Developmental psychology is the scientific study of 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.
Attachment theory 
Attachment theory, theoretical frame work 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.
There are three types of attachment styles: secure, anxious-avoidant, and anxious-resistant. Secure attachment is a healthy attachment between the infant and the caregiver. It is characterized by trust. Anxious-avoidant is an insecure attachment between an infant and a caregiver. This is characterized by the infant's indifference toward the caregiver. Anxious-resistant is an insecure attachment between the infant and the caregiver characterized by distress from the infant when separated and anger when reunited.
A child can be hindered in its natural tendency to form 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.
Constructivism is a paradigm in psychology that characterizes learning as a process of actively constructing knowledge. Individuals create meaning for themselves or make sense of new information by selecting, organizing, and integrating information with other knowledge, often in the content of social interactions. There are two ways in which constructivism can occur: individual and social. Individual constructivism is when a person constructs knowledge through cognitive processes of their own experiences rather than by memorizing facts provided by others. Social constructivism is when individuals construct knowledge through an interaction between the knowledge they bring to a situation and social or cultural exchanges within that content.
Ecological systems theory 
The 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.
The microsystem is the immediate environment surrounding as individual. The mesosystem is the combination of two microsystems. The exosystem is the interaction among two or more environments. The macrosystem is broader taking into account social economic status, culture, beliefs, customs and morals. Lastly, the chronosystem refers to the chronological nature of development.[clarification needed]
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.
Psychosexual development 
Sigmund Freud believed that we all had a conscious, preconscious, and unconscious level. In the conscious we are aware of our mental process. The preconscious involves information that though we are not currently thinking about can be brought into consciousness. Lastly, the unconscious includes those mental processes which we are unaware of. He believed that the conscious and unconscious had tension because the conscious would try and hold back what the unconscious was trying to express. To explain this he developed three structures of personality; the id, ego, and superego. The id, being the most primitive of the three functioned according to the pleasure principle. The pleasure principle states that the id’s motivation is to seek pleasure and avoid pain. Based on this he proposed five universal stages of development. The first is the oral stage which occurs from birth to 12 months of age, second is the anal stage which occurs from one to three years of age, third is the phallic stage which occurs from three to five years of age (most of a person’s personality is formed by this age), the fourth is called latency which occurs from age five until puberty, and lastly stage five is the genital stage which takes place from puberty until adulthood.
Stages of moral development 
Theories of morality that stem from Jean Piaget’s cognitive-developmental viewpoint emphasize shifts in the type of reasoning that individuals use in making moral decisions. Changes in the content of the decision they reach or the actions they take as a result does not occur.[dubious ] Lawrence Kohlberg expanded on this issue specifically during adolescence. He suggested three levels of moral reasoning; preconventional moral reasoning, conventional moral reasoning, and postconventional moral reasoning. Preconventional moral reasoning is typical of children and is characterized by reasoning that is based on rewards and punishments associated with different courses of action. Conventional moral reason occurs during late childhood and early adolescence and is characterized by reasoning that is based on the rules and conventions of society. Lastly, postconventional moral reasoning is the stage during which society’s rules and conventions are seen as relative and subjective rather than as authoritative.
Erik Erikson became a child psychoanalyst like his mentor Anna Freud, Sigmond Freud’s daughter. He went on to reinterpret Freud’s psychosexual stages by incorporating the social aspects of it. He came up with eight stages, each of which has two crisis (a positive and a negative). Stage one is trust versus mistrust, which occurs during infancy. Stage two is autonomy versus shame and doubt which occurs during early childhood. Stage three is initiative versus guilt which occurs during play age. Stage four is industry versus inferiority which occurs during school age. Stage five is identity versus identity diffusion which occurs during adolescence. Stage six is intimacy versus isolation which occurs during young adulthood. Stage seven is generativity versus self-absorption which occurs during adulthood. Lastly, stage eight is integrity versus despair which occurs during old age. In each of these stages either one or the other crisis is developed. The ideal thing would be to have the positive crisis more developed than the negative crisis.
Theories of cognitive development 
Jean Piaget was a 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.
Piaget believed that intellectual development took place through a series of stages which caused him to come up with his Theory on Cognitive Development. Each stage consisted of steps which the child had to master before moving on to the next step. He believe that these stages where not separate from one another but rather each stage built on the previous one, hence learning was continuous. His theory consisted of four stages; sensorimotor, pre-operational, concrete operational, and formal operational. Though he did not believe these stages occurred at any given age, many studies have determine when these cognitive abilities should take place.
