Mother's Hormones Impact a Child's Propensity for Shyness

As we learn more about maternal hormones and their influence on the developing brain, scientists are beginning to propose actual biological mechanisms for the kind of folk prophecies that have been around for ages. One recent study, for instance, suggests that a child's shyness is determined, in part, by maternal hormone fluctuations during gestation. Researchers who interviewed several thousand preschoolers in both the United States and New Zealand noted a significant relationship between the incidence of extreme shyness or inhibition (children who seem particularly fearful, anxious, or withdrawn in the presence of a stranger) and the amount of daylight their mothers were exposed to at midpregnancy. Thus, in the United States, only 12 percent of children born in October-November-December were rated as highly inhibited, compared to nearly i8 percent of those born in April-May-June. In New Zealand, where daylight hours are reversed, children showed the opposite pattern, with more shy children born in October-November-December than in April-May-June. Because the production of certain hormones, like melatonin, is known to fluctuate with the amount of daylight in each season, the researchers propose that such substances may subtly alter brain development during a critical period at midgestation, when massive numbers of neurons are migrating to form the basic architecture of the cerebral cortex. (It is also possible that other seasonal differences, like changes in women's diets, physical activity, or exposure to colds and flu. mediate this relationship.)

There appears to be a correlation between the amount of sunlight to which a mother is exposed mid-pregnancy and how shy her children are later on.