Developmental psychology is the scientific study of progressive psychological changes that occur in human beings as they age. Originally concerned with infants and children, and later other periods of great change such as adolescence and aging, it now encompasses the entire life span. This field examines change across a broad range of topics including motor skills and other psycho-physiological processes, problem solving abilities, conceptual understanding, acquisition of language, moral understanding, and identity formation.
Developmental psychologists investigate key questions, such as whether children are qualitatively different from adults or simply lack the experience that adults draw upon. Other issues that they deal with is the question of whether development occurs through the gradual accumulation of knowledge or through shifts from one stage of thinking to another; or if children are born with innate knowledge or figure things out through experience; and whether development driven by the social context or by something inside each child.
Developmental psychology informs several applied fields, including: educational psychology, child psychopathology and developmental forensics. Developmental psychology complements several other basic research fields in psychology including social psychology, cognitive psychology, and comparative psychology.
Many theoretical perspectives attempt to explain development, among the most prominent are: Jean Piaget's Stage Theory, Lev Vygotsky's Social Contextualism (and its heir, the Development in Context or Human Ecology theory of Urie Bronfenbrenner), and especially the information processing framework employed by cognitive psychology.
Historical theories continue to provide a basis for additional research, among them are Erik Erikson's eight stages of psychosocial development and John B. Watson's and B. F. Skinner's Behaviorism. Many other theories are prominent for their contributions to particular aspects of development. For example, Attachment theory describes kinds of interpersonal relationships and Lawrence Kohlberg describes stages in moral reasoning.
Ecological Systems Theory
Generally regarded as one of the world's leading scholars in the field of developmental psychology, Bronfenbrenner's primary contribution was his Ecological Systems Theory, in which he delineated four types of nested systems, with bi-directional influences within and between systems.
- Microsystem: Immediate environments (family, school, peer group, neighborhood, and childcare environments)
- Mesosystem: A system comprised of connections between immediate environments (i.e., a child’s home and school)
- Exosystem: External environmental settings which only indirectly affect development (such as parent's workplace)
- Macrosystem: The larger cultural context (Eastern vs. Western culture, national economy, subculture)
The person's own biology is considered part of the microsystem; thus the theory has recently sometimes been called Bio-Ecological Systems Theory.
Each system contains roles, norms and rules that can powerfully shape development. For example, an inner-city black family faces many challenges which an affluent white family in a gated community does not, and vice versa. The inner-city black family is more likely to experience environmental hardships, such as teratogens and crime. The sheltered white family on the other hand is more likely to lack the nurturing support of extended family.
The major statement of this theory, The ecology of human development (1979) 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 in "human ecology," a field that he created, these environments - from the family to economic and political structures - were viewed as part of the life course from childhood to adulthood.
Role of experience
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" 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. Today developmental psychologists rarely take such extreme positions with regard to most aspects of development; rather they investigate, among many other things, the relationship between innate and environmental influences. One of the ways in which this relationship has been explored in recent years is through the emerging field of evolutionary developmental psychology.
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 asserts 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 suggests 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 is a hotly debated research topic in developmental psychology.
On the other hand, Chomsky's critique of a specific nativist position on this issue, radical behaviorist Burrhus Frederic Skinner's Verbal Behavior written in 1957, is widely considered among developmental psychologists to have sparked the decline in influence of behaviorism and signaled the beginning of the cognitive revolution in psychology.
Mechanisms of 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. Understanding these factors is aided by the use of models. Developmental models are often computational, but they do not necessarily need to be. A model must simply account for the means by which a process takes place. This is sometimes done in reference to changes in the brain that may correspond to changes in behavior over the course of the development. Computational accounts of development often use either symbolic, connectionist (neural network), or dynamical systems models to explain the mechanisms of development.
History of developmental psychology
The modern form of developmental psychology has its roots in the rich psychological tradition represented by Heraclitus, Aristotle and Descartes. William Shakespeare had his melancholy character Jacques (in As You Like It) articulate the seven ages of man: these included three stages of childhood and four of adulthood. In the mid-eighteenth century Jean Jacques Rousseau described three stages of childhood: infans (infancy), puer (childhood) and adolescence in Emile: Or, On Education. Rousseau's ideas were taken up strongly by educators at the time.
