Valk, J.C. van der

problem behavior influence factor scale problem behaviors model children variance study externalizing internalizing parent rater sample mother child effect rating difference nonshared sibling father assessment correlation estimate externalizing scale group externalizing problems rater bias result zygosity internalizing scale questionnaire chapter internalizing problems sex differences dizygotic interaction family score table psychometric model monozygotic sibling interactions adoptee environment dizygotic twins stability change rater bias model psychiatry monozygotic twins achenbach analysis dutch child behavior checklist ages 3 van der valk psychology adolescent etiology psychometric verhulst point analyses father ratings boomsma development discriminant contribution van den oord population neale information covariance rater differences research experience report