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.
Pre-natal development includes some primitive reflexes. Some scientists believe that these reflexes are vestigial and have limited use in life, whole others suggest that these are the building blocks for the development of infant's senses and movements. Primitive reflexes reappear in adults under certain conditions, such as neurological conditions like dementia or traumatic lesions. The infancy stage is from birth to the onset of speech. Babies spend most of this time sleeping. Scientists say that infants have six states, grouped in pairs: quiet sleep and active sleep, quiet waking and active waking, fussing and crying.
In the babyhood stage children show signs of intelligence through the use of symbols. The language they use matures and babies develop memory and imagination. Thinking is not logical with prevalence of egocentric thinking. Early childhood is also known as pre-school age, exploratory age and toy age. In this period children expand their social horizons and pay more attention to people around them.
Late childhood is the period when children show logical and operational thinking. Children learn to make things and use tools, and acquire different skills. Adolescence is the period of life between the start of puberty and the full commitment to an adult social role. In this period people develop personal and social identity. Adolescence has two stages: early adolescence (from 13 to 16 years) and late adolescence (from 16 to 19 years).
In the early adulthood people usually learn how to have intimate relationships. Middle age is the period from 40 to 60 years. Old age is the stage between 60 and 80 years. People experience a conflict between integrity and despair. When reflecting on their life, they either feel a sense of accomplishment or failure.
Although chronological age is often associated with stage of development, scientists have not proved that this is always the case. Culture can affect development as much as biology. Age determines structured social roles and statuses, but environmental influences such as child-rearing practices and cultural concerns may result in different patterns of expectations and development.
Life-span developmental psychologists also say that throughout the whole life cycle people have several common basic needs: love, social contact and attachment, outlets for aggression and opportunities to develop mastery and competence.