Parenting as a reaction evoked by children's genotype: a meta-analysis of children-as-twins studies.

Parenting has been extensively studied but mostly as a causal factor influencing child outcomes. The aim of the current article is to examine the child's side of the relationship by meta-analyzing studies which used quantitative genetic methods that provide leverage in understanding causality. A meta-analysis of 32 children-as-twins studies of parenting revealed a heritability estimate of 23%, thus indicating that genetically influenced behaviors of the child affect and shape parental behavior. The shared- and nonshared-environmental estimates, which amounted to 43% and 34%, respectively, indicate not only substantial consistency in parental behavior but also differential treatment within the family. Assessment method, age, and parenting dimension were found to be significant moderators of these influences. Our findings stress the importance of accounting for genotype-environment correlations in child-development studies and call into question previous research that interpreted correlational results in unidirectional terms with parenting as the sole causal factor.