Visual detection threshold differences between psychiatric patients and normal controls

Previous investigations of the visual sensitivity of psychiatric patients have generally failed to control for confounding due to nonsensory factors. In the present research, visual detection thresholds of acute hospitalized psychiatric patients and nonpatients were obtained using an adaptive, criterion-free, three-interval, temporal, forced-choice double-staircase procedure. In Experiment 1, 23 schizophrenic patients and 13 nonpatient controls were tested; in Experiment 2, 17 schizophrenic patients, 15 patients with major depressive disorder, 15 siblings of schizophrenic probands, and 18 nonpatient controls were tested. Results of both experiments indicated that, on the average, patients required about twice as much luminous energy for absolute threshold detection, with about 50% overlap between patient and control distributions (p <.01 in both studies). The present research suggests that there are differences in visual sensitivity between psychiatric patients and normal controls that cannot be attributed to response-bias factors. Implications of the present findings and directions for future research are discussed.