can serve as a useful symbolic auxiliary for operational thought.

The second problem is examined by going back to the various operational tests (conservation, for example) and having the children anticipate how the situation will be, after telling them what transformation is about to be carried out. For instance, for the conservation of number, 12 blue tokens are placed in a row 15–20 centimeters long. About 30 centimeters away, 12 red tokens are spread out in a row 30–40 centimeters long. Each blue token is coupled with a red token by means of a channel with walls 1 centimeter high, so that the tokens can move toward each other only along the channel and must ultimately meet. The children are asked, with the tokens in their original positions, whether there are as many blue as red, whether there will be as many if the blues are all moved up to where the reds are, whether there will be as many if they are moved up only halfway, etc. The findings are that small children are perfectly able to represent the displacement of the tokens, but before six and a half or seven years of age this does not lead them to assert that the number is the same. They report that the number increases as the row becomes longer, and decreases when the row is shorter. The anticipation remains transversal, focused on the length of the row. Later, at the operational level, it becomes longitudinal, focused on the paths traveled, and serves to verify the one-to-one correspondence. Other experiments support the same conclusion, namely, that adequate imagery in itself is not sufficient to bring about operational thinking but is structured and modified by the subject’s operational level (see Piaget 1961).

Epistemological conclusion

This entire body of research bears witness to a single broad intention: to put to experimental test the principal epistemological hypotheses about the nature of empirical and logico-mathematical knowledge.

Above all, it reveals the insufficiency of empiricism as an epistemological theory: the development of empirical knowledge itself does not demand an empiricist interpretation. In point of fact, the study of this development in children reveals that experience is never simply “read,” or passively registered. It is always assimilated by the subject into his own structured schemas. In other words, even physical knowledge (in its broadest sense) is always relative to a logico-mathematical framework brought to an experience by the subject himself. As for this framework, it is not simply a linguistic expression but is derived from the most general system of coordinations of the subject’s own actions. In short, it is operational.

However, to say that the subject plays an active role in structuring the physical objects of knowledge does not mean that knowledge is rooted in the subject alone, as the a priori epistemological theories maintain. (The a priori influence is still alive in some forms of gestalt theory.) Knowledge derives neither from objects independent of a subject nor from a subject independent of objects; it derives from an indissociable interaction between subject and object or, in more general terms, between organism and environment. This interaction leads at first to a lack of differentiation, or confusion, between objective and subjective, as is evident in the child’s egocentrism. Later, it takes two related developments. One is decentering, which results in the objectivity of experimental knowledge. (This objectivity is not a given of the knowing process but is a slow and laborious conquest.) The other is reflective abstraction, which leads to the construction of logico-mathematical structures. (See Piaget 1950.)

Jean Piaget

[Other relevant viaterial may be found inConcept formation; Infancy; Learning, especially articles OnDiscrimination learningandlearning in children; Perception, article Onperceptual development; Problem solving; Reasoning and logic; Thinking.]

BIBLIOGRAPHY

Apostel, LÉo; Mandelbrot, B.; and Piaget, J. 1957 Logique et équilibre. Paris: Presses Universitaires de France. → See especially Jean Piaget’s contribution.

Elkind, David 1961 Children’s Discovery of the Conservation of Mass, Weight and Volume: Piaget Replication Study II. Journal of Genetic Psychology 98: 219–227.

Inhelder, BÄrbel; and Piaget, Jean (1955) 1958 The Growth of Logical Thinking From Childhood to Adolescence. New York: Basic Books. → First published as De la logique de I’enfant à la logique de l’adolescent.

Piaget, Jean (1936) 1952 The Origins of Intelligence in Children. New York: International Universities Press. → First published in French.

Piaget, Jean (1937) 1954 The Construction of Reality in the Child. New York: Basic Books. → First published in French. Also published by Routledge in 1955 as the The Child’s Construction of Reality.

Piaget, Jean (1945) 1951 Play, Dreams, and Imitation in Childhood. New York: Norton; London: Heinemann. → First published in French.

