Research reportHandedness as a marker of cerebral lateralization in children with and without autism

•We report on a detailed set of hand actions from two populations of right-handed boys.•Typically developing boys demonstrated a right hand bias for actions to objects.•Typically developing boys also demonstrated a left hand bias for actions to the self.•Boys with autism revealed mixed-handedness for actions to objects and to the self.•Handedness reveals a dissociation for functional specialization of the hemispheres.

We employed a multiple case studies approach to investigate lateralization of hand actions in typically and atypically developing children between 4 and 5 years of age. We report on a detailed set of over 1200 hand actions made by four typically developing boys and four boys with autism. Participants were assessed for unimanual hand actions to both objects and the self (self-directed behaviors). Individual and group analyses suggest that typically developing children have a right hand dominance for hand actions to objects and a left hand dominance for hand actions for self-directed behaviors, revealing a possible dissociation for functional specialization of the left and right hemispheres respectively. Children with autism demonstrated mixed-handedness for both target conditions, consistent with the hypothesis that there is reduced cerebral specialization in these children. The findings are consistent with the view that observed lateralized motor action can serve as an indirect behavioral marker for evidence of cerebral lateralization.