The relationship between cognitive inhibition and psychotic symptoms.

Cognitive models of schizophrenia have highlighted deficits of inhibitory attentional processes as central to the disorder. This has been investigated using "negative priming" (S. P. Tipper, 1985), with schizophrenia patients showing a reduction of negative priming in a number of studies. This study attempted to replicate these findings, but studied psychotic symptoms rather than the broad diagnostic category of schizophrenia. Psychotic individuals exhibiting positive symptoms were compared with asymptomatic psychiatric patients and with a normal control group. As predicted, the symptomatic group failed to show the usual negative priming effect, which was present in the asymptomatic and normal groups. A modest but significant correlation was found between negative priming and delusions. Neither diagnosis, nor affective or negative symptoms, nor chronicity, nor medication, was related to negative priming. These data replicate previous findings that positive symptoms are related to a reduction in cognitive inhibition, although considerable variability was observed among the psychotic patients.