Abstract

Our behavior is predicated on mental models of the environment that must be updated to accommodate incoming information. We had 13 right-brain--damaged (RBD) patients and 10 left-brain--damaged (LBD) patients play the children’s game ‘‘rock, paper, scissors’ ’ against a computer opponent that covertly altered its strategy. Healthy age-matched controls and LBD patients quickly detected extreme departures from uniform play (‘‘paper’ ’ chosen on 80 % of trials), but the RBD patient group did not. Seven RBD patients presented with neglect and although this was associated with greater impairment in strategy updating, there were exceptions: 2 of 7 neglect patients performed above the median of the patient group and 1 of the 6 nonneglect participants was severely impaired. Although speculative, lesion analyses contrasting high and low performing patients showed that severe impairments were associ-ated with insula and putamen lesions. Interestingly, relative to the controls, the LBD group tended to ‘‘maximize’ ’ choices in the strongly biased condition (i.e., optimal strategy chosen on 100 % of the trials), whereas controls ‘‘matched’ ’ the computer’s strategy (i.e., optimal strategy chosen on 80 % of the trials). We conclude that RBD leads to impaired updating of mental models to exploit environmental changes.