title: Association of handedness and birth order in monozygotic twins.
abstract: In a random sample of 104 pairs of middle-class Caucasian, handedness-discordant twins six years of age or older, a significant relationship has been found between birth order and handedness in monozygotic twins, there being an excess of left-handed among first-born twins (P less than 0.01). No such relation has been found in dizygotic twins.
mesh_terms: D001722:Birth Order; D002648:Child; D005260:Female; D007839:Functional Laterality; D006801:Humans; D011247:Pregnancy; D013223:Statistics as Topic; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic