A cross-sectional behavioral genetic analysis of task persistence in the transition to middle childhood.

Task persistence, measured by a composite score of independent teacher, tester and observer reports, was examined using behavioral genetic analysis. Participants included 92 monozygotic and 137 same-sex dizygotic twin pairs in Kindergarten or 1st grade (4.3 to 7.9 years old). Task persistence was widely distributed, higher among older children, positively associated with standardized tests of cognitive performance and achievement, and negatively associated with parents', teachers' and observers' reports of behavioral problems. Cross-sectional analysis indicated a strong developmental shift from shared environment variance among younger children to additive genetic variance in older children.