Inhibition through negative priming with Stroop stimuli in schizophrenia.

Stroop stimuli were used to measure the negative priming effect in eight positive and 10 negative schizophrenics, 21 depressive and 35 healthy control subjects in order to test hypotheses of insufficient versus persistent cognitive inhibition in schizophrenia. Data show that schizophrenics do not increase their response times to suppressor Stroop items compared to identical but neutral Stroop stimuli because the insufficiency of their inhibitory processes weakens the distractor-suppression effect. However, pre-exposure of the lexical distractor can compensate for insufficient inhibitory mechanisms in positive but not negative schizophrenics, suggesting more severe deterioration in the latter. Depressed subjects showed a slower development of cognitive inhibition. The results suggest important differences in the temporal evolution of inhibitory processes, and are discussed in terms of Hemsley's (1977) and Frith's (1979) theories.