AbstractCompared effects of foreperiod (FP) duration on time estimation (TE) and reaction time (RT). There was no difference between schizophrenics (N= 20) and nonschizophrenics (N= 20) with respect to the effect of FP duration or with respect to the effect of change in FP duration. Prior information about FP duration nullified these two effects on schizophrenics' TE and had a detrimental effect on their RT. Alcoholics' TE and RT were affected little by such prior information. Suppression of preparation by expectancy was shown to be a possible characteristic of schizophrenia.