In the late nineteenth century, psychologists familiar with the evolutionary theory of Darwin began seeking an evolutionary description of psychological development; prominent here was G. Stanley Hall, who attempted to correlate ages of childhood with previous ages of mankind.
A more scientific approach was initiated by James Mark Baldwin, who wrote essays on topics that included Imitation: A Chapter in the Natural History of Consciousness and Mental Development in the Child and the Race: Methods and Processes. In 1905, Sigmund Freud articulated five psychosexual stages. Later, Rudolf Steiner articulated stages of psychological development throughout human life. The first three of these stages, which correspond closely with Piaget's later-described stages of childhood, were first presented in Steiner's 1911 essay The Education of the Child; his descriptions have been taken up by educators (in the Waldorf Schools) and by psychologists (in biographical therapy; see the works of Bernard Lievegoed). By the early to mid-twentieth century, the work of Vygotsky and Piaget, mentioned above, had established a strong empirical tradition in the field.
The role of mothers
Traditionally mothers (and women generally) were emphasized to the exclusion of other caretakers. This has begun to change, with the emphasis now placed on a primary caretaker (regardless of gender or biological relation), as well as all persons directly or indirectly influencing the child (the family system).
For example, the traditional father had little to do with an infant directly, but his method of interacting with the mother (supportive, abusive, neglectful) had a great deal of impact on the infant indirectly.
Stages of development
The prenatal development of human beings is viewed in three separate stages:
These stages are not the same as the trimesters of a woman's pregnancy.
The germinal stage least resembles a grown human. It begins when a sperm penetrates an egg in the act of conception (normally the result of sexual intercourse between a man and a woman). At this point a zygote is formed. Through the process of mitosis the cells divide and double.
The embryonic stage occurs once the zygote has firmly implanted itself into the uterine wall. It is in this stage that the vital organs are formed, and while the external body is still extremely dissimilar from an adult human, some features such as eyes and arms, and eventually ears and feet become recognizable.
The fetal period is when the brain most substantially forms, becoming more and more complex over the last few months.
Ultrasound uses sound waves and a computer monitor, and is non-invasive, thus minimizing potential harm to fetus and mother. Unfortunately its ability to determine potential defect is also far less comprehensive than more risky methods.
Chorionic villus sampling is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. It entails getting a sample of the chorionic villus (placental tissue) and testing it. It is generally carried out only on pregnant women over the age of 35 and those who have a higher risk of Down syndrome and other chromosomal conditions.
The advantage of CVS is that it can be carried out at 10-12 weeks of pregnancy, earlier than amniocentesis (which is carried out at 15-18 weeks). However, it is more risky than amniocentesis, with a 1 in 100 to 200 risk that it will cause a miscarriage.
Amniocentesis is another medical procedure used for prenatal diagnosis, in which a small amount of amniotic fluid is extracted from the amnion around a developing fetus. It is usually offered when there may be an increased risk for genetic conditions (i.e. Down syndrome, sickle-cell disease, cystic fibrosis, etc) in the pregnancy. Amniocentesis done in the second trimester is often said to have a risk of fetal death between about 1 in 400 and 1 in 200. Often, genetic counseling is done before amniocentesis, or other types of genetic testing, is offered.
Although difficult, some methods of treating fetal disorders have been developed, both surgical and drug based. Genetic testing prior to pregnancy is also increasingly available.
From birth until the child begins to speak, they are referred to as an infant. Developmental psychologists vary widely in their assessment of the infants psychology, and the influence the outside world has upon it, but certain aspects are relatively clear.
While no agreement has yet been reached regarding the level of stimulation an infant requires, we are well aware that a normal level of stimulation is very important, and that a lack of stimulation and affection can result in retardation and a host of other developmental and social disorders. Some feel that classical music, particularly Mozart is good for an infants mind. While some tentative research has shown it to be helpful to older children, no conclusive evidence is available involving infants.
The majority of an infants time is spent in sleep. At first this sleep is evenly spread throughout the day and night, but after a couple of months they generally become diurnal.
Infants can be seen to have 6 states, grouped into pairs:
- quiet sleep and active sleep (dreaming, when REM occurs)
- quiet waking, and active waking
- fussing and crying
Infants respond to stimuli differently when in these different states. Habituation is frequently used in testing psychological phenomenon. Both infants and adults look less and less as a result of consistent exposure to a particular stimulus. The amount of time spent looking to a presented alternate stimulus (after habituation to the initial stimulus) is indicative of the strength of the remembered percept of the previous stimulus, or dishabituation.
