This behavioral genetic study examined perceived competence and self-worth in same-sex twins, siblings, and stepsiblings 10 to 18 years old, and again 3 years later. Findings at second assessment showed six of seven subscales heritable. Genetic contributions to stability were found for perceived scholastic competence, athletic competence, physical…

Examined whether differentiating processes existed for 7 composite indices of positive and negative adolescent adjustment in 720 sibling pairs. Found that siblings born 1 year apart at Time 1 were more similar to each other than were siblings born 2 years apart, suggesting that shared environmental influences counteract sibling differentiation…