Developmental Psychology

Developmental psychology, also known as human development, is the scientific study of systematic psychological changes, emotional changes, and perception changes that occur in human beings over the course of their life span. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and the entire life span. This field examines change across a broad range of topics including motor skills and other psycho-physiological processes; cognitive development involving areas such as problem solving, moral understanding, and conceptual understanding; language acquisition; social, personality, and emotional development; and self-concept and identity formation.

Developmental psychology includes issues such as the extent to which development occurs through the gradual accumulation of knowledge versus stage-like development, or the extent to which children are born with innate mental structures versus learning through experience. Many researchers are interested in the interaction between personal characteristics, the individual's behavior, and environmental factors including social context, and their impact on development; others take a more narrowly-focused approach.

Developmental psychology informs several applied fields, including: educational psychology, child psychopathology, and forensic developmental psychology. Developmental psychology complements several other basic research fields in psychology including social psychology, cognitive psychology, ecological psychology, and comparative psychology.

Approaches
Many theoretical perspectives attempt to explain development; among the most prominent are: Jean Piaget's Stage Theory, Lev Vygotsky's Social constructivism (and its heirs, the Cultural Theory of Development of Michael Cole, and the Ecological Systems Theory of Urie Bronfenbrenner), Albert Bandura's Social learning theory, and the information processing framework employed by cognitive psychology.

To a lesser extent, 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. For more on behaviorism's role see Behavior analysis of child development).

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.

Theorists and theories
Piaget was a French speaking Swiss theorist who posited that children learn by actively constructing knowledge through hands-on experience He suggested that the adult's role in helping the child learn was to provide appropriate materials for the child to interact and construct. He would use Socratic questioning to get the children to reflect on what they were doing. He would try to get them to see contradictions in their explanations. He also developed stages of development. His approach can be seen in how the curriculum is sequenced in schools, and in the pedagogy of preschool centers across the United States.

Vygotsky's cultural–historical theory
Vygotsky was a theorist from the Soviet era, who posited that children learn through hands-on experience, as Jean Piaget suggested. However, unlike Piaget, he claimed that timely and sensitive intervention by adults when a child is on the edge of learning a new task (called the "zone of proximal development") could help children learn new tasks. Martin Hill stated that "The world of reality does not apply to the mind of a child." This technique is called "scaffolding," because it builds upon knowledge children already have with new knowledge that adults can help the child learn. Vygotsky was strongly focused on the role of culture in determining the child's pattern of development, arguing that development moves from the social level to the individual level.

Ecological Systems Theory
Also called "Development in Context" or "Human Ecology" theory, Ecological Systems Theory, originally formulated by Urie Bronfenbrenner specifies four types of nested environmental systems, with bi-directional influences within and between the systems. The four systems are microsystem, mesosystem, exosystem, and macrosystem. Each system contains roles, norms and rules that can powerfully shape development. Since its publication in 1979, Bronfenbrenner's major statement of this theory, The Ecology of Human Development[3] has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of this conceptualization of development, these environments—from the family to economic and political structures—have come to be viewed as part of the life course from childhood through adulthood.

Attachment theory
Attachment theory, originally developed by John Bowlby, focuses on open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. Attachment feeds on body contact and familiarity. Later Mary Ainsworth developed the Strange Situation Protocol and the concept of the secure base. See also the critique by developmental psychology pioneer Jerome Kagan.

Unfortunately, there are situations that inhibit a child from forming attachments. Some babies are raised without the stimulation and attention of a regular caregiver, or locked away under conditions of abuse or extreme neglect. The possible short-term effects of this deprivation are anger, despair, detachment, and temporary delay in intellectual development. Long-term effects include increased aggression, clinging behavior, detachment, psychosomatic disorders, and an increased risk of depression as an adult. 

Nature/nurture
A significant issue in developmental psychology is the relationship 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 empiricist position on the issue of language acquisition suggests that the language input provides 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. 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. Chomsky's critique of the behaviorist model of language acquisition is regarded by many as a key turning point in the decline in the prominence of the theory of behaviorism generally. But Skinner's conception of "Verbal Behavior" has not died, perhaps in part because it has generated successful practical applications.

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. Psychologists have attempted to better understand these factors by using models. Developmental models are sometimes computational, but they do not 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.

Cognitive development
Cognitive development is primarily concerned with the ways in which infants and children acquire, develop, and use internal mental capabilities such as problem solving, memory, and language. 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, have suggested that development does not progress through stages, but rather that the developmental 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 development should be analyzed, instead of treated as a product to be obtained.

