Lateral preferences in children with intellectual deficiency of idiopathic origin.

The goal of this study was to evaluate lateral preferences in a population of children with intellectual deficiency of idiopathic origin, compared with those of typically developing (TD) children. Two groups of children with mild or moderate intellectual deficiency were observed. Handedness (using a 10-item test and Bishop's card-reaching task), eyedness and footedness were studied. The younger group consisted of sixteen 10- to 11-year olds; the older group comprised fourteen 12- to 14-year olds. A control group of fifteen TD children was matched for age with the younger group of intellectually deficient (ID) children. The results show that the occurrence of left-handedness is not higher in children with ID of unknown origin than in age-matched TD children. However, we observed a marginally reduced tendency toward right-handedness in ID than in TD children: more mixed-handers among ID than TD children; test-retest consistency of hand preference significantly lower in the 10- to 11-year-old ID children than in the age-matched TD children; greater tendency of ID children to use their nonpreferred left hand when the card was presented to the left, as compared with TD children. Left-eyedness and crossed hand-eye preference were also more frequent in ID than in age-matched TD children. No age-related difference in laterality was found in ID children. These results partially support other studies indicating that less rightward asymmetry is associated with intellectual deficiency in children.