Child development

Child development involves the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence. Childhood is divided into 3 stages of life which include early childhood, middle childhood, and late childhood (preadolescence). Early childhood typically ranges from infancy to the age of 6 years old. During this period, development is significant, as many of life's milestones happen during this time period such as first words, learning to crawl, and learning to walk. There is speculation that middle childhood/preadolescence or ages 6–12 are the most crucial years of a child's life. Adolescence is the stage of life that typically starts around the major onset of puberty, with markers such as menarche and spermarche, typically occurring at 12–13 years of age. It has been defined as ages 10 to 19 by the World Health Organization. In the course of development, the individual human progresses from dependency to increasing autonomy. It is a continuous process with a predictable sequence, yet has a unique course for every child. It does not progress at the same rate and each stage is affected by the preceding developmental experiences. Because genetic factors and events during prenatal life may strongly influence developmental changes, genetics and prenatal development usually form a part of the study of child development. Related terms include developmental psychology, referring to development throughout the lifespan, and pediatrics, the branch of medicine relating to the care of children.

Developmental change may occur as a result of genetically controlled processes known as maturation, or as a result of environmental factors and learning, but most commonly involves an interaction between the two. It may also occur as a result of human nature and of human ability to learn from the environment.

There are various definitions of periods in a child's development, since each period is a continuum with individual differences regarding starting and ending. Some age-related development periods and examples of defined intervals include: newborn (ages 0–4 weeks); infant (ages 1 month–1 year); toddler (ages 1–2 years); preschooler (ages 2–6 years); school-aged child (ages 6–12 years); adolescent (ages 12–18 years).

Promoting child development through parental training, among other factors, promotes excellent rates of child development.
Parents play a large role in a child's activities, socialization, and development. Having multiple parents can add stability to a child's life and therefore encourage healthy development. Another influential factor in children's development is the quality of their care. Child-care programs may be beneficial for childhood development such as learning capabilities and social skills.

The optimal development of children is considered vital to society and it is important to understand the social, cognitive, emotional, and educational development of children. Increased research and interest in this field has resulted in new theories and strategies, with specific regard to practice that promotes development within the school system. Some theories seek to describe a sequence of states that compose child development.

Theories

Ecological systems

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 influential 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.

Piaget

Jean Piaget was a Swiss scholar who began his studies in intellectual development in the 1920s. Piaget's first interests were those that dealt with the ways in which animals adapt to their environments and his first scientific article about this subject was published when he was 10 years old. This eventually led him to pursue a Ph.D. in zoology, which then led him to his second interest in epistemology. Epistemology branches off from philosophy and deals with the origin of knowledge. Piaget believed the origin of knowledge came from Psychology, so he travelled to Paris and began working on the first "standardized intelligence test" at Alfred Binet laboratories; this influenced his career greatly. As he carried out this intelligence testing he began developing a profound interest in the way children's intellectualism works. As a result, he developed his own laboratory and spent years recording children's intellectual growth and attempted to find out how children develop through various stages of thinking. This led Piaget to develop four important stages of cognitive development: sensorimotor stage (birth to age 2), preoperational stage (age 2 to 7), concrete-operational stage (ages 7 to 12), and formal-operational stage (ages 11 to 12, and thereafter). Piaget concluded that adaption to an environment (behaviour) is managed through schemes and adaption occurs through ''assimilation'' and ''accommodation'

Stages

Sensorymotor: (birth to about age 2)

This is the first stage in Piaget's theory, where infants have the following basic senses: vision, hearing, and motor skills. In this stage, knowledge of the world is limited but is constantly developing due to the child's experiences and interactions. According to Piaget, when an infant reaches about 7–9 months of age they begin to develop what he called object permanence, this means the child now has the ability to understand that objects keep existing even when they cannot be seen. An example of this would be hiding the child's favorite toy under a blanket, although the child cannot physically see it they still know to look under the blanket.

Preoperational: (begins about the time the child starts to talk, about age 2)

During this stage of development, young children begin analyzing their environment using mental symbols. These symbols often include words and images and the child will begin to apply these various symbols in their everyday lives as they come across different objects, events, and situations. However, Piaget's main focus on this stage and the reason why he named it "preoperational" is because children at this point are not able to apply specific cognitive operations, such as mental math. In addition to symbolism, children start to engage in pretend play in which they pretend to be people they are not (teachers, superheroes). In addition, they sometimes use different props to make this pretend play more real. Some deficiencies in this stage of development are that children who are about 3–4 years old often display what is called egocentrism, which means the child is not able to see someone else's point of view, they feel as if every other person is experiencing the same events and feelings that they are experiencing. However, at about 7, thought processes of children are no longer egocentric and are more intuitive, meaning they now think about the way something looks instead of rational thinking.