K. Warner Schaie has expanded the study of cognitive development into adulthood. Rather than being stable from adolescence, Schaie sees adults as progressing in the application of their cognitive abilities. 

Modern cognitive development has integrated the considerations of cognitive psychology and the psychology of individual differences into the interpretation and modeling of development. Specifically, the neo-Piagetian theories of cognitive development showed that the successive levels or stages of cognitive development are associated with increasing processing efficiency and working memory capacity. These increases explain progression to higher stages, and individual differences in such increases by same-age persons explain differences in cognitive performance. Other theories have moved away from Piagetian stage theories, and are influenced by accounts of domain-specific information processing, which posit that development is guided by innate evolutionarily-specified and content-specific information processing mechanisms.

Social and emotional development
Developmental psychologists who are interested in social development examine how individuals develop social and emotional competencies. For example, they study how children form friendships, how they understand and deal with emotions, and how identity develops. Research in this area may involve study of the relationship between cognition or cognitive development and social behavior.

Research methods
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 their development.

Research design
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. As an example a longitudinal study of early literacy development examined in detail the early literacy experiences of one child in each of 30 families. 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.

A third study design, the cohort 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. While much more resource-intensive, the format aids in a clearer distinction between what changes can be attributed to individual or historical environment from those which are truly universal.

Notably, 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 easily randomly assign certain families to a poverty condition and others to an affluent one, and so observation alone has to suffice.

Pre-natal development
Pre-natal development is of interest to psychologists investigating the context of early psychological development. For example, some primitive reflexes arise before birth and are still present in newborns. One hypothesis is that these reflexes are vestigial and have limited use in early human life. Piaget's theory of cognitive development suggested that some early reflexes are building blocks for infant sensorimotor development. For example the tonic neck reflex may help development by bringing objects into the infant's field of view. Other reflexes, such as the walking reflex appear to be replaced by more sophisticated voluntary control later in infancy. This may be because the infant gains too much weight after birth to be strong enough to use the reflex, or because the reflex and subsequent development are functionally different. It has also been suggested that some reflexes (for example the moro and walking reflexes) are predominantly adaptations to life in the womb with little connection to early infant development. Primitive reflexes reappear in adults under certain conditions, such as neurological conditions like dementia or traumatic lesions.

Ultrasound has shown that infants are capable of a range of movements in the womb, many of which appear to be more than simple reflexes. By the time they are born, infants can recognize and have a preference for their mother's voice suggesting some pre-natal development of auditory perception. Pre-natal development and birth complications may also be connected to neurodevelopmental disorders, for example in schizophrenia. With the advent of cognitive neuroscience, embryology and the neuroscience of pre-natal development is of increasing interest to developmental psychology research.

Infancy
From birth until the onset of speech, the child is referred to as an infant. Developmental psychologists vary widely in their assessment of infant psychology, and the influence the outside world has upon it, but certain aspects are relatively clear.

The majority of a newborn infant's time is spent in sleep. At first this sleep is evenly spread throughout the day and night, but after a couple of months, infants generally become diurnal.

Infants can be seen to have six states, grouped into pairs: Infants respond to stimuli differently in these different states.
 * quiet sleep and active sleep (dreaming, when REM sleep occurs)
 * quiet waking, and active waking
 * fussing and crying

Habituation (see above) has been used to discover the resolution of perceptual systems, suggesting that infants' basic perceptual abilities develop before acquisition of object permanence. An early theory of infant development was the Sensorimotor stage of Piaget's Theory of cognitive development. Piaget suggested that an infant's perception and understanding of the world depended on their motor development, which was required for the infant to link visual, tactile and motor representations of objects. According to this view, it is through touching and handling objects that infants develop object permanence, the understanding that objects are solid, permanent, and continue to exist when out of sight. Special methods are used to study infant behavior.Piaget's Sensorimotor Stage comprised six sub-stages (see sensorimotor stages for more detail). In the early stages, development arises out of movements caused by primitive reflexes. Discovery of new behaviors results from classical and operant conditioning, and the formation of habits. From eight months the infant is able to uncover a hidden object but will persevere when the object is moved. Piaget's evidence for an incomplete understanding of object permanence before 18 months was the infant's failure to look for an object where it was last seen. Instead infants continue to look for an object where it was first seen, committing the "A-not-B error."
 * Vision is significantly worse in infants than in older children. Infant sight, blurry in early stages, improves over time. Color perception similar to that seen in adults has been demonstrated in infants as young as four months, using habituation methods.<sup class="reference" id="cite_ref-butterworth_10-2">
 * Hearing is well-developed prior to birth, however, and a preference for the mother's 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 showing different expressions of disgust or pleasure when presented with pleasant odors (honey, milk, etc.) or unpleasant odors (rotten egg) and tastes (e.g. sour taste). There is good evidence for infants preferring the smell of their mother to that of others.
 * Language: infants of around six months can differentiate between phonemes in their own language, but not between similar phonemes in another language. At this stage infants also start to babble, producing phonemes.
 * Touch is one of the better-developed senses at birth, being one of the first to develop inside the womb. This is evidenced by the primitive reflexes described above, and the relatively advanced development of the somatosensory cortex.
 * Pain: Infants feel pain similarly, if not more strongly than older children but pain-relief in infants has not received so much attention as an area of research.<sup class="reference" id="cite_ref-MatthewMatthew_13-0">

