Hypothesis testing in patients with chronic progressive multiple sclerosis.

Patients with chronic progressive MS (N = 38) were compared with an age and education matched medical control group (N = 19) on a visual discrimination task designed to evaluate hypothesis testing and focusing behavior. Thirty-three MS patients (85%) and all control patients were able to formulate and use hypotheses, but MS patients were less likely to employ strategies leading to a correct solution. Furthermore, MS patients were more likely to perseverate with one strategy despite negative verbal feedback. Five MS patients were unable to formulate hypotheses. These findings suggest that MS patients have impaired cognitive functioning in addition to previously reported problems with memory.