Developmental psychology is the scientific study of progressive psychological changes that occur in human beings as they age. Originally concerned with infants and children, it is often called child development or child psychology. As the study of other periods of great change such as adolescence and aging were added, it now encompasses the entire life span, and is also referred to as Lifespan psychology. This field examines change across a broad range of topics including: Perceptual motor skills, problem solving abilities, acquisition of language, moral understanding, and identity formation. Developmental psychology informs several applied fields, including educational psychology, child psychopathology and forensic psychology, and also complements several other basic research fields in psychology, including social psychology, cognitive psychology, and comparative psychology. Ultimately, the goal of those working in the field of developmental psychology is to understand the complexities of human nature and the processes and conditions under which human beings, from infancy into adulthood and beyond, learn to become mature human beings who fulfill their individual potential, live in service to their community, and exercise loving stewardship over the environment.
Developmental psychologists study the changes that occur as development proceeds. They examine both the changes themselves, and what causes them. Thus, developmental psychology has two main goals (Vasta et al. 1998):
The scientific study of children began in the late nineteenth century, and blossomed in the early twentieth century as pioneering psychologists sought to uncover the secrets of human behavior by studying its development. Developmental psychology made an early appearance in a more literary form, however. William Shakespeare had his melancholy character, "Jacques" (in As You Like It), articulate the "seven ages of man," which included three stages of childhood and four of adulthood.
Three early scholars, John Locke, Jean-Jacques Rousseau, and Charles Darwin proposed theories of human behavior that are the "direct ancestors of the three major theoretical traditions" (Vasta et al, 1998, p. 10) of developmental psychology today. Locke, a British empiricist, adhered to a strict environmentalist position, that the mind of the newborn as a tabula rasa ("blank slate") on which knowledge is written through experience and learning. Rousseau, a Swiss philosopher who spent much of his life in France, proposed a nativistic model in his famous novel Emile, in which development occurs according to innate processes progressing through three stages: Infans (infancy), puer (childhood), and adolescence. Finally, the work of Darwin, the British biologist famous for his theory of evolution, led others to suggest that development proceeds through evolutionary recapitulation, with many human behaviors having their origins in successful adaptations in the past as "ontogeny recapitulates phylogeny."
G. Stanley Hall, called the "father" of developmental psychology, is credited with conducting the first systematic studies of children. These involved questionnaires, which unfortunately were not structured in a way as to produce useful data. He was also unsuccessful in research that attempted to show that the child's development recapitulates the evolution of the species. His major contributions to the field are that he taught the first courses in child development, several of his students becoming leading researchers in the field, and he established scientific journals for the publication of child development research.
John B. Watson originated the Behaviorist approach to psychology at the beginning of the twentieth century. He believed, based on Locke's environmentalist position, that human behavior can be understood in terms of experiences and learning. Determined that experimental psychology follow the scientific method he rejected the introspective approach, which attempted to understand internal mental experiences based on self-reports, and called instead for objective study of observable, measurable behaviors. Watson's 1928 book, Psychological Care of the Infant and Child, presented his view that all behavior is the product of environment and experience with no important contribution by biological factors, and that all learning takes place through a process of association or "conditioning," as proposed by Ivan Pavlov.
Sigmund Freud's model of "psychosexual development" grew out of his psychoanalytic approach to human personality and psychopathology. In sharp contrast to the objective approach espoused by Watson, Freud based his model of child development on his own and his patients' recollections of their childhood. He developed a stage model of development in which the libido, or sexual energy, of the child focuses on different "zones" or areas of the body as the child grows to adulthood. Freud's model is an "interactionist" one, since he believed that although the sequence and timing of these stages is biologically determined, successful personality development depends on the experiences the child has during each stage. Although the details of Freud's developmental theory have been widely criticized, his emphasis on the importance of early childhood experiences, prior to five years of age, has had a lasting impact.
Arnold Gesell, a student of G. Stanley Hall, carried out the first large-scale detailed study of children's behavior. His research revealed consistent patterns of development, supporting his view that human development depends on biological "maturation," with the environment providing only minor variations in the age at which a skill might emerge but never affecting the sequence or pattern. Gesell's research produced norms, such as the order and the normal age range in which a variety of early behaviors such as sitting, crawling, and walking emerge. In conducting his studies, Gesell developed sophisticated observational techniques, including one-way viewing screens and recording methods that did not disturb the child.
