Twins: behavioral differences.
D001519:Behavior; D001722:Birth Order; D001724:Birth Weight; D002648:Child; D002653:Child Behavior Disorders; D002675:Child, Preschool; D001068:Feeding and Eating Disorders; D005260:Female; D005826:Genetics, Medical; D006801:Humans; D007223:Infant; D007406:Interview, Psychological; D007845:Laughter; D008297:Male; D008423:Maternal Age; D010551:Personality; D011247:Pregnancy; D012893:Sleep Wake Disorders; D012959:Socioeconomic Factors; D014427:Twins