Human development is the process of aging. Biological aging involves growth, maturation and degeneration. One way to categorize human development is by age groups. Although individuals differ in factors affecting human development, including activity level, physical and mental health, and environment, categorizing based on age provides an overview of human development.
Neonatal
The neonatal period of human development is the first month of a baby’s life after birth, according to “Psychology: The Developing Person” by Dr. David Myers. Newborns are equipped with reflexes to help with survival, such as the rooting reflex, which is when the baby’s mouth opens for feeding after being touched on the cheek. Also, newborns seem to have an innate preference to look toward faces, according to a study published in the September 1999 issue of Psychological Science.
Infancy
Infancy is the age of 3 weeks to 1 year, according to “Psychology.” During infancy, nerve connections in the brain interconnect rapidly. The developing brain permits physical coordination. More complex motor skills develop, such as sitting, standing and walking, as an infant’s nervous system and muscles grow. Infants experience the world through touching, looking and grasping. Attachment is important in infancy. As described in a classic study by Dr. Harry Harlow published in the 1971 issue of American Scientist, infant monkeys who do not form warm and responsive attachments with caregivers become withdrawn, anxious and violent. Similar behavior has been seen among babies who are abused, neglected or without a nurturing caregiver.
Childhood
Childhood is from 1 year of age to puberty, or the beginnings of sexual maturity, as noted in “Psychology.” For girls, puberty may begin from 9 to 15 years of age, whereas boys may experience puberty at ages 12 to 16 years. During childhood, the nerves in the brain continue to grow and interconnect. Motor skills become more refined. Young children are egocentric and unable to reason logically, according to developmental theorist Dr. Jean Piaget. At about 7 to 11 years of age, children begin to think logically, perform mathematical operations and think concretely.
Adolescence
Adolescence begins with puberty, according to “Psychology.” Reproductive organs, external genitalia and nonreproductive features, such as facial hair in boys and breasts in girls, develop during adolescence. Abstract thinking also develops in the adolescent period, according to Piaget. Adolescence is also marked by the separation from parents. The achievement of adult independence marks the end of adolescence.
Adulthood
Establishing a career, finding a life partner and starting a family traditionally characterize early adulthood. In middle adulthood, declines in strength and stamina become more noticeable and women experience menopause. During older adulthood, physical declines continue and individuals confront the expectation of their own deaths. The ability to process information slows down and the ability to solve new problems decreases in older adulthood. However, verbal skills are not affected with age, according to a study published in the July-September 1989 issue of Intelligence.
References
- "American Scientist"; From Thought to Therapy: Lessons from a Primate Laboratory; Harry Harlow, Ph.D., Margaret Harlow, Ph.D. and Stephen Suomi, Ph.D.; September - October 1971
- The Child’s Conception of Physical Causality; Jean Piaget, Ph.D.; 1930
- "Intelligence"; Age and WAIS-R Intelligence in a National Sample of Adults in the 20-to74-Year Age Range: A Cross-Sectional Analysis with Educational Level Controlled; Alan Kaufman, Ph.D., Cecil Reynolds, Ph.D., and James McLean, Ph.D.; July - September 1989
- Psychology: The Developing Person; David Myers, Ph.D.; 2004
