BEHAVIOR PROBLEMS IN 5-YEAR-OLD MONOZYGOTIC AND DIZYGOTIC TWINS - GENETIC AND ENVIRONMENTAL-INFLUENCES, PATTERNS OF REGULATION, AND INTERNALIZATION OF CONTROL

Genetic influence on externalizing problems, internalizing problems, a nd attentional/activity problems in 5-year-olds was consistently ident ified across informants and assessment contexts. Effects of the shared environment were identified as well but with less consistency (i.e., only from parents, not teachers, and more from father than mother repo rts). Correlations between observed patterns of regulation at ages 3, 4, and 5 years and behavior problems at age 5 years were often signifi cant, but low in magnitude and specific to teacher reports. Adaptive i nternalization of control at each age (e.g., frustration tolerance, ca pacity to attend and focus, good impulse control) predicted fewer exte rnalizing problems. Internalization of standards, reflected in childre n's moral themes, understanding of reciprocity, and constructive socia l problem solving, also were sometimes associated with fewer problems. Significant correlations were low in magnitude and again specific to teacher reports. Externalizing problems were more prevalent for boys t han girls, and regulation (i.e., internalization of control and standa rds) was more characteristic of girls than boys.