Piaget, JEAN 1946a Les notions de mouvement et de vitesse chez l’enfant. Paris: Presses Universitaires de France.

Piaget, Jean 1946b Le développement de la notion du temps chez l’enfant. Paris: Presses Universitaires de France.

Piaget, Jean 1950 Introduction à l’épistemologie génétique. 3 vols. Paris: Presses Universitaires de France.

Piaget, Jean 1961 Les mécanismes perceptifs: Modèles probabilistes, analyse génétique, relations avec l’intelligence. Paris. Presses Universitaires de France.

Piaget, Jean; and Inhelder, Barbel 1941 Le développement des quantités chez l’enfant, Paris: Delachaux & Niestlé.

Piaget, Jean; and Inhelder, BÄrbel (1948) 1956 The Child’s Conception of Space. London: Routledge. → First published in French.

Piaget, Jean; and Inhelder, BÄrbel 1966 L’image mentale chez l’enfant. Paris: Presses Universitaires de France.

Piaget, Jean; Inhelder, B.; and Szeminska, A. (1948) 1960 The Child’s Conception of Geometry. New York: Basic Books. → First published in French.

Piaget, Jean; and Szeminska, Alina (1941) 1952 The Child’s Conception of Number. London: Routledge. → First published in French.

Piaget, Jean; Vinh-Bang; and Matalon, B. 1958 Note on the Law of the Temporal Maximum of Some Optico-Geometric Illusions. American Journal of Psychology 71:277–282.

Developmental Psychology

THEORETICAL FRAMEWORKS

INVESTIGATIVE METHODS

BIBLIOGRAPHY

Developmental psychology is the branch of psychology dedicated to identifying and explaining the continuities and changes that individuals display over their lifetimes. In particular developmental psychologists seek to understand the mechanisms or factors that are deemed responsible for the immense changes that occur in human thought, behavior, biology, and emotion from the very beginning of life through to the end—from “womb to tomb” (Shaffer, Wood, and Willoughby 2002).

Historically, early theories of development focused on trying to explain the development that occurs primarily during the first decade of life, with a focus on infancy and early child development. Scant attention was paid to the development that occurs during adolescence and on into adulthood. Societal changes that occurred during the 1950s and 1960s, however, led to a critical shift in theories and research in the field of developmental psychology. With respect to adolescence, for instance, the youth movements of the 1960s brought a new interest in understanding the teenage years and led to a marked theoretical alteration in the understanding of adolescence. Before then little attention had been paid to the empirical investigation of adolescents, and the extant theories of adolescence, primarily based on clinical experiences and anecdotal reports, portrayed the teen years as a time of “storm and stress”—a time during which individuals experience severe emotional turmoil and disturbance (e.g., Hall 1904). But data collected from adolescents themselves revealed that the teen years were not as tumultuous as previously assumed and that in fact the majority of adolescents (80%) reported traversing the teen years with little turmoil, relating well to their families and peers, and being comfortable with their social and cultural values (Offer and Schonert-Reichl 1992).

THEORETICAL FRAMEWORKS

Early twenty-first century views of development examine development across the life span: the prenatal period, infancy and toddlerhood, the preschool period, middle childhood, adolescence, young adulthood, middle adulthood, and late adulthood. A life span approach to development encompasses the scientific study of human growth, change, and stability (Feldman 2006). Researchers with this perspective seek to unravel universal principles of development, characteristics, and traits that differentiate people from one another, with a focus on physical, cognitive, personality, and social development. Demographic changes since the 1980s have spurred a new conception of development for the period identified as “emerging adulthood,” which spans the ages eighteen to twenty-five (Arnett 2000).

In contrast to the life span development approach, another theoretical framework for understanding development over time is the life course perspective. Life course theory emerged in the 1960s from the need to understand how individual lives are socially patterned over time and to examine the processes by which lives are changed by changing environments in which time, context, and process are an explicit part of the analysis. More specifically, life course researchers take into account both stability and change in lives as they unfold across time and generations and in historical, social, and cultural contexts.

