Nonshared environment and monozygotic adolescent twin differences in effortful control

Effortful control is the regulative dimension of temperament, and plays an important role in the etiology of internalizing and externalizing problems in adolescents. Temperamental traits are thought to be constitutional, but could also be modified by experience. If maternal parenting is an environmental experience for adolescents’ regulative temperamental trait,it should account for effortful control differences between siblings growing up in the same family even after the genetic effect on adolescents’ effortful control is taken into account. This hypothesis was tested in 585 pairs of Chinese monozygotic (MZ) twins. Results revealed that within MZ pairs, the twin receiving more warm, nurturant-involved maternal parenting and less hostile, harsh-inconsistent maternal parenting had a higher level of effortful control. These results suggest that markedly different maternal parenting situations, such as a nonshared environment, have an effect on adolescents’ effortful control. Although effortful control is constitutional, it may be modifiable by experience of parenting.