The effects of hemispheric dominance, literacy acquisition, and handedness on the development of visuospatial attention: A study in preschoolers and second graders.

A tendency to over-attend the left side of the space (i.e., pseudoneglect) has been repeatedly reported in Western adult populations and is supposed to reflect a right hemisphere dominance in the control of visuospatial attention. This neurobiological hypothesis has been partially challenged by growing evidence showing that pseudoneglect is profoundly triggered by cultural practices such as reading and writing habits. Accordingly, more recent theoretical accounts suggest a strict coupling between nature and nurture dimensions at the origins of such bias. To further explore this possibility, here we first administered a digitized cancellation task to right-handed Western children before and after literacy acquisition. Results showed an incremental leftward shift of attention in the cancellation of the first target and an increasing preference for a left-to-right visual search from preschoolers to second graders. Yet, despite these differences, the overall distribution of visuospatial attention was biased to the left in both groups. To explore the role of handedness in visuospatial asymmetries, we also tested a group of left-handed second graders. Results showed an impact of handedness on visuospatial performance, with an accentuated rightward-oriented visual search for left-handed children, although the overall distribution of attention was again biased to the left hemispace. Taken together, these findings do not provide support to a pure neurobiological view of visuospatial biases. Rather, our study indicates that the control of visuospatial attention is mediated by a dynamic interplay among biological (i.e., right hemisphere dominance), biomechanical (i.e., hand dominance), and cultural (i.e., reading habits) factors.