Child development describes the formation of perceptual, emotional, intellectual and behavioral capabilities and functioning from a child's birth through puberty. The process involves the development of a person's sense of identity, language, empathy, symbolic thought, emotional awareness, logic, memory and morals. The development of a child is measured through different milestones related to social, physical and cognitive growth. Child development can be divided into three major stages in time: early childhood, middle childhood and adolescence. Each of the three stages includes different milestones to be achieved. It is impossible to set an exact boundary between any two as the process varies in each individual. Early childhood is considered the period from birth to approximately the age of eight. This stage is characterized by significant upsurge in all areas of development. Developing many foundation skills is seen as one of the primary milestones in early childhood. The period is important for the cognitive, social and emotional development of every individual. If children grow in an environment that cannot meet all their development needs, there is a risk that they may suffer some delays in learning and development. Huge physical changes appear during early childhood and they are often accompanied by the development of motor skills. Children learn to sit, walk, to use different toys and tools and they also learn to talk. Later they develop more advanced skills such as good control of pencils and scissors and even the ability to balance on one foot.
From birth children use all their senses to experience the environment. Throughout early childhood they start to develop a sense of cause and effect from the results of their actions. Rapid changes also occur in the children's cognitive and language development. During the first three years of life a child can develop a spoken vocabulary of up to a thousand words. Middle childhood is the period between eight and 12. In Sigmund Freud's psychoanalytic theory, this stage is described as the latent period. It is characterized by the repression of aggression and sexual urges. In more recent theory, however, middle childhood is considered an important period for the development of cognitive skills, personality, motivation and inter-personal relationships. Middle childhood is the time when children get familiar with the values of the society in which they are living. Integration is seen as the major development milestone of middle childhood. Puberty usually starts during the middle childhood phase. The on-set of puberty is usually earlier in females.
Adolescence is from around 12 years old to 18. It is characterized by accelerated growth. The key development milestone during adolescence is identity formation. Generally adolescence starts when individuals reach sexual maturity and concludes when they become adults. In some cultures, adolescence is rather short as reaching sexual maturity is perceived as turning into an adult. The case is quite different in the United States, where adolescence may extend until the early 20s. Sexual maturation differs in each individual and is also influenced by gender. Females usually mature earlier at the age of 13, while males reach sexual maturation around the age of 15. Most of the changes during adolescence are governed by the pituitary gland, which releases the hormone estrogen in females and the hormone testosterone in males. During adolescence there are also changes in the way an individual thinks and reasons about ideas or issues. Physical and cognitive growth is combined with the encountering of new people, situations and responsibilities. During this time there appears a conflict between one's identity and their role in society. Boys and girls distance themselves from their family and seek to get closer to their friends and equals. At the same time adolescence is considered the most crucial stage in growth in terms of emotional development. The period is usually characterized by mood swings that can be either a result of hormone surges or a logical reaction to all the changes that are happening. Struggle with self-esteem is also common for adolescents.