Concrete: (about first grade to early adolescence)

During this stage, children between the age of 7 and 11 use appropriate logic to develop cognitive operations and begin applying this new thinking to different events they may encounter. Children in this stage incorporate inductive reasoning, which involves drawing conclusions from other observations in order to make a generalization. Unlike the preoperational stage, children can now change and rearrange mental images and symbols to form a logical thought, an example of this is reversibility in which the child now has the ability to reverse an action just by doing the opposite.

Formal operations: (about early adolescence to mid/late adolescence)

The final stage of Piaget's cognitive development defines a child as now having the ability to "think more rationally and systematically about abstract concepts and hypothetical events". Some positive aspects during this time is that child or adolescent begins forming their identity and begin understanding why people behave the way they behave. However, there are also some negative aspects which include the child or adolescent developing some egocentric thoughts which include the imaginary audience and the personal fable. An imaginary audience is when an adolescent feels that the world is just as concerned and judgemental of anything the adolescent does as they are; an adolescent may feel as if they are "on stage" and everyone is a critic and they are the ones being critiqued. A personal fable is when the adolescent feels that he or she is a unique person and everything they do is unique. They feel as if they are the only ones that have ever experienced what they are experiencing and that they are invincible and nothing bad will happen to them, it will only happen to others.

Vygotsky

Vygotsky was a Russian theorist, who proposed the sociocultural theory. During the 1920s–1930s while Piaget was developing his own theory, Vygotsky was an active scholar and at that time his theory was said to be "recent" because it was translated out of Russian language and began influencing Western thinking. He 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. An example of this might be when a parent "helps" an infant clap or roll her hands to the pat-a-cake rhyme, until she can clap and roll her hands herself.

Vygotsky was strongly focused on the role of culture in determining the child's pattern of development. He argued that "Every function in the child's cultural development appears twice: first, on the social level, and later, on the individual level; first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of concepts. All the higher functions originate as actual relationships between individuals."

Vygotsky felt that development was a process and saw periods of crisis in child development during which there was a qualitative transformation in the child's mental functioning.

Attachment

Attachment theory, originating in the work of John Bowlby and developed by Mary Ainsworth, is a psychological, evolutionary and ethological theory that provides a descriptive and explanatory framework for understanding interpersonal relationships between human beings. Bowlby's observations of close attachments led him to believe that close emotional bonds or "attachments" between an infant and their primary caregiver is an important requirement that is necessary to form "normal social and emotional development".

Erik Erikson

Erikson, a follower of Freud's, synthesized both Freud's and his own theories to create what is known as the "psychosocial" stages of human development, which span from birth to death, and focuses on "tasks" at each stage that must be accomplished to successfully navigate life's challenges.

Erikson's eight stages consist of the following:
*Trust vs. mistrust (infant)
*Autonomy vs. shame (toddlerhood)
*Initiative vs. guilt (preschooler)
*Industry vs. inferiority (young adolescent)
*Identity vs. role confusion (adolescent)
*Intimacy vs. isolation (young adulthood)
*Generativity vs. stagnation (middle adulthood)
*Ego integrity vs. despair (old age)

Behavioral

John B. Watson's behaviorism theory forms the foundation of the behavioral model of development 1925. Watson was able to explain the aspects of human psychology through the process of classical conditioning. With this process, Watson believed that all individual differences in behavior were due to different learning experiences. He wrote extensively on child development and conducted research (see Little Albert experiment). This experiment had shown that phobia could be created by classical conditioning. Watson was instrumental in the modification of William James' stream of consciousness approach to construct a stream of behavior theory. Watson also helped bring a natural science perspective to child psychology by introducing objective research methods based on observable and measurable behavior. Following Watson's lead, B.F. Skinner further extended this model to cover operant conditioning and verbal behavior. Skinner used the operant chamber, or Skinner box, to observe the behavior of small organisms in a controlled situation and proved that organisms' behaviors are influenced by the environment. Furthermore, he used reinforcement and punishment to shape in desired behavior.

Other

In accordance with his view that the sexual drive is a basic human motivation, Sigmund Freud developed
psychosexual theory of human development
from infancy onward, divided into five stages. Each stage centered around the gratification of the libido within a particular area, or erogenous zone, of the body. He also argued that as humans develop, they become fixated on different and specific objects through their stages of development. Each stage contains conflict which requires resolution to enable the child to develop.