Jean Piaget is considered one of the most influential psychologists of the twentieth century, and his stage theory of cognitive development revolutionized our view of children's thinking and learning. His work inspired more research than any other theorist, and many of his concepts are still foundational to developmental psychology. His interest lay in children's knowledge, their thinking, and the qualitative differences in their thinking as it develops. Although he called his field "genetic epistemology," stressing the role of biological determinism, he also assigned great importance to experience. In his view, children "construct" their knowledge through processes of "assimilation," in which they evaluate and try to understand new information, based on their existing knowledge of the world, and "accommodation," in which they expand and modify their cognitive structures based on new experiences.
Developmental psychology employs many of the research methods used in other areas of psychology. However, infants and children cannot always be tested in the same ways as adults, and so different methods are often used to study development.
When studying infants, a method often used to assess their performance is habituation methodology. This allows researchers to obtain information about what types of stimuli an infant is able to discriminate. Infants are habituated to a particular stimulus and are then tested using different stimuli to evaluate discrimination. The critical measure in habituation is the infants' level of interest.
Several measures can be used to measure infants' preference. These include the high-amplitude sucking procedure, in which infants' level of sucking on a pacifier varies depending on their level of interest, the conditioned foot-kick procedure, in which infants move their legs to indicate preference, and the head-turn preference procedure, in which infants level of interest is measured by the amount of time spent looking in a particular direction. A key feature of all these methods is that the infant controls the stimuli being presented. Typically, infants prefer stimuli that are novel relative to those they have encountered previously, and therefore their responses to a stimulus recognized as novel is measurably distinct from their responses to those to which they have already habituated. This gives researchers a means of measuring discrimination. If an infant is able to discriminate between the habituated stimulus and a novel stimulus, they will show a preference for the novel stimulus. If, however, the infant cannot discriminate between the two stimuli, they will not show a preference for one over the other.
When studying older children, especially adolescents, adult measurements of behavior can often be used. However, they may need to be simplified to allow children to perform the tasks successfully.
Developmental psychology is concerned with many different components of human psychology and how they change over time. These different aspects of development complement many other areas of psychology, including studies of cognition, social abilities, and personality.
Cognitive development is primarily concerned with the ways in which infants and children acquire and advance their cognitive abilities. Major topics in cognitive development are the study of language acquisition and the development of perceptual-motor skills. Piaget was one of the influential early psychologists to study the development of cognitive abilities. His theory suggested that cognitive development proceeds through a set of stages from infancy to adulthood. Not only did Piaget himself carry out extensive work, carried on by his collaborators, but numerous developmental psychologists around the world have conducted research based on his theory. Although many have sought to disprove his findings and reject his theories, Piaget's influence has been undeniable and greatly advanced our understanding of children's development.
Social psychology is the study of the nature and causes of human social behavior, with an emphasis on how people think about each other and how they relate to each other. In early-modern social science theory, John Stuart Mill, Auguste Comte, and others, laid the foundation for social psychology by asserting that human social cognition and behavior could, and should, be studied scientifically like any other natural science. Developmental social psychologists study the way infants, children, adolescents, and adults interact with others in various social environments.
For example, Attachment theory, developed by John Bowlby (Bowlby 1983), focuses on the close, intimate, emotionally meaningful relationship that develops between infants and their mothers or primary caregivers. This "attachment" is described as a biological system that evolved to ensure the survival of the infant. Attachment behavior is evoked whenever the person is threatened or stressed and involves actions to move toward the person(s) who create a sense of physical, emotional, and psychological safety for the individual. Its methods of study involve such approaches as the "Strange Situation Protocol" developed by Mary Ainsworth, in which an infant's reaction to being reunited with their mother (or primary caregiver) after interaction with a stranger is used as an indicator of the nature of the bond between mother and child.
An individual's personality is a collection of emotional, thought, and behavioral patterns unique to a person that is consistent over time. Many personality theorists regard personality as a combination of various "traits," that determine how an individual responds to various situations. Some psychologists take a biological view of personality and research temperaments in children and heritability in adult twins, hoping is to find genetic components underlying the external expressions of personality.
