Many psychologists have proposed stage theories of development, which
argue that people pass through stages in specific orders, with
challenges related to age and different capacities emerging in each stage.
Sigmund Freud first described personality development in
terms of stages and believed personality developed by age five.
Erik Erikson proposed a theory of psychosocial development
that occurs in eight stages over a person’s lifetime. He proposed that people
face new challenges at each stage: trust vs. mistrust, autonomy vs. shame and doubt, initiative vs.
guilt, industry vs. inferiority, identity vs. role
confusion, intimacy vs. isolation, generativity
vs. self-absorption, and integrity vs. despair.
Jean Piaget’s theory of cognitive development states that
children develop schema or mental models to represent the world. He
proposed four stages of cognitive development: the sensorimotor
period, the preoperational period, the concrete
operational period, and the formal operational period.
Lawrence Kohlberg proposed a theory of moral development that
includes three levels or stages: the preconventional level, the conventional level, and the postconventional
Prenatal development occurs between conception and birth.
Prenatal development is divided into three stages: the germinal
stage, the embryonic stage, and the fetal
Infancy and Childhood
Motor development or increasing coordination of muscles
improves rapidly in infancy and childhood.
Maturation is genetically programmed growth and development.
Maturation and experience influence motor development.
Temperament refers to the personality features a person is
born with. Alexander Thomas and Stella Chess proposed
three basic types of temperament: easy, slow to warm up, and difficult.
Attachment is the close bond between babies and their
caregivers. Margaret and Harry Harlow concluded that attachment
requires contact comfort, which is the comfort deriving from
After conducting an experiment called the Strange Situation, Mary Ainsworth proposed three types of attachment styles: secure attachment, anxious-ambivalent attachment, and avoidant attachment.
Separation anxiety is the emotional distress infants show
when separated from people to whom they are attached.
Gender is the learned distinction between masculinity and
femininity. Gender stereotypes are societal beliefs about the
characteristics of males and females.
Depending on their perspective, researchers ascribe different causes for
Pubescence refers to the two years before puberty and entails
growth spurts and the development of secondary sex characteristics. Secondary sex characteristics are sex-specific physical traits
that are not essential to reproduction, such as breasts, widened hips, facial
hair, and deepened voices.
Puberty, the point at which sexual organs mature, occurs at
the beginning of adolescence. Menarche refers to the first
On average, puberty occurs between ages ten and fifteen for girls and
eleven and sixteen for boys. Maturing before or after these ages can have
The search for identity is an important step in adolescence. James Marcia
described four identity stages: identity foreclosure, identity moratorium, identity diffusion, and identity achievement.
Adulthood usually includes experiences such as marriage, parenthood, the
empty nest, the midlife crisis, menopause, and aging.
Social clocks indicate the typical life events, behaviors,
and concerns for a particular age.
As people age, they tend to experience loss of neurons in the brain, a
decline in vision and hearing, and decreased memory. People may also experience
increased crystallized intelligence, which is intelligence based on
accumulated knowledge and skills. Physical exercise and mental stimulation can
create new neural brain connections, and older adults generally have a better
sense of well-being.