The use of dynamical systems theory as a framework for the consideration of development began in the early 1990s and has continued into the present century. Dynamic systems theory stresses nonlinear connections (e.g., between earlier and later social assertiveness) and the capacity of a system to reorganize as a phase shift that is stage-like in nature. Another useful concept for developmentalists is the attractor state, a condition (such as teething or stranger anxiety) that helps to determine apparently unrelated behaviors as well as related ones. Dynamic systems theory has been applied extensively to the study of motor development; the theory also has strong associations with some of Bowlby's views about attachment systems. Dynamic systems theory also relates to the concept of the transactional process, a mutually interactive process in which children and parents simultaneously influence each other, producing developmental change in both over time.

The "core knowledge perspective" is an evolutionary theory in child development that proposes "infants begin life with innate, special-purpose knowledge systems referred to as core domains of thought" There are five core domains of thought, each of which is crucial for survival, which simultaneously prepare us to develop key aspects of early cognition; they are: physical, numerical, linguistic, psychological, and biological.

Continuity and discontinuity

Although the identification of developmental milestones is of interest to researchers and to children's caregivers, many aspects of developmental change are continuous and do not display noticeable milestones of change. Continuous developmental changes, like growth in stature, involve fairly gradual and predictable progress toward adult characteristics. When developmental change is discontinuous, however, researchers may identify not only milestones of development, but related age periods often called stages. A stage is a period of time, often associated with a known chronological age range, during which a behavior or physical characteristic is qualitatively different from what it is at other ages. When an age period is referred to as a stage, the term implies not only this qualitative difference, but also a predictable sequence of developmental events, such that each stage is both preceded and followed by specific other periods associated with characteristic behavioral or physical qualities.Gross, J. (1987). ''Introducing Erik Erikson''. Lanham, MD: University Press of America, .

Stages of development may overlap or be associated with specific other aspects of development, such as speech or movement. Even within a particular developmental area, transition into a stage may not mean that the previous stage is completely finished. For example, in Erikson's discussion of stages of personality, this theorist suggests that a lifetime is spent in reworking issues that were originally characteristic of a childhood stage. Similarly, the theorist of cognitive development, Piaget, described situations in which children could solve one type of problem using mature thinking skills, but could not accomplish this for less familiar problems, a phenomenon he called horizontal decalage.

Mechanisms

Although developmental change runs parallel with chronological age,Feldman, R. S. (2011). Development across the life span. 6th ed., Upper Saddle River, NJ: Prentice Hall, . age itself cannot cause development. The basic mechanisms or causes of developmental change are genetic factors and environmental factors. Genetic factors are responsible for cellular changes like overall growth, changes in proportion of body and brain parts, and the maturation of aspects of function such as vision and dietary needs. Because genes can be "turned off" and "turned on", the individual's initial genotype may change in function over time, giving rise to further developmental change. Environmental factors affecting development may include both diet and disease exposure, as well as social, emotional, and cognitive experiences. However, examination of environmental factors also shows that young human beings can survive within a fairly broad range of environmental experiences.

Rather than acting as independent mechanisms, genetic and environmental factors often interact to cause developmental change. Some aspects of child development are notable for their plasticity, or the extent to which the direction of development is guided by environmental factors as well as initiated by genetic factors. When an aspect of development is strongly affected by early experience, it is said to show a high degree of plasticity; when the genetic make-up is the primary cause of development, plasticity is said to be low. Plasticity may involve guidance by endogenous factors like hormones as well as by exogenous factors like infection.

One kind of environmental guidance of development has been described as experience-dependent plasticity, in which behavior is altered as a result of learning from the environment. Plasticity of this type can occur throughout the lifespan and may involve many kinds of behavior, including some emotional reactions. A second type of plasticity, experience-expectant plasticity, involves the strong effect of specific experiences during limited sensitive periods of development. For example, the coordinated use of the two eyes, and the experience of a single three-dimensional image rather than the two-dimensional images created by light in each eye, depend on experiences with vision during the second half of the first year of life. Experience-expectant plasticity works to fine-tune aspects of development that cannot proceed to optimum outcomes as a result of genetic factors working alone.

