Prior event uncertainty reduction under two different levels of time uncertainty of foreperiod duration in schizophrenia.

Schizophrenic and alcoholic Ss judged stimulus durations of .50 and .55 seconds. Stimulus was 1, 3 or 5 dark dots and was preceded by variable foreperiod duration of 1, 3 or 5 seconds. Judgment of stimulus duration was found to be a monotonically increasing function of both foreperiod duration and numerosity of dots. When pitch of sound, which functioned as a warning signal, was correlated with numerosity of dots, the monotonic relation between numerosity of dots and estimation of stimulus duration was eliminated for alcoholics, but not for schizophrenics, only when foreperiod duration was constant from trial to trial. The effect of prior information as to numerosity of dots was negligible for both schizophrenics and alcoholics when foreperiod duration was variable from trial to trial.