Disciplines and theories concerned with the cognitive, psychological physiological, and social/interpersonal aspects of human development.

Child psychologists study human development from the earliest stages of life through adolescence and adulthood. These scientists focus on many areas of growth. In the early years of life they include motor skills, perceptual analysis and inference, language and speech, social behavior, and the emergence of basic emotions of fear, sadness, anxiety, shame, and guilt.

The two important strategies for studying development include the longitudinal study in which a particular group of children is studied over a long period of time, sometimes from infancy through adulthood. The second method, which is more popular because it is less expensive, is called the cross-sectional method. In this strategy a group of children or adolescents at a particular age are studied at that age. In order to compare different ages, different samples would...