Schizophrenia: a failure to control the contents of consciousness?

Frith (1979) proposed that the 'positive' symptoms of schizophrenia, i.e. hallucinations, delusions, and though disorder, could be accounted for in terms of a defect in the mechanism(s) that controls and limits the contents of consciousness. The present study was designed to test one of the predictions derived from this model; that schizophrenics should fail to inhibit alternative meanings of ambiguous words. As a means of testing this prediction the effects of semantic priming on the 'availability' of subsequent target words to consciousness were assessed, measuring recognition thresholds. The priming conditions employed were expected to either facilitate or inhibit perception of target words in the control groups, normals and depressed patients without psychotic features. A strong priming effect was obtained in the control groups, but was much weaker in the schizophrenic group; this provides some support for the model.