Later researchers have developed a number of other tests which suggest that younger infants understand more about objects than first thought. These experiments usually involve a toy, and a crude barrier which is placed in front of the toy, and then removed, repeatedly. Before the age of eight to nine months, infants' inability to understand object permanence extends to people, which explains why infants at this age do not cry when their mothers are gone ("Out of sight, out of mind").

There are critical periods in infancy and childhood during which development of certain perceptual, sensorimotor, social and language systems depends crucially on environmental stimulation.<sup class="reference" id="cite_ref-Siegler_15-0"> Feral children such as Genie, deprived of adequate stimulation, fail to acquire important skills which they are then unable to learn in later childhood. The concept of critical periods is also well-established in neurophysiology, from the work of Hubel and Wiesel among others. Some feel that classical music, particularly Mozart is good for an infant's mind. While some tentative research has shown it to be helpful to older children, no conclusive evidence is available involving infants.<sup class="reference" id="cite_ref-16">

Babyhood
Intelligence is demonstrated through the use of symbols, language use matures, and memory and imagination are developed. Thinking is done in a non-logical, nonreversible manner. Egocentric thinking predominates.

Socially, toddlers are little people attempting to become independent at this stage, which they are commonly called the "terrible twos." They walk, talk, use the toilet, and get food for themselves. Self-control begins to develop. If taking the initiative to explore, experiment, risk mistakes in trying new things, and test their limits is encouraged by the caretaker(s) the child will become autonomous, self-reliant, and confident. If the caretaker is overprotective or disapproving of independent actions, the toddler may begin to doubt their abilities and feel ashamed for the desire for independence. The child's autonomic development will be inhibited, and be less prepared to successfully deal with the world in the future.

Early childhood
Also called "pre-school age," "exploratory age" and "toy age." When children attend preschool, they broaden their social horizons and become more engaged with those around them. Impulses are channeled into fantasies, which leaves the task of the caretaker to balance eagerness for pursuing adventure, creativity and self expression with the development of responsibility. If caretakers are properly encouraging and consistently disciplinary, children are more likely to develop positive self-esteem while becoming more responsible, and will follow through on assigned activities.If not allowed to decide which activities to perform, children may begin to feel guilt upon contemplating taking initiative.<sup class="Template-Fact" style="white-space:nowrap;"> This negative association with independence will lead them to let others make decisions in place of them.

Late childhood
In late childhood, intelligence is demonstrated through logical and systematic manipulation of symbols related to concrete objects. Operational thinking develops, which means actions are reversible, and egocentric thought diminishes.

Children go through the transition from the world at home to that of school and peers. Children learn to make things, use tools, and acquire the skills to be a worker and a potential provider. Children can now receive feedback from outsiders about their accomplishments. If children can discover pleasure in intellectual stimulation, being productive, seeking success, they will develop a sense of competence. If they are not successful or cannot discover pleasure in the process, they may develop a sense of inferiority and feelings of inadequacy that may haunt them throughout life. This is when children think of themselves as industrious or as inferior.