Zone of proximal development 
Lev Vygotsky was a Russian theorist from the Soviet era, who posited that children learn through hands-on experience and social interactions with members of his/her culture. 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. In other words, Vygotsky claimed that psychology should focus on the progress of human consciousness through the relationship of an individual and their environment. He felt that if scholars continued to disregard this connection, then this disregard would inhibit the full comprehension of the human consciousness.
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 polarised 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.
Research areas 
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. In addition, children in higher-levels of cognitive development have been observed to have greater mathematical fluency in basic addition and subtraction problems. These increases explain differences between stages, progression to higher stages, and individual differences of children who are the same-age and of the same grade-level. However, 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.
Erik Erikson believed we undergo several stages to achieve social and emotional development. These stages were called the Erik Erikson's Stages of Psychosocial Development. The stages were trust vs. mistrust, attachment, parenting style, ego identity, role diffusion, generativity versus stagnation, midlife crisis, and ego integrity versus despair.
Emotional regulation or ER refers to an individual's ability to modulate emotional responses across a variety of contexts. In young children, this modulation is in part controlled externally, by parents and other authority figures. As children develop, they take on more and more responsibility for their internal state. Studies have shown that the development of ER is affected by the emotional regulation children observe in parents and caretakers, the emotional climate in the home, and the reaction of parents and caretakers to the child's emotions.
Physical development 
Physical development concerns the physical maturation of an individual's body until it reaches the adult stature. Although physical growth is a highly regular process, all children differ tremendously in the timing of their growth spurts. Studies are being done to analyze how the differences in these timings affect and are related to other variables of developmental psychology such as information processing speed. Traditional measures of physical maturity using x-rays are less in practice nowadays, compared to simple measurements of body parts such as height, weight, head circumference, and arm span.
A few other studies and practices with physical developmental psychology are the phonological abilities of mature 5- to 11-year-olds, and the controversial hypotheses of left-handers being maturationally delayed compared to right-handers. A study by Eaton, Chipperfield, Ritchot, and Kostiuk in 1996 found in three different samples that there was no difference between right- and left-handers.
Memory development 
Researchers interested in memory development look at the way our memory develops from childhood and onward. According to Fuzzy-trace theory, we have two separate memory processes: verbatim and gist. These two traces begin to develop at different times as well as at a different pace. Children as young as 4 years-old have verbatim memory, memory for surface information, which increases up to early adulthood, at which point it begins to decline. On the other hand, our capacity for gist memory, memory for semantic information, increases up to early adulthood, at which point it consistent through old age. Furthermore, our reliance on gist memory traces in reasoning increases as we age.
Research methods and designs 
Main research methods 
Developmental psychology employs many of the research methods used in other areas of psychology. However, infants and children cannot be tested in the same ways as adults, so different methods are often used to study their development. Developmental psychologists have a number of methods to study changes in individuals over time. Common research methods include systematic observation, including naturalistic observations or structured observations; self-reports, which could be clinical interviews or structured interviews; clinical or case study method; and ethnography or participant observation.:31-35These methods differ in the extent to which researchers impose control over the conditions of the study and how they have constructed ideas about which variables to be studied. Every developmental investigation can be characterized in terms of whether its underlying strategy involves the experimental, correlational, or case study approach. The experimental method involves "actual manipulation of various treatments, circumstances, or events to which the participant or subject is exposed; the experimental design points to cause-and-effect relationships. This method allows for strong inferences to be made of causal relationships between the manipulation of one or more independent variables and subsequent behavior, as measured by the dependent variable. The advantage of using this research method is that it permits determination of cause-and-effect relationships among variables. On the other hand, the limitation is that data obtained in an artificial environment may lack generalizability. The correlational method explores the relationship between two or more events by gathering information about these variables without researcher intervention. The advantage of using a correlational design is that it estimates the strength and direction of relationships among variables in the natural environment; however, the limitation is that it does not permit determination of cause-and-effect relationships among variables. The case study approach allows investigations to obtain an in-depth understanding of an individual participant by collecting data based on interviews, structured questionnaires, observations, and test scores. Each of these methods have its strengths and weaknesses but the experimental method when appropriate is the preferred method of developmental scientists because it provides a controlled situation and conclusions to be drawn about cause-and-effect relationships.
Research designs 
Most developmental studies, regardless of whether they employ the experimental, correlational, or case study method, can also be constructed using research designs. Research designs are logical frameworks used to make key comparisons within research studies such as:
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.:40
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 event.:41
A third study design, the 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. 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.:42
Because every method has some weaknesses, developmental psychologists rarely rely on one study or even one method to reach conclusions by finding consistent evidence from as many converging sources as possible.
