Semantic context-processing deficit in thought-disordered schizophrenic patients: Evidence from new semantic priming paradigms

Abstract

Introduction. Disorders in the processing of the semantic context are now a well-established phenomenon in thought-disordered (TD) schizophrenic patients, and have been revealed especially well by studies that have made use of the experimental paradigm of lexical decision tasks coupled with semantic priming. The main question addressed by this study was the evaluation of the experimental conditions under which TD schizophrenic patients are able to deploy cognitive strategies for semantic context processing. Methods. We studied semantic priming in two double lexical decision tasks (i.e., involving the explicit processing of the prime word) using a sequential presentation of words (stimulus onset asynchrony; SOA 500?ms) with a different proportion of related words (Experiment 1 with 25% vs. Experiment 2 with 15%) in 15 TD schizophrenic and 15 normal participants. Results. The results showed no significant differences between the semantic priming of TD schizophrenic and normal participants for Experiment 1, unlike Experiment 2 in which we observed a significant reduction of the amplitude of semantic priming in TD schizophrenic patients. The results of Experiment 1 contrast with those obtained previously (Besche et al., 1997) using a classical lexical decision task (implicit processing of the prime word) which also contained 25% related words. Conclusions. Experimental variables, such as the cognitive processing required by the prime word or the proportion of related words or the way they are manipulated, all seem to influence the emergence of semantic priming abnormalities in TD schizophrenic patients.