Habituation is used to discover the resolution of perceptual systems, for example, by habituating a subject to one stimulus, and then observing responses to similar ones, one can detect the smallest degree of difference that is detectable by the subject.
Infants have a wide variety of reflexes, some of which are permanent (blinking, gagging), and others transient in nature. Some with obvious purposes, some are clearly vestigal and some do not have obvious purposes. Primitive reflexes reappear in adults under certain conditions. Namely, neurological conditions like dementia, traumatic lesions, etc. A partial list of infantile reflexes includes:
- Moro reflex or startle reflex
- Tonic neck reflex or fencer's reflex
- Rooting reflex, sucking reflex, suckling reflex: it can be initiated be scratching the infants cheek and the reaction is pursing of the lips for sucking, that's why it is also called sucking reflex.
- Stepping reflex, step-up reflex: it can be initiated if you support the infant upright from its armpits below a given surface so the baby lifts its foot and steps up on the surface (like climbing a stair).
- Grasp reflex: it can be initiated by scratching baby's palm.
- Parachute reflex
- Plantar reflex or Babinski reflexdistinct components:
Infants have particularly poor vision, and are legally blind. They are capable of sight, however blurry. This improves over time, based on experience. Infants less than 2 months old are also thought to be color blind.
Hearing is well developed prior to birth however, and a preference for their mothers heartbeat is well established. Infants are fairly good at detecting the direction from which a sound comes, and by 18 months their hearing ability is approximately equal to that of adults.
Smell and taste are present, with infants having been shown to prefer the smell and taste of a banana, while rejecting the taste of shrimp. There is good evidence for infants preferring the smell of their mother to that of others.
Infants have a fully developed sense of touch at birth, and the myth believed by some doctors even today that infants feel no pain is inaccurate. Doctors are slowly becoming aware of the need for pain prevention for newborns.
- The first sub-stage occurs from birth to six weeks and is associated primarily with the development of reflexes. Three primary reflexes are described by Piaget: sucking of objects in the mouth, following moving or interesting objects with the eyes, and closing of the hand when an object makes contact with the palm (palmar grasp). Over these first six weeks of life, these reflexes begin to become voluntary actions; for example, the palmar reflex becomes intentional grasping. (Gruber and Vaneche, 1977).
- The second sub-stage occurs from six weeks to four months and is associated primarily with the development of habits. Primary circular reactions or repeating of an action involving only ones own body begin. An example of this type of reaction would involve something like an infant repeating the motion of passing their hand before their face. Also at this phase, passive reactions, caused by classical or operant conditioning, can begin (Gruber et al., 1977).
- The third sub-stage occurs from four to nine months and is associated primarily with the development of coordination between vision and prehension. Three new abilities occur at this stage: intentional grasping for a desired object, secondary circular reactions, and differentiations between ends and means. At this stage, infants will intentionally grasp the air in the direction of a desired object, often to the amusement of friends and family. Secondary circular reactions, or the repetition of an action involving an external object occur begin; for example, moving a switch to turn on a light repeatedly. The differentiation between means also occurs. This is perhaps one of the most important stages of a child's growth as it signifies the dawn of logic (Gruber et al., 1977). Towards the late part of this sub-stage infants begin to have a sense of object permanence, passing the A-not-B error test.
- The fourth sub-stage occurs from nine to twelve months and is associated primarily with the development of logic and the coordination between means and ends. This is an extremely important stage of development, holding what Piaget calls the "first proper intelligence." Also, this stage marks the beginning of goal orientation, the deliberate planning of steps to meet an objective (Gruber et al. 1977).
- The fifth sub-stage occurs from twelve to eighteen months and is associated primarily with the discovery of new means to meet goals. Piaget describes the child at this juncture as the "young scientist," conducting pseudo-experiments to discover new methods of meeting challenges (Gruber et al. 1977).
- The sixth sub-stage is associated primarily with the beginnings of insight, or true creativity. This marks the passage into the preoperational stage.