Life stages of psychological development 
Pre-natal development 
Pre-natal development is of interest to psychologists investigating the context of early psychological development. The whole prenatal development involves three main stages: germinal stage, embryonic stage and fetal stage. Germinal stage begins at conception until 2 weeks; embryonic stage means the development from 2 weeks to 8 weeks; fetal stage represents 9 weeks until birth of the baby. The senses develop in the womb itself: a fetus can both see and hear by the second trimester (13 to 24 weeks of age). Sense of touch develops in the embryonic stage (5 to 8 weeks).:97 Most of the brain's billions of neurons also are developed by the second trimester.:100 Babies are hence born with some odor, taste and sound preferences, largely related to the mother's environment.:101
Some primitive reflexes too 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.
Several environment agents—teratogens—can cause damage during the prenatal period. These include prescription and nonprescription drugs, illegal drugs, tobacco, alcohol, environmental pollutants, infectious disease agents such as the rubella virus and the toxoplasmosis bacterium, maternal malnutrition, maternal emotional stress, and Rh factor blood incompatibility between mother and child.:102-115
From birth until the first year, 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.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, from the work of Hubel and Wiesel among others.Babies are born with the ability to discriminate virtually all sounds of all human languages.:189 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.
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:
- quiet sleep and active sleep (dreaming, when REM sleep occurs)
- quiet waking, and active waking
- fussing and crying
Infant Perception: Infant perception is what a newborn can see, hear, smell, taste, and touch. These five features are better known as ones “five senses”. Infants respond to stimuli differently in these different states.
- Vision is significantly worse in infants than in older children. Infant sight tends to be blurry in early stages but improves over time. Color perception similar to that seen in adults has been demonstrated in infants as young as four months, using habituation methods. Infants get to adult-like vision in about six months.:191
- Hearing is well-developed prior to birth, unlike vision. Newborns prefer complex sounds to pure tones, human speech to other sounds, mother's voice to other voices, and the native language to other languages. Scientist believe these features are probably learned in the womb.:151 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). Newborns are born with odor and taste preferences acquired in the womb from the smell and taste of amniotic fluid, in turn influenced by what the mother eats. Both breast- and bottle-fed babies around 3 days old prefer the smell of human milk to that of formula, indicating an innate preference.:150 There is good evidence for older infants preferring the smell of their mother to that of others.
- Touch and feel is one of the better-developed senses at birth considering it's one of the first senses 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.
Infant Cognition: The Piagetian Era 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 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 came to his conclusion that infants lacked a complete understanding of object permanence before 18 months after observing infants' failure before this age 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." Some researchers have suggested that 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").
Recent Finding in Infant Cognition In the 1980s and 1990s, researchers have developed many new methods of assessing infants' understanding of the world with far more precision and subtlety than Piaget was able to do in his time. Since then, many studies based on these methods suggest that young infants understand far more about the world than first thought.
Based on recent findings, some researchers (such as Elizabeth Spelke and Renee Baillargeon) have proposed that an understanding of object permanence is not learned at all, but rather comprises part of the innate cognitive capacities of our species.
Other research has suggested that young infants in their first six months of life may possess an understanding of numerous aspects of the world around them, including:
- an ability to infer the goals of people in their environment;
- an ability to engage in simple causal reasoning.
Critical Periods of Development 
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, from the work of Hubel and Wiesel among others.
Infants shift between ages of one and two to a developmental stage known as toddlerhood. In this stage, an infant’s transition into toddlerhood is highlighted through self-awareness, developing maturity in language use, and presence of memory and imagination.
During toddlerhood, babies begin learning how to walk, talk, and make decisions for themselves. An important characteristic of this age period is the development of language, where children are learning how to communicate and express their emotions and desires through the use of vocal sounds, babbling, and eventually words. Self-control also begins to develop. At this age, children take initiative to explore, experiment, and learn from making mistakes. Allowing toddlers to try new things and test their limit is encouraged by caretakers in order to allow the child to 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. Toddlers also begin to identify themselves to gender roles, acting according to their perception of what a man or woman should do.
Socially, the period of toddlerhood is commonly called the "terrible twos". Toddlers often use their new-found language abilities to voice their desires, but are often misunderstood by parents due to their language skills just beginning to develop. A person at this stage testing their independence is another reason behind the stage’s infamous label. Tantrums in a fit of frustration are also common.
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.
