Nature and Nurture (page 2)

By — Pearson Allyn Bacon Prentice Hall
Updated on Jul 20, 2010

Inherited tendencies make children more or less responsive to particular environmental influences. Because of their genetic makeup, some children are easily affected by certain conditions in the environment, whereas others are less affected (Rutter, 1997). For example, children who are, by nature, inhibited may be quite shy around other people if they have few social contacts. If their parents and teachers encourage them to make friends, however, they may become more socially outgoing (Arcus, 1991; J. Kagan, 1998). In contrast, children who have more extroverted temperaments may be sociable regardless of the environment in which they grow up: They will persistently search for peers with whom they can talk, laugh, and spend time.

Environment may play a greater role in development when environmental conditions are extreme rather than moderate. When youngsters have experiences typical for their culture and age-group, heredity often plays a strong role in their individual characteristics. Thus, when children grow up with adequate nutrition, a warm and stable home environment, and appropriate educational experiences, heredity affects how quickly and thoroughly they acquire new skills. But when they have experiences that are quite unusual—for instance, when they experience extreme deprivation—the influence of environment outweighs that of heredity (D. C. Rowe, Almeida, & Jacobson, 1999). For example, when children grow up deprived of adequate nutrition and stimulation, they may fail to develop advanced intellectual skills, even though they had the potential for such development when they were born (Plomin & Petrill, 1997; D. C. Rowe, Jacobson, & Van den Oord, 1999). Similarly, when malnourished, children tend to remain short in stature regardless of their genetic potential to be tall (J. S. Kagan, 1969).

Timing of environmental exposure matters. When children are changing rapidly in any area, they are especially prone to influence by the environment. For example, early in a mother’s pregnancy, her use of certain drugs may damage the quickly growing organs and limbs of the developing fetus. Just prior to birth, exposure to the same drugs may adversely affect the baby’s brain, which at that point is forming the connections that will permit survival and the ability to learn in the outside world.

In a few cases environmental stimulation must occur during a particular period for an emerging ability to become functional (Blakemore, 1976; Hubel & Wiesel, 1965). In such cases there is a critical period for stimulation. For example, at birth, certain areas of the brain are tentatively reserved for processing visual patterns—lines, shapes, contours, depth, and so forth. In virtually all cases, infants do encounter adequate stimulation to preserve these brain circuits. However, when cataracts are present at birth and not removed for a few years, a child’s vision is obstructed, and areas of the brain that otherwise would be devoted to vision lose some of this capacity (Bruer, 1999).

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