Patients with Korsakoff's syndrome were compared to brain-damaged and neurologically intact control subjects on visual discrimination tasks designed to evaluate hypothesis testing and focusing behavior. Results show that Korsakoffs can formulate and use hypotheses, but that their strategies are not leading to correct solution. Rather, they perseverate with one strategy even after indications of its inappropriateness. Furthermore, that this pattern of results occurs in the presence of memory aids, suggests that Korsakoffs may have impaired cognitive functioning independent of their retention deficits.