Representing target motion: the role of the right hemisphere in the forward displacement bias

Patients with left spatial neglect, patients with right hemisphere damage but no neglect, and a control group were asked to judge the final position of a series of moving targets. Both patient groups showed attentional deficits. All 3 groups demonstrated a forward displacement bias, overestimating the final target position along the object trajectory. However, in both patient groups the size of this forward displacement bias decreased as the distance the target traveled before vanishing increased. For horizontally moving targets, at the maximum distance only the control group showed significant forward displacement. For all 3 groups, the direction in which the target traveled had no influence, but the size of the forward displacement increased as target speed increased. Several attentional explanations of these results are considered, including the differential allocation of spatial attention between central and peripheral locations, differences between exogenous and endogenous attention, and deficits in sustained attention.