The life course approach is an increasingly influential paradigm in social scientific thinking. In the words of Anne Colby, this theoretical approach represents “one of the most important achievements of social science in the second half of the 20th century” (Colby 1998, p. viii). One of the pioneers in this field is Glen Elder Jr., who studied children of the Great Depression, emphasizing how individual lives are socially patterned over time and the processes by which lives are changed by changing environments (Elder and Shanahan 2006).

The science of developmental psychology lacks a comprehensive and widely accepted developmental theory that unifies the field (Cole, Cole, and Lightfoot 2005). Instead, many different theories have been proposed in the study of development, demonstrating how different theories lead to different explanations of behavior across the life span. The most influential and enduring theoretical frameworks have included the psychoanalytic, learning, cognitive-developmental, and ecological systems viewpoints. Sigmund Freud was among the first to emphasize the centrality of emotional life to the formation and function of personality development (Cole, Cole, and Lightfoot 2005). His psychoanalytic theory was rooted in the idea that development moves through a series of stages in which individuals confront conflicts between their biological drives and their social expectations. Freud envisioned the immense power of the unconscious as a determinant of behavior and argued that development is largely molded by experiences in the first years of life. Although psychoanalytic theory has profoundly influenced psychology, among other fields, it is subject to criticism. Even among his own circle of disciples, Freud’s theories did not go unchallenged (Passer, Smith, Atkinson, et al. 2005). Although neoanalytic contemporaries of Freud, such as Alfred Adler, Karen Horney, Erik Erikson, and Carl Jung, agreed on the importance of both the unconscious and of childhood experiences, most argued that Freud did not give social and cultural factors sufficient importance in the role of development. Indeed because of the many criticisms leveled at Freud’s theories in terms of generalizabilty and testability, few present-day developmentalists are strong supporters of Freud’s theories (Shaffer, Wood, and Willoughby 2002).

In contrast to psychoanalytic theories, learning theories emphasize that development occurs as a result of behaviors learned through associations with different kinds of consequences. The most influential proponents of this perspective, John B. Watson and B. F. Skinner, argued that individuals tend to repeat behaviors that have resulted in rewards or that have allowed them to avoid unpleasant consequences. Social learning theorists such as Albert Bandura expanded upon traditional learning views to consider that a great deal of learning develops through the observation of others in the social context. Through a process known as modeling, children come to imitate behaviors they have seen others do, especially if they observe such behaviors to have positive consequences (DeHart, Sroufe, and Cooper 2004). Perhaps the greatest contribution of the learning viewpoint to understanding development has been the wealth of information gleaned through tightly controlled experiments. Learning theories are precise and testable and have helped developmentalists begin to understand why and how people form emotional attachments, adopt gender roles, make friends, and learn to abide by laws and rules (Shaffer, Wood, and Willoughby 2002). Nonetheless, the learning approach is a grossly oversimplified account of human development; it tends to overlook the contexts in which development occurs and often fails to recognize the cognitively active role that individuals play in their own development.

The cognitive-developmental perspective addresses some of these criticisms by focusing on the view that individuals actively construct a system for understanding the world rather than passively acquiring new information through simple learning mechanisms. Cognitive develop-mentalists seek to understand and explain the normative development of reasoning and thinking skills and argue that such skills progress through a universal sequence of invariant and qualitatively different stages. Jean Piaget is the most prominent developmental psychologist of the twentieth century, having contributed more to our understanding of cognitive development than any other scholar (Shaffer, Wood, and Willoughby 2002). Piaget’s theories legitimized the study of children’s thinking, linked moral development to cognitive development, and contributed to developmental research in social cognition—the kind of thinking that people display about the thoughts, feelings, motives, and behaviors of themselves and other people (Shaffer, Wood, and Willoughby 2002). Although critics have challenged the sequence of Piaget’s stages and recognize that he underestimated the ages at which cognitive skills develop, it is almost impossible to exaggerate the impact that Piaget’s thinking has had on developmental psychology (Beilin 1994).

