PERIODS OF CHILDHOOD

For our discussion of childhood, we have divided it into the following five periods:

Prenatal period—conception to birth

Infancy and toddlerhood—birth to age 3

Early childhood—ages 3 to 6

Middle childhood—ages 6 to 12

Adolescence—ages 12 to 18

Let us preview these stages.

Prenatal Stage

The prenatal stage is the period of greatest physical growth in the life span, when the human being goes from a single cell (a zygote) to—9 months later—a being made up of billions of cells. The basic body structure and organs are formed, making this a time of great vulnerability, especially during the first 3 months. Brain development in the womb also seems to make possible the begin­nings of learning, as some exciting recent research suggests.

Infancy and Toddlerhood

The first part of the second stage, infancy, lasts for the first IV2 to 2 years of life. While newborn babies (neonates) are of course dependent on adults, they are amazingly competent. Infants can use all their senses right from birth and are capable of simple learning. And these skills improve rapidly. Infants form at­tachments to their parents, their brothers and sisters, and other caregivers, who in turn become attached to them.

During toddlerhood, which lasts from about 18 months to 3 years of age, children become highly skilled in language and motor abilities, and they become quite independent. Although children of this age usually spend most of their time with adults, they show a geat deal of interest in other children.

Early Childhood

During the years from 3 to 6, language becomes more important in children's lives. It lets them communicate better with playmates, as well as with adults. By this age, children are better able to ask for and get what they want, to take care of themselves, and to exercise self-control. Although children already reflect many influences of their culture, they still have much to learn. In their language, play, and drawing, they display an exciting breadth of imagination and inven­tiveness.

During these years, children absorb many aspects of their particular culture, and although adults tend to consider these years the most typical ones of child­hood, specific activities vary greatly from one culture to another. For example, an urban American child may learn how to operate a computer, while a child of the same age in rural France may learn to take produce to town and sell it at market, and while a third child, in east Africa, might learn how to treat injuries suffered by cattle as they are herded across the plains. All three of these children are pursuing a similar underlying purpose—preparing for adulthood.

Adolescence
The most important concern during the ages of about 12 to 18 is the search for identity, a concern that may echo throughout life. The many physical changes that signal the onset of adolescence influence young people's lives in many ways, and the cognitive changes that allow them to engage in abstract thought mean that their intellectual horizons can expand to include a world of possibili­ties. The teenage years see an increased involvement with peers amid efforts to separate from the parental nest. Although culture affects development in every stage, it is particularly influential in adolescence. Some societies see this period as a form of early adulthood, and many traditional societies celebrate puberty rites to mark a young person's "coming of age." In western societies, no one marker signals the end of adolescence.

INFLUENCES ON CHILDREN'S DEVELOPMENT
As we noted when we described Vicky and Jason in the Introduction, children are subjected to countless influences. First, as we will explain in Chapter 2, children are influenced by the genes that they inherit from their parents. That basic influence is then affected by a host of other kinds of influences that come under three categories: normative age-graded influences, normative history-graded in­fluences, and nonnormative life events (Baltes, Reese, & Lipsitt, 1980)  

Normative Age-Graded Influences
When we say that something is normative, we mean that it occurs in a similar way for most individuals in a given group. An age-graded influence is one closely related to chronological age. Normative age-graded influences, then, are influ­ences on development that are highly similar for all people in a given age group. They include such biological events as puberty, as well as such cultural events as entry into formal education (which occurs at about age 6 in most societies today).

Normative History-Graded Influences
Biological and environmental influences that are common to people of a particu­lar generation, or cohort (those growing up at the same time and in the same place), are referred to as normative history-graded influences. These influences include the worldwide economic depression of the 1930s, the political turmoil in the United States during the 1960s and 1970s caused by the war in Vietnam, and the concern about acquired immune deficiency syndrome (AIDS) during the 1980s. These influences also encompass such cultural factors as the changing