Others consider that these ways of responding to our environment are built up over time through experiences. Social-cognitive theorists emphasize the situation the person is in and the person's expectations, habits, and belief system. This approach regards the environment, cognitions, and a person's behavior as all having an influence on each other in a complex pattern that shapes each individual's distinctive personality. Researchers in this approach study the various environmental influences that lead to particular types of personality formation.
Sigmund Freud and others following his work emphasized stages of personality development. In Freud's model, the first few years of life are crucial in forming the personality, as the libido that each child is born with is biologically guided to difference locations on the body, allowing the child to experience pleasure in different ways. The amount of pleasure the child is able to experience, which is affected by adult interactions, determines whether the libido is satisfied and moves on successfully to the next zone or whether the individual will become fixated on a particular type of pleasure seeking, leading to personality defects and even neuroses in adult life. While many details of Freud's model have been disputed and disproved by later research, his influence on the field has been enormous.
Some examples of questions addressed by developmental psychologists include the following:
The ways in which these questions are answered relates to three major theoretical issues in developmental psychology:
A significant question in developmental psychology is the relation between innateness and environmental influence in regard to any particular aspect of development. This is often referred to as "nature versus nurture" debate, or nativism versus empiricism. A nativist account of development would argue that the processes in question are innate, that is, they are specified by the organism's genes. An empiricist perspective would argue that those processes are acquired in interaction with the environment. Developmental psychologists rarely take such extreme positions with regard to most aspects of development; rather they investigate the relationship between innate and environmental influences on the development of particular processes.
One area where this innateness debate has been prominently portrayed is in research on language acquisition. A major question in this area is whether or not certain properties of human language are specified genetically or can be acquired through learning. The nativist position argues that the input from language is too impoverished for infants and children to acquire the structure of language. Linguist Noam Chomsky has asserted that, evidenced by the lack of sufficient information in the language input, there is a "universal grammar" that applies to all human languages and is pre-specified. This has led to the idea that there is a special cognitive module suited for learning language, often called the "language acquisition device."
The empiricist position on the issue of language acquisition suggested that the language input does provide the necessary information required for learning the structure of language and that infants acquire language through a process of statistical learning. From this perspective, language can be acquired via general learning methods that also apply to other aspects of development, such as perceptual learning. There is a great deal of evidence for components of both the nativist and empiricist position, and this has been a hotly debated research topic in developmental psychology.
Another area that illustrates the role of experience has been gender role development. The finding that there were differences in spatial abilities between males and females (Halpern 1986) suggested several possible explanations. The brains of males and females could be structured differently (nature); boys could receive more encouragement from adults to engage in activities that promote spatial skills (environment); or boys could have an innate preference for such activities and improve their abilities through greater practice than girls, who prefer other activities (interaction).
A long-standing debate in developmental psychology is whether development occurs continuously, with one behavior or skill building upon another, such that later development is tied and can be predicted from what occurred early in life, or whether there is discontinuity as new behaviors and skills emerge at certain stages in life. The continuity model regards development as basically quantitative, with new skills learned and added to the previous, simpler set. Such a view is generally found in the work of Behaviorists.
The alternative view is that development occurs in stages, distinct phases in an individual's development. These stages are viewed not as simple accumulation of new skills, but an abrupt, qualitative change in the individual's behavior. Stage theorists generally posit stages that occur in a fixed order, within particular time frames, and that are universal across all individuals (although some may not reach the highest stages).
Many theories in psychology characterize development in terms of stages:
Psychologists generally agree that neither approach is complete—rather, some processes may be better described as continuous and others as occurring through stages.
The issue of whether to study normative development or the individual differences in development is more of a matter of preference than theoretical debate. The normative approach is valuable in applications such as education, where understanding the normal range of abilities at different age groups allows teachers to prepare appropriate lessons, while studies of sensorimotor skills prove useful clinical diagnostic tools for pediatricians. Researchers such as Arnold Gesell pioneered studies of such normative data.
Studies of differences in development are more attuned to investigations of the underlying processes and the factors that promote and hinder development. Research on development of intelligence and creativity has often focused on studying individual differences in an attempt to understand the nature of such complex human abilities, whether there are significant innate differences among individuals, and how each person can achieve their full potential in these areas.
