User:Finereach/Developmental Psychology

'Developmental psychology', also known as human development, is the scientific study of systematic psychological changes that occur in human beings over the course of the life span. Originally concerned with infants and children, the field has expanded to include adolescence and 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.

Theorists and theories
Many theoretical perspectives attempt to explain development; among the most prominent are: Jean Piaget's Stage Theory, Lev Vygotsky's Social Contextualism (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.

Piagetian stages of cognitive development
Piaget was a French speaking Swiss theorist who posited that children learn through 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.


 * Jean Piaget: Theory of cognitive development, Genetic epistemology

Vygotsky's cultural-historical theory
Vygotsky was a theorist from the Soviet era, who posited that children learn through hands-on experience, as 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. 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.


 * Lev Vygotsky: Social contextualism; Zone of proximal development

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 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 close, intimate, emotionally meaningful relationships. Attachment is described as a biological system that evolved to ensure the survival of the infant. In Harry Harlow's classic study, attachment from baby to adult macaques was demonstrated to be as important, if not more than food. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. 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.

Nature/nurture
A significant question in developmental psychology, Nature versus nurture, concerns whether development results mostly from innate, genetic factors or environmental factors. Historically "nativists" argued that genetic factors predominantly drive psychological development, and "empiricists" argued for development driven by interaction with the environment. Today fewer developmental psychologists take these extreme positions, rather innate and environmental influences are among a number of factors investigated. One of the ways that this relationship has been explored more recently is through the emerging field of evolutionary developmental psychology.

A notable nature vs. nurture question is whether language acquisition, particularly of grammar, is genetic or acquired through learning. Linguist Noam Chomsky's universal grammar theory asserts that the structure of lanugage is far to complex for an infant to acquire given the little information in the language the infant hears. In this view there exists a special cognitive module suited for learning language, often called the language acquisition device. Other researchers suggest instead that language input provides sufficient information for statistical learningof language structure and that language can be acquired via general learning mechanisms underpinning other aspects of development, e.g. perceptual learning.

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.

Other developmental theories and theorists

 * Jerome Bruner: Cognitive (constructivist); learning theory / Narrative construction of reality
 * Erik Erikson: Erikson's stages of psychosocial development
 * Sigmund Freud: Psychosexual development
 * Lawrence Kohlberg: Kohlberg's stages of moral development
 * Judith Rich Harris: Modular theory of social 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.

Modern cognitive development has largely moved away from Piagetian stage theories, and is 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.

Methods and techniques
Designing psychological experiments for infants and children presents its own special challenges which developmental psychologists seek to address using specific experimental methods.

Techniques for studying infants

Psychologists often use the habituation methodology to assess infant ability. Typically, infants prefer stimuli that are novel relative to those they have encountered previously. Demonstrating a preference for one stimulus over another demonstrates that the infant can discriminate between them. Several methods are used to measure infants' preference. In the high-amplitude sucking procedure infants suck on a pacifier more or less depending on their level of interest. In other methods, infants kick their legs to indicate preference, or their level of interest is measured by the amount of time spent looking in a particular direction.

Habituation has been used to discover the resolution of perceptual systems by habituating an infant to a particular stimulus. If an infant is able to discriminate between an initial "habituated" stimulus and a novel stimulus, they will show a preference for the novel stimulus after habituation. More and more similar simuli are presented to determine the smallest degree of difference detectable by the infant.

Children

Methods are similar to those used to assess adults - for example, accuracy of responses, situational analysis etc. However false positives and false negatives may arise, because the child's lack of comprehension of the question may mask their true ability, or the task may be too superficial to demonstrate a lack of ability.

For example, accuracy of response has been used to assess ability on transitive inferences, conservation of number, counting, language tasks, theory of mind tasks and intelligence tests.

It has been argued that children's inability to achieve the conservation of number task, actually a lack of understanding of the question, which resulted in a false negative. Ainsworth came up with the naughty teddy task to attempt to make the test fairer on the child. However, creating such alternative tasks can itself result in further difficulties in interpreting results.

In considering development of an understanding of numbers, it is apparent that quite young children can be heard counting. However, deeper analysis of their numerical abilities shows that this counting relates only to a superficial level of understanding.

Adolescents

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.

Adults

Psychologists can use a wide range of different experimental methods with adults. Reaction times can be used to evaluate the extent to which age impacts on cognitive ability.

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. 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 resource 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 or cohort-sequential design 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 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 and many primitive reflexes also disappear in infancy. 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 (for example the tonic neck reflex) help infant sensori-motor development, bringing objects into the infant's field of view. . Other reflexes, such as the walking reflex disappear 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 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.

A range of movements have been seen in the womb using ultrasound, many of which appear to be more than simple reflexes. By the time they are born, infants can recognise and have a preference for their mother's voice. 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.

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 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 in these different states.

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.


 * Vision is significantly worse in infants than in older children. Infant sight, blurry in early stages, improves over time. Colour perception similar to that seen in adults has been demonstrated in infants as young as four months, using habituation methods.


 * 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 odours (honey, milk, etc) or unpleasant odours (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 from the medical profession.

There are critical periods in infancy and childhood during which development of certain perceptual, sensorimotor, social and language systems depends crucially on environmental stimulation. 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. There is also evidence of greater plasticity in infants and children, including some resilience to brain injury and greater ability to learn language at a young age. 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. .

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. .

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 behaviours 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 perservere when the object is moved. Piaget's evidence for a lack 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". Later researchers have developed a number of other tests which suggest that younger infants understand more about objects than first thought.

Toddler
Two to four years corresponds to the Symbolic function sub-stage of Piaget's pre-operational period. According to this theory Egocentric thinking and animism predominates, and thinking is done in a nonlogical, nonreversible manner. Intelligence is demonstrated through the use of symbols, language use matures, and memory and imagination are developed.

The following developmental activities are typically of interest to psychologists studying toddlers:
 * Speech: the first words are uttered. See language development
 * Development of imagination and pretend play
 * Motor development - for example learning to walk
 * Early but limited development of pre-math skills for example, in subitizing and learning to count.

Early childhood
4-7 years corresponds to the Intuitive thought substage of the Pre-operational stage of Piaget's Theory of cognitive development.

Topics of interest to developmental psychologists studying children in early childhood include:
 * Logical inferences, for example understanding syllogistic inferences, transitive inferences and conservation of number / volume
 * Acquisition of Theory of mind, the understanding that other people have thoughts and emotions different to one's own.
 * Language development including development speech production and comprehension, which starts at around one year, and learning to read and write later in childhood
 * Understanding number and mathematics
 * Development of morality
 * Drawing

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. This negative association with independence will lead them to let others make decisions in place of them.

Childhood
According to Piaget's Theory of cognitive development, from the age of around 12, intelligence is demonstrated through logical and systematic manipulation of symbols related to concrete objects. Piaget called this the Concrete Operational stage. 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)

The adolescent subconciously 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.

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 65. 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 not have an equivalent to menopause, but they do experience a decline in sperm count and speed of ejaculation and erection. Most men and women remain capable of sexual satisfaction after middle age.

Old age
This stage generally refers to those over 75 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.

Historical antecedents
The modern form of developmental psychology has its roots in the rich psychological tradition represented by Aristotle, Tabari, Rhazes, Alhazen, 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. By the early to mid-twentieth century, the work of Vygotsky and Piaget, mentioned above, had established a strong empirical tradition in the field.