A final theoretical framework is ecological systems theory, posited by Urie Bronfrennbrenner (1979). This perspective begins by assuming that natural environments are the major source of influence on developing persons (Shaffer, Wood, and Willoughby 2002). The ecological framework views individuals in the context of all the various settings they inhabit on a daily bases (microsystems). These settings are related to one another in a variety of ways (mesosystems), which are in turn linked to settings and social institutions where an individual is not immediately present but which have an important influence on his or her development (exosystems). All of these systems are organized in terms of the culture’s dominant beliefs and ideologies (the macrosystem). Although the ecological systems perspective has gifted developmental psychology with an understanding of the complexities of the natural environment, the theory fails to explain how individuals process and learn from environmental information and is therefore not a complete account of how humans develop (Shaffer, Wood, and Willoughby 2002).

INVESTIGATIVE METHODS

Without a unified theory, how do developmental psychologists know anything about human development? Since the 1990s a variety of methods has been refined for gathering information about how development occurs (Cole, Cole, and Lightfoot 2005). Among the most widely used are naturalistic observations, survey research, and research experiments. However, no single method can answer every question about human development; each approach has its own strengths and limitations. Various approaches have a strategic role to play, dependent upon the topic under investigation and the answers being sought.

The most direct way to gather information about how development occurs is through naturalistic observation. By definition, naturalistic observation involves observing and recording behavior in naturally occurring situations without trying to manipulate the environment. Naturalistic observations allow developmentalists to observe how individuals behave in everyday life. However, such an approach is not without its limitations. For example, when people know they are being watched, they often behave differently than they normally would. In addition researchers often enter observational settings with expectations about what they are going to see and inevitably observe selectively in accordance with those expectations. Nonetheless, observational methods are a keystone of developmental research and a critical source of data about development (Cole, Cole, and Lightfoot 2005).

Researchers who opt for survey methods utilize structured questionnaire or interview techniques to ask participants questions related to such aspects of development as perceptions, feelings, or beliefs. Despite obvious shortcomings, such as attempts by respondents to present themselves in socially desirable ways, survey research is an excellent method for obtaining large amounts of information, often from a large number of participants, in relatively short periods of time.

A final investigative approach is the psychology experiment. In a true experiment the researcher controls conditions and systematically manipulates one or more variables so as to rule out all other influences on development except the one being investigated. The clear strength of the experimental method is its unique ability to isolate causal factors. That is, by controlling extraneous variables that may be influencing development, researchers can be confident that the variable of interest does indeed have an effect. A major drawback to experimental research is that the findings are not always generalizable to everyday settings, given that people do not always respond in the laboratory the way they do in the natural environment. Thus, as with the myriad of theories utilized to explain development, there are numerous approaches for investigation in the field of developmental psychology.

SEE ALSO Adolescent Psychology; Behaviorism; Child Development; Cognition; Erikson, Erik; Experiments; Freud, Sigmund; Gerontology; Jung, Carl; Maturation; Methodology; Piaget, Jean; Psychology; Skinner, B. F.; Stages of Development; Survey

BIBLIOGRAPHY

Arnett, Jeffrey Jensen. 2000. Emerging Adulthood: A Theory of Development from the Late Teens through the Twenties. American Psychologist 55: 469–480.

Beilin, Harry. 1994. Jean Piaget’s Enduring Contribution to Developmental Psychology. In A Century of Developmental Psychology, eds. Ross D. Parke, Peter A. Ornstein, John J. Reiser, and Carolyn Zahn-Waxler, 257–290. Washington, DC: American Psychological Association.

Bronfrennbrenner, Urie. 1979. The Ecology of Human Development. Cambridge, MA: Harvard University Press.

Colby, Anne. 1998. Forward: Crafting Life Course Studies. In Methods of Life Course Research: Qualitative and Quantitative Approaches, eds. Janet Z. Giele and Glen H. Elder Jr., viii. Thousand Oaks, CA: Sage.

Cole, Michael, Sheila R. Cole, and Cynthia Lightfoot. 2005. The Development of Children. 5th ed. New York: Worth.