In addition to the existence of plasticity in some aspects of development, genetic-environmental correlations may function in several ways to determine the mature characteristics of the individual. Genetic-environmental correlations are circumstances in which genetic factors make certain experiences more likely to occur. For example, in passive genetic-environmental correlation, a child is likely to experience a particular environment because his or her parents' genetic make-up makes them likely to choose or create such an environment. In evocative genetic-environmental correlation, the child's genetically caused characteristics cause other people to respond in certain ways, providing a different environment than might occur for a genetically different child; for instance, a child with Down syndrome may be treated more protectively and less challengingly than a non-Down child. Finally, an active genetic-environmental correlation is one in which the child chooses experiences that in turn have their effect; for instance, a muscular, active child may choose after-school sports experiences that create increased athletic skills, but perhaps preclude music lessons. In all of these cases, it becomes difficult to know whether child characteristics were shaped by genetic factors, by experiences, or by a combination of the two.

Asynchronous development

Asynchronous development occurs in cases when a child's cognitive, physical, and/or emotional development occur at different rates. Asynchronous development is common for gifted children when their cognitive development outpaces their physical and/or emotional maturity, such as when a child is academically advanced and skipping school grade levels yet still cries over childish matters and/or still looks his or her age. Asynchronous development presents challenges for schools, parents, siblings, peers, and the children themselves, such as making it hard for the child to fit in or frustrating adults who have become accustomed to the child's advancement in other areas.

Research issues and methods

# What develops? What relevant aspects of the individual change over a period of time?
# What are the rate and speed of development?
# What are the mechanisms of development – what aspects of experience and heredity cause developmental change?
# Are there typical individual differences in the relevant developmental changes?
# Are there population differences in this aspect of development (for example, differences in the development of boys and of girls)?

Empirical research that attempts to answer these questions may follow a number of patterns. Initially, observational research in naturalistic conditions may be needed to develop a narrative describing and defining an aspect of developmental change, such as changes in reflex reactions in the first year. This type of work may be followed by correlational studies, collecting information about chronological age and some type of development such as vocabulary growth; correlational statistics can be used to state change. Such studies examine the characteristics of children at different ages. These methods may involve longitudinal studies, in which a group of children is re-examined on a number of occasions as they get older, or cross-sectional studies, in which groups of children of different ages are tested once and compared with each other, or there may be a combination of these approaches. Some child development studies examine the effects of experience or heredity by comparing characteristics of different groups of children in a necessarily non-randomized design. Other studies can use randomized designs to compare outcomes for groups of children who receive different interventions or educational treatments.

Infant research methods

When conducting psychological research on infants and children, there are certain key aspects of infants that need to be considered before embarking on research. Five key challenges to conducting research with infants are that infants cannot talk, have a limited behavioral repertoire, cannot follow instructions, have a short attention span, and develop rapidly (so methods need to be updated at different ages and developmental stages).

High-amplitude sucking technique (HAS) is one common way to explore infants' preferences. HAS is appropriate for infants from the time that they are born until they are four months old since it takes advantage of infants' sucking reflex. When this is a measure of interest, researchers will code a baseline sucking rate for each baby before exposing them to the item of interest. A common finding of HAS shows a relaxed, natural sucking rate when exposed to something the infant is familiar with, like their mother's voice, compared to an increased sucking rate around novel stimuli.

The preferential-looking techique was a breakthrough made by Robert L. Fantz in 1961. In his experiments, he would show the infants in his study two different stimuli. If an infant looks at one image longer than the other, there are two things that can be inferred: the infant can see that they are two different images and that the infant is showing preference to one image in some capacity. Depending on the goal of the experiment, infants may prefer to look at the novel and more interesting stimulus or they may look at the more comforting and familiar image.

Eye tracking is a straightforward way of looking at infants' preferences. One example of eye tracking, using an eye tracking software, it is possible to see if infants understand commonly used nouns by tracking their eyes after they are cued with the target word.
Another unique way to study infants' cognition is through habituation, which is the process of repeatedly showing a stimulus to an infant until they give no response. Then, when infants are presented with a novel stimulus, they show a response. This violation of expectation reveals patterns of cognition and perception. Using this study method, many different cognitive and perceptual ideas can be studied. Looking time is a common measure of habituation. Looking time is studied by recording how long an infant looks at a stimulus until they are habituated to that stimulus. Then, researchers record if an infant becomes dishabituated to a novel stimulus. This method can be used to measure preferences infants, including aesthetic preferences for certain colors. Additionally, other discriminatory tasks can be studied, including auditory discrimination between different musical excerpts.