When studying infants, the habituation methodology is an example of a method often used to assess their performance. This method allows researchers to obtain information about what types of stimuli an infant is able to discriminate. In this paradigm, 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. Typically, infants prefer stimuli that are novel relative to those they have encountered previously. Several methods are used to measure infants' preference. These include the high-amplitude sucking procedure, in which infants suck on a pacifier more or less 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, in each situation, the infant controls the stimuli being presented. 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.
Object permanence is an important stage of cognitive development for infants. Numerous tests regarding it have been done, usually involving a toy, and a crude barrier which is placed in front of the toy, and then removed, repeatedly. In sersorimotor stages 1 and 2, the infant is completely unable to comprehend object permanence. Jean Piaget conducted experiments with infants which led him to conclude that this awareness was typically achieved at eight to nine months of age. Infants before this age are too young to understand object permanence, which explains why infants at this age do not cry when their mothers are gone. "Out of sight, out of mind." A lack of Object Permanence can lead to A-not-B errors, where children reach for a thing at a place where it should not be.
Schools of psychology
Cognitive development is primarily concerned with the ways in which infants and children acquire cognitive abilities. Major topics in cognitive development are the study of language acquisition and the development of perceptual and motor skills. Piaget was one of the influential early psychologists to study the development of cognitive abilities. His theory suggests that development proceeds through a set of stages from infancy to adulthood and that there is an end point or goal. Other accounts such as that of Lev Vygotsky’s have suggested that development does not progress through stages rather that the development process that begins at birth and continues until death is too complex for such structure and finality. Rather, from this viewpoint, developmental processes proceed more continuously, thus it should be analyzed, instead of a product to be obtained.
Social psychology is the study of the nature and causes of human social behavior, with an emphasis on how people think towards each other and how they relate to each other. As the mind is the axis around which social behavior pivots, social psychologists tend to study the relationship between mind(s) and social behaviors. In early-modern social science theory, John Stuart Mill, 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 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, so different methods are often used to study development.
Child research methods
When studying older children, especially adolescents, adult measurements of behavior can often be used, but they may need to be simplified to allow children to perform certain tasks.
Developmental psychologists have a number of methods to study changes in individuals over time.
In a longitudinal study, a researcher observes many individuals born at or around the same time (a cohort) and carries out new observations as members of the cohort age. This method can be used to draw conclusions about which types of development are universal (or normative) and occur in most members of a cohort. Researchers may also observe ways in which development varies between individuals and hypothesize about the causes of variation observed in their data. Longitudinal studies often require large amounts of time and funding, making them unfeasible in some situations. Also, because members of a cohort all experience historical events unique to their generation, apparently normative developmental trends may in fact be universal only to their cohort.
In a cross-sectional study, a researcher observes differences between individuals of different ages at the same time. This generally requires less resources than the longitudinal method, and because the individuals come from different cohorts, shared historical events are not so much of a confounding factor. By the same token, however, cross-sectional research may not be the most effective way to study differences between participants, as these differences may result not from their different ages but from their exposure to different historical events.
An accelerated longitudinal design or cross-sequential study combines both methodologies. Here, a researcher observes members of different birth cohorts at the same time, and then tracks all participants over time, charting changes in the groups. By comparing differences and similarities in development, one can more easily determine what changes can be attributed to individual or historical environment, and which are truly universal. Clearly such a study can be even more resource-consuming than a longitudinal study.
Additionally, these are all correlational, not experimental, designs, and so one cannot readily infer causation from the data they yield. Nonetheless, correlational research methods are common in the study of development, in part due to ethical concerns. In a study of the effects of poverty on development, for instance, one cannot easilly randomly assign certain families to a poverty condition and others to an affluent one, and so observation alone has to suffice.
Theorists & theories
- Jean Piaget, Theory of cognitive development
- Erik Erikson, Erikson's stages of psychosocial development
- Lawrence Kohlberg, Kohlberg's stages of moral development
- James W. Fowler, Stages of faith development
- Annotated Bibliography: a list of prominent works in developmental psychology
- Developmental stage
- Evolutionary developmental psychology
- Life history theory
- Developmental Psychology: lessons for teaching and learning developmental psychology
- GMU’s On-Line Resources for Developmental Psychology: a web directory of Developmental Psychology organizations
- Psychology Resources
- Evolutionary Developmental Psychology (in the journal Child Development)
- Child Development and Evolutionary Psychology (in the journal Child Development)
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