Development
 Conception through Childhood

Developmental psychology is the study of physical and cognitive changes from conception until death. Because the subfield covers a wide range of ages, it uses a number of different methods including the longitudinal, cross sectional, and cohort research designs to answer the questions posed. Developmental psychology also focuses on the nature versus nurture issue in many of the topics it addresses.

We begin life as a zygote, which is the union of a sperm and an ovum. The zygote carries all the genetic material needed for development. There are 23 pairs of chromosomes in each cell; the 23rd pair determines whether we are to be a male or a female. A number of barriers to prenatal development can occur because the embryo and fetus are sensitive to drugs, smoking, and alcohol. The status of the fetus can be checked by using methods such as ultrasound and amniocentesis.

The infant enters the world equipped with a number of reflexes such as the grasp and rooting reflexes. Infants are able to recognize their mother's voice; facial expressions suggest that taste and smell are developed early. Infants can learn via classical conditioning, operant conditioning, and imitation.

The nervous system develops very rapidly at a young age; one major development is myelin sheaths-- this fatty protein substance that covers some axons makes it possible for infants to engage in more physical activity such as walking well at 15 months.

Starting from birth, infants exhibit different temperaments; they may be easy, slow to warm up, or difficult. Parents quickly learn to predict their infant's typical reactions based on temperament.

Two well known theorists--Sigmund Freud and Erik Erikson proposed stage theories. Freud's theory focuses on psychosexual development; Erikson's theory focuses on dealing with psychosocial crises such as developing trust versus mistrust. Both theorists believed that what happens early in life can have a major impact on later development

Attachment is a reciprocal relationship formed by two people--the most common example is the attachment between an infant and parent. The importance of attachment was highlighted by the Harlows' research with baby monkeys. Subsequent research showed that babies tend to develop different types of attachment; some are securely attached, other are ambivalent. The focus on attachment raised concerns about potential detrimental effects of day care. However, research has shown that babies who attend day care can be just as attached to their parents as babies raised at home. Day care may have social and cognitive benefits, provided the facility is well staffed.

Three different styles of parenting have been identified by psychologists: authoritarian, authoritative, and permissive. Each of them seems to be associated with different outcomes.

Jean Piaget is one of the most influential cognitive theorists; he observed that children proceed through a series of stages of cognitive development beginning with the sensorimotor stage. Piaget also noted the importance of object permanence--the belief that an object still exists even when it is not in view as a milestone in cognitive development. The stages continue with the preoperational stage and concrete operational stage. Theorists have also proposed a stage theory of moral development.  

Adolescents through Old Age

Development continues through adolescence and into old age. The changes that occur can be classified as physical, intellectual, personality/social, and ending with death.

The profound physical changes during adolescence include pubescence--the period of rapid growth and maturation of the sexual organs and the appearance of secondary sex characteristics that precedes puberty. Although the physical changes in early adulthood are less dramatic, middle adulthood ushers in a period characterized by several changes such as those affecting eyesight and hearing; this is also the stage of life when menopause occurs. These physical changes usually accelerate during late adulthood and may include the memory problems indicative of Alzheimer's disease.

The intellectual changes include attainment of Piaget's formal operational stage, assuming an adolescent has had the appropriate educational opportunities. Much of the research on the development of intelligence has focused on two types of intelligence. Fluid intelligence is the ability to see new relationships, solve new problems, form new concepts, and use new information. This type of intelligence may begin a gradual decline at about age 30. However, crystallized intelligence-- the ability to retrieve and use information that has been learned and stored-- may actually increase throughout adulthood.

The key personality and social changes involve dealing with Erikson's stages starting with identity versus role confusion during adolescence. Later, individuals deal with the crisis Erikson called intimacy versus isolation in early adulthood and integrity versus despair in late adulthood. Our attitudes toward death change across the life span, especially as our cognitive abilities develop. When we confront our own death we often proceed through five stages first described by Elisabeth Kubler-Ross. The first stage, denial, is characterized by a "not me" attitude, which becomes "why me?" in the anger stage. The final stage, acceptance, occurs after unfinished business such as finances have been taken care of and the individual accepts the fact that "the time is near."

Culture plays a major role in the behavior of people around the world. For example, prescribed birthing practices vary dramatically across cultures. When people arrive in the United States they carry these practices with them; thus, it is important to understand cross-cultural differences in birthing, parenting, educational achievement, and aging.