Another way that children are studied is through brain imaging technology. One example used a lot in child development studies is Magnetic Resonance Imaging (MRI). These machines can be used to track brain activity, growth, and connectivity in children Brain development can be tracked from when a child is a fetus with this new technology. Another common type of brain imaging can be collected with electroencephalography (EEG). This technology can be used to diagnose seizures and encephalopathy, but considering conceptual age of the infant is important for analyzing the results.

Ethical considerations

Most of the ethical challenges that exist in studies with adults exist within children. However, there are some notable differences in ethical research that should be addressed when designing studies for children. An important consideration is that children should give their consent to participate in research. Because of the inherent power structure in most research settings, researchers must consider study designs that protect children from feeling coerced. Children are not allowed to give consent, so parents must give their informed consent for children to participate in research. Children can give their assent, which should be reliably checked by both verbal and nonverbal cues throughout their participation.

Milestones

Milestones are changes in specific physical and mental abilities (such as walking and understanding language) that mark the end of one developmental period and the beginning of another. For stage theories, milestones indicate a stage transition. Studies of the accomplishment of many developmental tasks have established typical chronological ages associated with developmental milestones. However, there is considerable variation in the achievement of milestones, even between children with developmental trajectories within the typical range. Some milestones are more variable than others; for example, receptive speech indicators do not show much variation among children with typical hearing, but expressive speech milestones can be quite variable.

A common concern in child development is developmental delay involving a delay in an age-specific ability for important developmental milestones. Prevention of and early intervention in developmental delay are significant topics in the study of child development. Developmental delays should be diagnosed by comparison with characteristic variability of a milestone, not with respect to average age at achievement. An example of a milestone would be eye-hand coordination, which includes a child's increasing ability to manipulate objects in a coordinated manner.

There is a phenomenal growth or exponential increase of child development from the age of 4 to 15 years old especially during the age of 4 to 7 years old based on the Yamana chart 06.03.13 Minister Fitzgerald's Statement in Seanad on Early Years Strategy and the Economic Benefits of Early Intervention - Department of Children and Youth Affairs - Ireland
. Dcya.gov.ie (2013-03-06). Retrieved on 2016-10-31.). The Heckman's chart shows that the highest return of investment in education is maximum during the early years (age 1 to 3 years old) and decreases to a plateau during the school-aged years and adolescence. There are various child development tables or charts e.g. the PILES table where PILES stands for Physical, Intellectual, Language, Emotional and Social development aspects.

Aspects

Child development is not a matter of a single topic, but progresses somewhat differently for different aspects of the individual. Here are descriptions of the development of a number of physical and mental characteristics.

Physical growth

Physical growth in stature and weight occurs over the 15–20 years following birth, as the individual changes from the average weight of 3.5 kg and length of 50 cm at full term birth to full adult size. As stature and weight increase, the individual's proportions also change, from the relatively large head and small torso and limbs of the neonate, to the adult's relatively small head and long torso and limbs. The child's pattern of growth is in a head-to-toe direction, or cephalocaudal, and in an inward to outward pattern (center of the body to the peripheral) called proximodistal.

Speed and pattern

The speed of physical growth is rapid in the months after birth, then slows, so birth weight is doubled in the first four months, tripled by age 12 months, but not quadrupled until 24 months. Growth then proceeds at a slow rate until shortly before puberty (between
about 9 and 15 years of age), when a period of rapid growth occurs.
Growth is not uniform in rate and timing across all body parts. At birth, head size is already relatively near to that of an adult, but the lower parts of the body are much smaller than adult size. In the course of development, then, the head grows relatively little, and torso and limbs undergo a great deal of growth.

Mechanisms of change

Genetic factors play a major role in determining the growth rate, and particularly the changes in proportion characteristic of early human development. However, genetic factors can produce maximum growth only if environmental conditions are adequate. Poor nutrition and frequent injury and disease can reduce the individual's adult stature, but the best environment cannot cause growth to a greater stature than is determined by heredity.

Individual variation versus disease

Individual differences in height and weight during childhood are considerable. Some of these differences are due to family genetic factors, others to environmental factors, but at some points in development they may be strongly influenced by individual differences in reproductive maturation.

The American Association of Clinical Endocrinologists defines short stature as height more than 2 standard deviations below the mean for age and gender, which corresponds to the shortest 2.3% of individuals. In contrast, failure to thrive is usually defined in terms of weight, and can be evaluated either by a low weight for the child's age, or by a low rate of increase in the weight. A similar term, stunted growth, generally refers to reduced growth rate as a manifestation of m