Adolescence
Adolescence is the period of life between the onset of puberty and the full commitment to an adult social role, such as worker, parent, and/or citizen. It is the period known for the formation of personal and social identity (see Erik Erikson) and the discovery of moral purpose (see William Damon). Intelligence is demonstrated through the logical use of symbols related to abstract concepts and formal reasoning. A return to egocentric thought often occurs early in the period. Only 35% develop the capacity to reason formally during adolescence or adulthood. (Huitt, W. and Hummel, J. January 1998)<sup class="reference" id="cite_ref-17">

It is divided into three parts namely: The adolescent unconsciously explores questions such as "Who am I? Who do I want to be?" Like toddlers, adolescents must explore, test limits, become autonomous, and commit to an identity, or sense of self. Different roles, behaviors and ideologies must be tried out to select an identity. Role confusion and inability to choose vocation can result from a failure to achieve a sense of identity through, for example, friends.
 * 1) Early Adolescence: 10 to 12 years (preteen, tween),
 * 2) Mid Adolescence: 13 to 15 years and
 * 3) Late Adolescence: 16 to 19 years

Early adulthood
The person must learn how to form intimate relationships, both in friendship and love. The development of this skill relies on the resolution of other stages. It may be hard to establish intimacy if one has not developed trust or a sense of identity. If this skill is not learned the alternative is alienation, isolation, a fear of commitment, and the inability to depend on others.

A related framework for studying this part of the life span is that of emerging adulthood, introduced in 2000 by Jeffrey Arnett. Scholars of emerging adulthood are interested not only in relationship development (focusing on the role of dating in helping individuals settle on a long-term spouse/partner), but also the development of sociopolitical views and occupational choice.

Middle age
Middle adulthood generally refers to the period between ages 40 to 60. During this period, the middle-aged experience a conflict between generativity and stagnation. They may either feel a sense of contributing to the next generation and their community or a sense of purposelessness.

Physically, the middle-aged experience a decline in muscular strength, reaction time, sensory keenness, and cardiac output. Also, women experience menopause and a sharp drop in the hormone estrogen. Men do have an equivalent to menopause, it is called andropause which is a hormone fluctuation with physical and psychological effects similar to menopause.

Old age
This stage generally refers to those over 60–80 years. During old age, people experience a conflict between integrity vs. despair. When reflecting on their life, they either feel a sense of accomplishment or failure.

Physically, older people experience a decline in muscular strength, reaction time, stamina, hearing, distance perception, and the sense of smell. They also are more susceptible to severe diseases such as cancer and pneumonia due to a weakened immune system. Mental disintegration may also occur, leading to dementia or Alzheimer's disease. However, partially due to a lifetime's accumulation of antibodies, the elderly are less likely to suffer from common diseases such as the cold.

Whether or not intellectual powers increase or decrease with age remains controversial. Longitudinal studies have suggested that intellect declines, while cross-sectional studies suggest that intellect is stable. It is generally believed that crystallized intelligence increases up to old age, while fluid intelligence decreases with age.

Parenting
In Western developed societies, mothers (and women generally) were emphasized to the exclusion of other caregivers, particularly as the traditional role of the father was more the breadwinner, and less the direct caregiver of an infant, he has been traditionally viewed as impacting an infant indirectly through interactions with the mother of the child.

''The emphasis of study has shifted to the primary caregiver (regardless of gender or biological relation), as well as all persons directly or indirectly influencing the child (the family system). The roles of the mother and father are more significant than first thought as we moved into the concept of primary caregiver.''

Affirming a role for fathers, studies have shown that children as young as 15 months benefit significantly from substantial engagement with their father. In particular, a study in the U.S. and New Zealand found the presence of the natural father was the most significant factor in reducing rates of early sexual activity and rates of teenage pregnancy in girls.<sup class="reference" id="cite_ref-20"> Covariate factors used included early conduct problems, maternal age at first childbirth, race, maternal education, father's occupational status, family living standards, family life stress, early mother–child interaction, measures of psychosocial adjustment and educational achievement, school qualifications, mood disorder, anxiety disorder, suicide attempts, violent offending, and conduct disorder. Further research has found fathers have an impact on child academic performance, including involved nonresident fathers.<sup class="reference" id="cite_ref-aredos_18-1"> However, father absence is associated with a range of negative outcomes for children, including child and later criminal behavior.

Historical antecedents
The modern form of developmental psychology has its roots in the rich psychological tradition represented by Aristotle, Tabari,<sup class="reference" id="cite_ref-Amber_22-0"> Rhazes,<sup class="reference" id="cite_ref-Tschanz_23-0"> 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-18th 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 19th 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.<sup class="reference" id="cite_ref-24"> By the early to mid-20th century, the work of Vygotsky and Piaget, mentioned above, had established a strong empirical tradition in the field.

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12th Oct 2011

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http://en.wikipedia.org/wiki/Developmental_psychology