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Abstract: Children''s negative characteristics are thought to be a factor in evoking hostile parenting responses. This can result in genotype/environment correlations (rGE) in which children''s heritable traits influence the parenting they experience. We did genetic analyses on 292 mothers’ self-reported hostile-reactive behaviors toward each of their twins at 5, 18 and 30 months. Finding heritability for a parenting behavior analyzed as a child phenotype is evidence of rGE correlation. The heritability of maternal behavior was modest (29% at 5 months, 0% at 18 months, and 25% at 30 months) and longitudinal analyses indicated that genetic factors at 5 and 30 months were uncorrelated. Common environment factors, probably reflecting characteristics of the mothers, were the main source of variance at the three ages and were highly correlated through time. We concluded that children''s heritable characteristics evoked maternal negative response at specific times, but were not responsible for the stability of maternal hostility from infancy to toddlerhood. [Copyright &y& Elsevier]

Little is known about why people differ in their levels of academic motivation. This study explored the etiology of individual differences in enjoyment and self-perceived ability for several school subjects in nearly 13,000 twins aged 9–16 from 6 countries. The results showed a striking consistency across ages, school subjects, and cultures. Contrary to common belief, enjoyment of learning and children’s perceptions of their competence were no less heritable than cognitive ability. Genetic factors explained approximately 40% of the variance and all of the observed twins’ similarity in academic motivation. Shared environmental factors, such as home or classroom, did not contribute to the twin’s similarity in academic motivation. Environmental influences stemmed entirely from individual specific experiences. [ABSTRACT FROM AUTHOR]