From the moment of birth, babies grow and develop physically, mentally, and socially. In the first year, a baby grows faster than at any other time in later life. Within the first few years, children learn basic skills and go on to acquire a wide range of physical and intellectual accomplishments.
Children pass through predictable patterns of growth and development, but each child progresses at a different rate. Physical growth and intellectual development are partly determined by genetic factors, but these processes are also affected by general health and stimulation from the environment.
Babies are born with various primitive reflexes: they communicate by crying and instinctively suck when offered a nipple. At first, babies grow fast, tripling in weight and growing in length by about 25 cm (10 in) in the first year. After about the age of 2, children begin a long, slower period of growth, which allows time for complex skills to be acquired.
A child’s intellectual skills and physical coordination depend on the healthy development of the muscular and nervous systems. The earliest accomplishments are basic skills such as walking, talking, and feeding themselves. As independence grows, children recognize themselves as individuals, interact more actively with their surroundings, and develop close relationships. By the age of 12, they have usually acquired sophisticated language and numeracy skills and wide-ranging physical abilities.
Between the ages of about 10 and 15, children undergo the dramatic changes of puberty, with maturation of the reproductive organs and the development of secondary sexual characteristics such as breasts and body hair. These physical changes occur some time before emotional maturation, and adolescence is therefore a time of adjustment to adulthood. At the age of 18, young people are considered adults in most societies, although they continue to develop psychologically for many years.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.