Developmental psychologists usually focus on a particular age group and the development of particular skills during that time period—perceptual-motor skills during infancy, gender roles during adolescence, and so forth. Additionally, they have a particular theoretical orientation—their view of how development occurs and the factors they believe to be most significant in producing change in children's behavior. While there are many approaches, four of the most significant are described here.
The roots of the cognitive-developmental approach lie in the interest of those in this tradition to discover the structure or organization of children's knowledge. Typifying this approach is the Piagetian model of cognitive development.
Piaget regarded the development of human cognition as a complex process involving inbuilt biological mechanisms whose function is to construct "schemes" of knowledge through interaction with the environment. Based on initial observations of his own children, followed by extensive laboratory experiments, Piaget postulated four basic stages of child development:
Developmental psychology is concerned not only with describing the characteristics of psychological change over time, but also seeks to explain the principles and internal workings underlying these changes. An example of this type of approach uses information processing models (Klahr & Wallace 1976; Siegler 1978). Regarding the human mind in ways similar to that of a computer—with stimulation from the outside world as input, mental processes acting on the input, leading to behavior that forms the output of the system—this approach has led to detailed study of the child's problem solving abilities at different ages.
Other theorists, such as Lev Vygotsky, have regarded social cognition, or knowledge about people and social processes, as fundamental to human development. His theory proposed that children internalize, primarily through the use of language, large amounts of knowledge and thought from their surrounding culture as a result of social interactions.
Environmental-learning approaches are based on the Behaviorist assumption that learning and conditioning principles account for children's development. B.F. Skinner expanded John B. Watson's model of learning, which was based on Ivan Pavlov's classical conditioning of reflexes, adding the conditioning of "operant" or voluntary behaviors. Since the majority of human behaviors are of this nature, dependent on their consequences—pleasant consequences (rewards) increasing the likelihood and unpleasant consequences (punishments) decreasing the likelihood that they will be reproduced—Skinner's model proved useful in understanding many aspects of children's behavior.
One area that such a learning theory could not explain, however, is the type of learning whereby a child learns by observing a model. Termed Observational learning or "social learning" by Albert Bandura (1985), this process allows children to imitate the behavior they observe in another—parent, teacher, friend, sibling, television personality, and so forth—when they see it has reinforcing consequences and to inhibit such behavior when punishment is observed as the consequence.
The ethological approach studies development from an evolutionary perspective, regarding certain types of behavior as the result of historical experiences of the species. Ethologists have often studied non-human behavior, believing mechanisms of development to be common to all living creatures. Pioneers in this work include Konrad Lorenz and Niko Tinbergen, whose pioneering research led to their joint award of a Nobel Prize in 1973.
Applying the ethological approach specifically to human development, E.O. Wilson developed the theory of sociobiology, suggesting that social behaviors that are adaptive for survival are transmitted genetically. Less controversially, John Bowlby's research on the bond between mother and infant—considered essential for survival in the ethological approach—suggested that for attachment to develop successfully it must occur during a short "sensitive period."
The ecological approach is not so much a different theoretical model as a different way of looking at the factors that influence human development. Psychologists, in their effort to study human behavior scientifically devised complex laboratory settings in which to study children's behavior under experimental control. The problem with this approach, however, is that child development does not occur in the laboratory; rather it takes place in the home with family members, in school with peers, in the neighborhood, and so forth. Development always occurs in a particular social context.
Urie Bronfenbrenner (1979) developed what is known as "Ecological Systems Theory" to describe how human social relationships function in, and are affected by, their various social environments, or "human ecologies." Building on work by Soviet developmental psychologist Lev Vygotsky and German-born psychologist Kurt Lewin, Bronfenbrenner delineated four types of nested systems, with bi-directional influences within and between systems.
This theory has had widespread influence on the way psychologists and others approached the study of human beings and their environments. It has been said that before Bronfenbrenner, child psychologists studied the child, sociologists examined the family, anthropologists the society, economists the economic framework of the times, and political scientists the structure. As a result of Bronfenbrenner's groundbreaking work these environments—from the family to economic and political structures—became viewed as part of the life course from childhood to adulthood.
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