Twinning is associated with an increased risk of left-handedness and inverted writing hand posture.
Left-handedness and inverted handwriting postures are more frequent among birth-stressed individuals. Because twinning is also associated with increased birth risk, 298 twins were compared to 1192 age and sex matched singletons. Both left-handedness and inversion were significantly more common in twins, although other indexes of laterality were not affected.
Coren
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Psychology Department, University of British Columbia, Vancouver, Canada.
D000328:Adult; D005260:Female; D007839:Functional Laterality; D006236:Handwriting; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic