Life-span developmental psychology studies the transformations in human behavior from conception throughout life. It examines changes across a broad range of topics including psycho-physiological processes, cognitive development, language acquisition, social, personal and emotional development. It also studies the formation of identity. The main goal of this science is to analyze the general principles of life-long development.
Life-span developmental psychology is studying three components of individual development: interindividual commonalities (regularities), interindividual differences and intraindividual plasticity (malleability). Scientists use two approaches to create life-span theories: person-centered (holistic) and function-centered. The holistic approach treats the person as a system and examines the life-span development by describing and connecting age periods or states of development into one overall pattern of lifetime individual development.
The function-centered approach focuses on a category of behavior, such as perception, information processing, action control, attachment, identity, personality traits, and describes the life-span development according to any of these categories. Awareness of the life cycle, the ages of man can be noticed in the ancient writings of the Talmud, the Chinese sage Confucius and the Greek lawyer and poet Solon. They have some differences due to their religious and cultural context, but identify similar major phases: a formative pre-adult period lasting until ages 15 to 20; an early adult phase lasting from 20 to 40, when a person gets married, creates a family and selects an occupation; middle adulthood, from 40 to 60, when people fully realize their intellectual and moral powers; and late adulthood, beginning at 60.
Solon says that old age is the time of decline, while the Talmud and Confucius both see old age as a time of new growth and freedom as the person becomes a wise elder with new relationships to his origin, his ending and the self. According to modern psychology, life-span development can be divided into several stages: pre-natal, infancy, babyhood, early childhood, late childhood, adolescence, early adulthood, middle age and old age.