Prior time uncertainty reduction of foreperiod duration in schizophrenia and old age

Four groups of college students, alcoholics, schizophrenics, and old age Ss judged stimulus durations of .50 and .55 seconds. The stimulus was preceded by a sound that functioned as the warning signal. The foreperiod duration, that is, the interval between the onsets of the warning signal and the stimulus, was variable and was either 1,3, or 5 seconds. There was no group difference with respect to the effect of foreperiod variability. Estimation of stimulus duration was a monotonically increasing function of foreperiod duration. However, when pitch of the sound was correlated with the corresponding foreperiod duration, this monotonic relation between foreperiod duration and estimation of stimulus duration was eliminated for schizophrenics, but not for nonschizophrenics. Although schizophrenics were not distinguishable from nonschizophrenics in terms of the effect of foreperiod variability, receptivity to prior information associated with time uncertainty reduction was shown to be unique for schizophrenia.