Right-left orientation and significance of systematic reversal in children.

Shortly before the acquisition of right and left, which generally occurs around age 6-7 years, a very simple right/left discrimination task makes it possible to distinguish groups of children with strikingly different cognitive abilities. Preschool children aged from 5 to 6.4 years were asked to show their left hand, right eye, left ear and right hand. On a variety of simple cognitive tasks exploring verbal fluency, syntactic comprehension, working memory, visuo-spatial ability and number processing, children who made from 1 to 3 errors (14% of the sample) performed significantly worse than those who showed systematic reversal (30%) and those who made no error. Differential use of logical thinking can partially explain these differences. Neuropsychological implications of these developmental findings are discussed.