DeHart, Gabie B., L. Alan Sroufe, and Robert G. Cooper. 2004. Child Development: Its Nature and Course. 5th ed. New York: McGraw Hill.

Elder, Glen H., Jr., and Michael J. Shanahan. 2006. The Life Course and Human Development. In Theoretical Models of Human Development, ed. Richard E. Lerner, 665–715. Vol. 1 of The Handbook of Child Psychology. 6th ed. New York: Wiley.

Feldman, Robert S. 2006. Development across the Life Span. 4th ed. Englewood Cliffs, NJ: Prentice Hall.

Hall, G. Stanley. 1904. Adolescence: Its Psychology and Its Relation to Physiology, Anthropology, Sociology, Sex, Crime, Religion, and Education. New York: D. Appleton.

Offer, Daniel, and Kimberly A. Schonert-Reichl. 1992. Debunking the Myths of Adolescence: Findings from Recent Research. Journal of the American Academy of Child and Adolescent Psychiatry 31: 1003–1014.

Passer, Michael W., Ronald E. Smith, Michael L. Atkinson, et al. 2005. Psychology: Frontiers and Applications. 2nd Canadian ed. Toronto: McGraw-Hill.

Shaffer, David R., Eileen Wood, and Teena Willoughby. 2002. Developmental Psychology: Childhood and Adolescence. 1st Canadian ed. Scarborough, ON: Thomson Nelson.

Cory L. Pedersen

Kimberly A. Schonert-Reichl

DEVELOPMENTAL PSYCHOLOGY

Developmental psychologists are interested in time- and age-related changes in cognitive and intellectual functioning, personality, and social relationships from birth to death. Theory and research deal with three core phenomena: general principles of developmental change, individual differences in development, and intervention possibilities. Two research designs are used to examine these phenomena: cross-sectional and longitudinal studies. Consider, for example, the study of intelligence across the life span. In order to determine general principles of age-related change in intelligence, a cross-sectional design that compares the performance of various age groups (e.g., children, adolescents, young and older adults) on the same test could be used. If children and older adults show a lower test performance compared with the other age groups, one could infer that intelligence increases with age in early life and declines in old age. However, other factors, such as historical changes in education, could also explain the low performance of older adults. Age group differences observed in cross-sectional studies are confounded with cohort differences in life experience and life contexts. Longitudinal studies in which the same individuals are repeatedly measured over time on the same test provide the best assessment of how performance changes with age.

Both cross-sectional and longitudinal research designs are used to investigate individual differences in development. Developmental psychologists ask, for example, whether family backgrounds are linked to individual differences in intellectual development, why some children show delayed or slower growth in intellectual abilities compared with their age peers, and why some adults remain cognitively fit into old age and others show cognitive decline. In addition, developmental researchers are interested in the extent to which cognitive performance (e.g., memory, reasoning, knowledge) can be enhanced at different points in the life course. Carefully designed intervention and training studies are important tools in this respect. Learning about the modifiability (reserve capacity or plasticity) of the cognitive system at different ages helps in better understanding the processes underlying intellectual and cognitive functioning across the life span.

There is general consensus about the importance of investigating three systems of influence on development: age-graded, history-graded, and nonnormative. Each of these systems involves biological and environmental components that contribute to similarities in development as well as to subgroup variations. Age-graded influences include biological and physical changes (e.g., puberty, menopause) as well as exposure to age-related social factors (e.g., schooling, family life cycle, retirement). History-graded influences imply changes in societal structure and function (e.g., economic depression, medical and technical modernization, periods of war or political oppression). Longitudinal research on the developmental trajectories of men and women who were either young children or adolescents during the 1930s economic depression in North America exemplifies this approach (e.g., Elder). Nonnormative influences are conditions that are not associated with chronological age or historical time, but affect an individual's development in important ways (e.g., a lottery win, loss of a leg in an accident).

