Differences in auditory signal detection between paranoid and nonparanoid schizophrenics were examined on and off phenothiazine medication.
Compared to normals: (1) paranoids detected signals less accurately and used more conservative decision-making criteria; (2) nonparanoids detected signals less accurately under easy signal-to-noise (S/N) conditions but as well as normals under difficult conditions, they were neither more nor less conservative in the criteria they adopted; and (3) paranoid and nonparanoid subjects had a constant number of commission errors under all S/N conditions, while normals showed an increase with each decrease in S/N ratio.
No significant overall effect of phenothiazine medication on the signal-detection performance of schizophrenics was found. A significant interaction between dosage level and diagnosis was found. The signal-detection measure (d') does not appear to be a direct measure of sensory sensitivity in schizophrenics.