A new look at reaction time in schizophrenia.

Schizophrenia patients demonstrate impaired manual reaction time (RT), but not saccadic RT, when given traditional tasks. To determine whether the manual RT time impairment could be eliminated by providing imperative stimuli to the finger (thus providing stimulus-response compatibility), we tested 28 chronic schizophrenic patients on finger-lift RT to visual (VIS), tactile plus visual (TAC+VIS), and auditory plus tactile plus visual (AUD+TAC+VIS) stimuli. The patients (a) were significantly slower than controls (n=28) in all three tasks, (b) showed bimodality, with 43% of patients having means and variances nearly identical to control values, and (c) had RTs significantly closer to control values in the TAC+VIS and AUD+TAC+VIS tasks than in the VIS task. The inability to normalize finger-lift RT in schizophrenia represents a genuine slowing of this response system regardless of stimulus-response compatibility. We consider other possible explanations for the differences between manual and saccadic RT, including the notion that excess processing capacity for saccadic RT may be masking possible deficits in that system.