There is no unified theoretical framework of developmental psychology. Major metatheoretical positions emphasize cognitive structural, biogenetic, psychoanalytical, action-theoretical, social learning, transactional, contextualist, dialectical, and dynamic systems perspectives (for reviews see Bornstein and Lamb; Cairns).

Concepts of change and development

There has been a long-standing debate in the psychological literature about what aspects of change define development and whether or not development occurs across the life span or only in early life (for reviews see Bengtson and Schaie; Cairns; Valsiner). Traditionally, developmental psychology focused primarily on the description and explanation of positive changes (e.g., increased adaptive capacity or growth) in the structure and function of mind and behavior. Change, within this tradition, is considered to reflect development if one or more of the following criteria are met: (1) it is directed toward a state of maturity; (2) it is quantitative and qualitative (stagelike) in nature; (3) it is relatively robust or irreversible; and/or (4) it moves toward greater complexity and differentiation. Using these criteria to define development encourages theoretical precision but also restricts the concept primarily to growth in early life. Is change observed during adulthood and old age associated with development or with processes of aging?

The life-span approach outlined by Paul B. Baltes (1997; Baltes, et al.) proposes that development is not completed at young adulthood (maturity) but extends across the entire life course. Each age period (e.g., infancy, adolescence, adulthood, old age) has its own developmental tasks. When viewed together, however, these age-specific phenomena contribute to continuous (cumulative) and discontinuous (innovative) change throughout life. The great regularity of development observed in infancy and childhood may be attributed to the fact that the biological and cultural influences that shape childhood are more programmed (genetically and societally) than is true for late adulthood. In old age, the conjoint dynamics of biological and cultural influences are less well-orchestrated, in part because the culture of old age is still evolving.

The life-span approach of Baltes and colleagues alerts researchers to the fact that development can be multidirectional in that it involves trajectories of positive growth, stability, and negative change (loss) across the life span. A classic example of this concept is longitudinal research on the trajectories of fluid versus crystallized intelligence during adulthood and into old age (e.g., Schaie). Dimensions of fluid intelligence (e.g., spatial ability, reasoning, perceptual speed) generally show decline beginning in middle age, whereas aspects of crystallized intelligence (e.g., knowledge) remain relatively stable up to at least age eighty.

Expanding the concept of development from a growth model to a multidirectional model led to the insight that development is likely always a combination of gains and losses. A gain in one direction, for example, may exclude alternative pathways of development. The search for gains and losses across the life span has led to much recent research on the plasticity of mind and behavior; the fundamental role of processes of selection, optimization, and compensation in development; and profiles of successful aging.

Jacqui Smith

See also Developmental Tasks; Life Course; Life-Span Development; Selective Optimization with Compensation Theory.

BIBLIOGRAPHY

Baltes, P. B. "On the Incomplete Architecture of Human Ontogeny: Selection, Optimization, and Compensation as Foundation of Developmental Theory." American Psychologist 52 (1997): 366–380.

Baltes, P. B.; Lindenberger, U.; and Staudinger, U. M. "Life-Span Theory in Developmental Psychology." In Handbook of Child Psychology. Vol. 1, Theoretical Models of Human Development, 5th ed. Edited by R. M. Lerner. New York: Wiley, 1998. Pages 1029–1143.

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Developmental psychology

A field of psychology which examines how human behavior changes as a person matures through focusing on biological, emotional, physical, cognitive, and social changes that are age-related, sequential, and long-lasting.

Developmental psychologists study how characteristics and behaviors first appear and how and when they change. They study the relationships between different types of development, such as cognitive and social, as well as individual variations in development, both normal and deviant. Initially, developmental psychology focused on childhood but was subsequently expanded to cover changes that occur over the entire life span, from the intrauterine environment through childhood, adolescence , middle age, and maturity. Three processes that play a central role in development are growth, maturation, and learning. Growth refers to physical changes that are quantitative, such as increases in height or weight. Maturation involves anatomical, neurophysiological, and chemical transformations that change the way a person functions (such as a woman's passage into or out of childbearing age). Learning involves relatively long-term changes in behavior or performance acquired through observation, experience, or training.

