title: Environmental and genetical causes of variation in ethological aspects of behavior in two-year-old boys.
mesh_terms: D000704:Analysis of Variance; D001519:Behavior; D002675:Child, Preschool; D005010:Ethology; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008954:Models, Biological; D010287:Parent-Child Relations; D011247:Pregnancy; D012931:Social Environment; D014427:Twins