Can patients with obsessive-compulsive disorder discriminate between percepts and mental images? A signal detection analysis.

Signal detection analysis was used to test three hypotheses for repetitive thoughts and behaviors characteristic of obsessive-compulsive disorder (OCD). Patients might have (a) low sensitivity for the difference between having seen something or having imagined seeing it, (b) a high criterion for this discrimination, or (c) difficulty associating context with information in memory. Subjects judged viewed words or imagined words and later indicated which were actually seen. Patients with OCD discriminated seen from imaged words significantly better than normal control subjects, as evidenced by higher d' scores on a recognition memory task. Groups did not differ in response criterion, beta, used to decide whether words had been seen or imaged. Implications for the study of OCD from an information-processing perspective are discussed.