One of the oldest questions in developmental psychology involves the nature-nurture controversy , which asks how and to what degree nature (inherited or genetic factors influencing development) contributes to a person's biological, emotional, cognitive, and social development, and to what degree it is the result of nurture (the influence of learning and experience in the environment ). This issue has been debated for centuries by philosophers, who often argued strenuously for the predominance of one influence over the other (a famous example is the British philosopher John Locke's concept of the newborn human being as a blank slate, or tabula rasa, to be formed by experience). Pioneered by the American psychologist Arnold Gesell , the concept of maturation, which is central to developmental psychology, stresses the role of nature in human development. Gesell observed that the motor skills of children develop in a fixed order through a series of stages relatively unaffected by outside influences. The interplay of nature and nurture, rather than the importance of one over the other, however, has gained a greater emphasis in the work of more recent figures, notably the Swiss psychologist Jean Piaget , whose theory of cognitive development in children has been a model for much subsequent work in the field. Going beyond simplistic dichotomies, scientists have been able to gather substantial amounts of specific data on the effects of heredity and environment through family , twin, and adoption studies. Current concepts of maturation focus on models in which each stage of a developmental process is defined not only by innate characteristics but also by increased receptivity (or "readiness") toward certain environmental factors.

Another significant issue in the field of developmental psychology is the question of continuity versus stages, specifically, does an individual's development occur in a gradual and progressive (continuous) fashion, or in a distinct series of discrete stages? In his pioneering theory of cognitive development, Piaget delineated a sequence of developmental stages that occur in a fixed order with each dependent on the previous ones (sensori-motor, preoperational, concrete operational, and formal operational). Subsequent research has challenged some of his assumptions, finding in some cases that children are capable of advanced thinking at younger ages than those posited by Piaget. Observations such as these have led to the conclusion that cognitive development is more uneven and less systematic than previously thought, and that children's reasoning abilities in a specific situation may depend on variables—familiarity with certain objects, language comprehension, and prior experiences— that are not part of Piaget's system. One recent model advances the notion of cognitive development in "pockets" rather than globally uniform levels or stages. Another alternative that has been suggested is an information processing model focusing on gradual quantitative advances in memory and other learning abilities rather than qualitative progress through a series of stages.

In addition to Piaget, another major influence in the area of human development was Erik Erikson , whose eight stages of psychosocial development, encompassing the entire life span from infancy through old age, inspired an interest in the continuation of development past childhood. Erikson's work also popularized the concept of the adolescent "identity crisis" (a term he coined). Yet another type of development that has gained increased interest in recent years is moral development , which has been most extensively investigated by Lawrence Kohlberg . Presenting subjects with hypothetical moral dilemmas, Kohlberg found that moral reasoning in children develops through three distinct levels (consisting of two stages each) between the age of seven and adolescence. Like Piaget's theory, Kohlberg's stages do not necessarily occur at a given age but they do occur consistently in a given order. Also, not all individuals reach the final stage, at which following rules and obeying the social order is superseded by the imperative of the individual conscience to obey ethical principles that may transcend the law. The universality of some of Kohlberg's findings has been challenged in terms of applicability to non-Western cultures and women (Kohlberg's research focused on men). When Carol Gilligan questioned subjects about moral conflicts, the reactions of male and female respondents differed significantly, and Gilligan drew up her own model for women.

See also Cognitive development; Cognitive psychology; Information-processing theory

Further Reading

Anderson, Clifford. The Stages of Life: A Groundbreaking Discovery: the Steps to Psychological Maturity. New York: Atlantic Monthly Press, 1995.

Berger, Kathleen Stassen. The Developing Person Through the Life Span. 2nd ed. New York: Worth Publishers, 1988.

Cicchetti, Dante, and Donald J. Cohen, eds. Developmental Psychopathology. New York: J. Wiley, 1995.

developmental psychology Study of changes in behaviour through all life stages from the fetus to old age. Psychologists study normal growth, change, and self-actualization, and also life-stage related problems. See also child psychology