As children grow their past experiences will shape who they are, allow them to perceive the world in their own way. It helps a person go through everyday life. (Psychology: The Science of Behaviour, Fourth Canadian Edition by Neil R. Carlson, William Buskist, C. Donald Heth, and Rod Schmaltz). 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.
During a child's preschool and beginning school years, 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 their activities, including their intellectual stimulation, most importantly in learning reading, writing, and basic math, 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 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)
It is divided into three parts namely:
- Early Adolescence: 11 to 12 years (preteen, tween),
- Mid Adolescence: 13 to 15 years and
- Late Adolescence: 16 to 19 years
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.
Early adulthood 
Early adulthood, according to theorists such as Erik Erikson, is a stage where development is mainly focused on maintaining relationships. Examples include creating bond of intimacy, sustaining friendships, and ultimately making a family. Some theorists state that development of intimacy skills rely on the resolution of previous developmental stages. A sense of identity gained in the previous stages is also necessary for intimacy to develop. 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. Scholars of emerging adulthood, such as Jeffrey Arnett, are not necessarily interested in relationship development. Instead, this concept suggests that people transition after their teenage years into a period not characterized as relationship building and an overall sense of constancy with life, but with years of living with parents, phases of self-discovery, and experimentation.
Middle adulthood 
Middle adulthood generally refers to the period between ages 40 to 60. During this period, middle-aged adults experience a conflict between generativity and stagnation. They may either feel a sense of contributing to society, the next generation or their immediate 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 experience an equivalent endocrine system event to menopause. Andropause in males is a hormone fluctuation with physical and psychological effects that can be similar to those seen in menopausal females. As men age, lowered testosterone levels can contribute to mood swings and a decline in sperm count. Sexual responsiveness can also be affected, including delays in erection and longer periods of penile stimulation required to achieve ejaculation.
Old age 
This stage generally refers to those over 60–100 years. According to Erikson's Theory of Psychosocial Development, old age is the stage in which individuals assess the quality of their lives. In reflecting on their lives, people in this age group develop a feeling of integrity if deciding that their lives were successful or a feeling of despair if evaluation of one's life indicates a failure to achieve goals.
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 ailments such as Alzheimer's disease. Factors such as physical therapy and exercise have been identified as potential modulators of physical decline.
Because of a lifetime's accumulation of antibodies (among other factors), some of the elderly are less likely to suffer from certain ordinary diseases such as the common cold.
Expression [|sexuality in older age|] depends in large part upon the emotional and physical health of the individual. Many older adults continue to be sexually active and satisfied with their sexual activity.
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.
Other findings 
Parenting on Child Development 
Parenting variables alone have typically accounted for 20 to 50 percent of the variance in child outcomes. Depending on a parent’s care giving style, children can develop different forms of attachment. Attachments have been identified and categorized using the Strange Situation Procedure (SSP), in which researchers monitor infant’s reactions after his or her mother and stranger leave and reenter a room. The infant’s response, particularly to the mother finally reentering the room, is important in determining the type of attachment the baby feels to his or her caregiver. Four attachment theories have developed from this procedure: secure attachment, anxious-avoidant attachment, anxious-resistant attachment, and disorganized-disoriented attachment.
- Secure attachment is characterized by those children who seek attention from their mothers, are stressed when their mother leaves, and consoled when the mother returns.
- Anxious-avoidant children appear securely attached at the onset, but are not affected by the mother’s departure, and may avoid her when she returns.
- Anxious resistant children are significantly distressed by the mother’s departure, but are not consoled by her return.
- Disorganized-disoriented children show unpredictable patterns of behavior throughout the experiment.
Mothers who are attentive to their infants, and able to understand their wants and needs provide the environment for a child to develop a secure attachment. Conversely, maternal depression and stress can have adverse effects on attachment.
Parenting Styles 
The following parenting styles have been described in the child development literature:
Authoritative Parenting is characterized as those parents who have high parental warmth, responsiveness, and demandingness, but rate low in negativity and conflict. These parents are assertive but not intrusive or overly restrictive. This method of parenting is associated with more positive social and academic outcomes. Interestingly, the beneficial outcomes of authoritative parenting are not necessarily universal. Among African American adolescents, authoritative parenting is not associated with academic achievement without peer support for achievement.
Authoritarian parenting is characterized by low levels of warmth and responsiveness with high levels of demandingness and firm control. These parents focus on obedience and they monitor their children regularly. In general, this style of parenting is associated with maladaptive outcomes. Interestingly, the outcomes are more harmful for middle class boys than girls, preschool white girls than preschool black girls, and for white boys than Hispanic boys. Furthermore, the negative effects of authoritarian parenting among Asian Americans can be offset by positive peer support. Finally, among African Americans, some elements of authoritarian parenting such as firm control and physical discipline do not serve as predictive factors for negative outcomes.
