A study of parent ratings of internalizing and externalizing problem behavior in 12-year-old twins.

OBJECTIVE Studies on 3-, 7-, and 10-year-old twins' internalizing and externalizing problems have emphasized the importance of understanding sources of agreement and disagreement between maternal and paternal ratings. A psychometric model that assumes that each parent assesses rater-specific aspects of the child's behavior provided the best explanation for parental disagreement. This study investigates two models that have been used to explain the agreement and disagreement between mothers and fathers in the ratings of their children. METHOD Child Behavior Checklists filled in by mothers and fathers were collected for a sample of 1,481 twelve-year-old twin pairs. Genetic and environmental influences on internalizing and externalizing problems were estimated using models that corrected for rater bias, rater-specific effects, and unreliability. RESULTS The psychometric model fitted the data significantly better than a rater bias model. Significant influences of genetic, shared, and nonshared environmental factors were found for internalizing and externalizing behavior. Parent-specific views, rater bias, and unreliability were significant. CONCLUSIONS The best-fitting model implies that disagreement between parents is due to the fact that mothers and fathers provide information from their own perspective. This information should be seen as important and adding to the diagnostic formulation rather than as a point of disagreement. The finding that internalizing and externalizing problems are influenced by genetic and environmental factors fosters the understanding that it is the interaction of nature and nurture that puts children at risk for common behavioral disorders.