Child development refers to the biological and psychological and emotional changes that occur in human beings between birth and the end of adolescence, as the individual progresses from dependency to increasing autonomy. Because these developmental changes may be strongly influenced by genetic factors and events during prenatal life, genetics and prenatal development are usually included as 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 our ability to learn from our environment. Human beings have a keen sense to adapt to their surroundings and this is what child development encompasses.
There are various definitions of periods in a child's development, since each period is a continuum with individual differences regarding start and ending.
Some age-related development periods and examples of defined intervals are: newborn (ages 0–1 month); infant (ages 1 month – 1 year); toddler (ages 1–3 years); preschooler (ages 4–6years); school-aged child (ages 6–13 years); adolescent (ages 13–20). However, organizations like Zero to Three and the World Association for Infant Mental Health use the term infant as a broad category, including children from birth to age 3.
The optimal development of children is considered vital to society and so 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. In addition there are also some theories that seek to describe a sequence of states that compose child development.
Vygotsky was a theorist who worked during the first decades of the former Soviet Union. 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."