Permissive parenting is characterized by high levels of responsiveness combined with low levels of demandingness. These parents are lenient and do not necessarily require mature behavior. They allow for a high degree of self regulation and typically avoid confrontation. Compared to children raised using the authoritative style, preschool girls raised in permissive families are less assertive. Additionally, preschool children of both sexes are less cognitively competent than those children raised under authoritative parenting styles.
Rejecting or neglectful parenting is the final category. This is characterized by low levels of demandingness and responsiveness. These parents are typically disengaged in their child’s lives, lacking structure in their parenting styles and are unsupportive. Children in this category are typically the least competent of all the categories.
Mother and Father Factors 
Parenting roles in child development have typically focused on the role of the mother. Recent literature, however, has looked toward the father as having an important role in child development. 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. Furthermore, another argument is that neither a mother nor a father is actually essential in successful parenting, and that single parents as well as homosexual couples can support positive child outcomes. According to this set of research, children need at least one consistently responsible adult with whom the child can have a positive emotional connection. Having more than one of these figures contributes to a higher likelihood of positive child outcomes.
Another parental factor often debated in terms of its effects on child development is divorce. Divorce in itself is not a determining factor of negative child outcomes. In fact, the majority of children from divorcing families fall into the normal range on measures of psychological and cognitive functioning. A number of mediating factors play a role in determining the effects divorce has on a child, for example, divorcing families with young children often face harsher consequences in terms of demographic, social, and economic changes than do families with older children. Positive coparenting after divorce is part of a pattern associated with positive child coping, while hostile parenting behaviors lead to a destructive pattern leaving children at risk. Additionally, direct parental relationship with the child also affects the development of a child after a divorce. Overall, protective factors facilitating positive child development after a divorce are maternal warmth, positive father-child relationship, and cooperation between parents.
Historical antecedents 
John Locke and Jean-Jacques Rousseau are typically cited as providing the foundations of modern form of developmental psychology.:9. 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;:10 prominent here was the pioneering psychologist G. Stanley Hall:10, who attempted to correlate ages of childhood with previous ages of mankind. 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. Baldwin was heavily involved in the theory of developmental psychology.:10 Sigmund Freud, whose concepts were developmental, had a significant impact on public perceptions.:10
See also 
- Behavioral cusp
- Child development
- Developmental psychobiology
- Developmental psychopathology
- Developmental Science (peer-reviewed journal)
- Evolutionary developmental psychopathology
- Ethnic identity development
- Fuzzy-trace theory
- Microgenetic design
- Ontogenetic parade
- Outline of psychology
- Perceptual narrowing
- Pre- and perinatal psychology
- Scale error
- Sociometric status
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Further reading 
- Bjorklund, D.F.; Pellegrini, A.D. (2000). "Child Development and Evolutionary Psychology". Child Development 71 (6): 1687–1708.
- Bornstein, M.H. & Lamb, M.E. (2005). Developmental science: An advanced textbook. Mahwah, NJ: Erlbaum, 2005.
- Johnson-Pynn, J.; Fragaszy, D.M. & Cummins-Sebree, S. (2003). "Common territories in comparative and developmental psychology: The quest for shared means and meaning in behavioral investigations.". International Journal of Comparative Psychology 16: 1–27.
- Lerner, R.M. Concepts and theories of human development. Mahwah, NJ: Erlbaum, 2002.
- Reid, V.; Striano, T. & Koops, W. Social Cognition During infancy. Psychology Press. 2007
- The Society for Research in Child Development
- The British Psychological Society, Developmental Psychology Section
- Developmental Psychology: lessons for teaching and learning developmental psychology
- GMU’s On-Line Resources for Developmental Psychology: a web directory of developmental psychology organizations
- Home Economics Archive: Research, Tradition, History (HEARTH)
An e-book collection of over 1,000 books spanning 1850 to 1950, created by Cornell University's Mann Library. Includes several hundred works on human development, child raising, and family studies itemized in a specific bibliography.
- Infants can do more than we think. Research from Uppsala university 2010.
- It's the Parenting, Dodo | Living Hero Radio Show and Podcast special. With Arun Gandhi telling 4 stories of growing up with Mahatma Gandhi's non-violent parenting and childhood development practices and Dr. Marcy Axness, author of Parenting for Peace giving parenting guidelines and information. Jan 2013