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.
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.