>Background: Semantic memory deficits in schizophrenia have been investigated for decades. These seem particularly sensitive and exacerbated in those with thought disorder (TD). Semantic priming has been common among the tasks used to index these deficits. However, difficulty has been encountered in the definition and measurement of TD, where typical assessments have relied on measures with a limited number of endorsed items that exhibit positive skew. >Methods: A long-SOA semantic priming task (lexical decision) was administered to 26 individuals with either schizophrenia or schizoaffective disorder, as well as to 26 healthy controls. Participants also completed a 29-item self-report questionnaire in terms of the frequency with which they had experienced various symptoms of TD. >Results: Although evidence of semantic priming was found using a 2 (semantic relatedness) × 2 (diagnostic group) mixed-design ANOVA, this priming did not differ significantly between those with schizophrenia and controls (ie, there was no interaction between semantic relatedness and diagnostic group on lexical decision reaction times). Nevertheless, there was a trend-level (P = .096) group effect on semantic priming when individuals with schizophrenia were sub-grouped into those who had higher and lower levels of self-reported TD. Moreover, there was a weak positive association between total self-reported TD and the priming effect (r = .25, P = .046). >Conclusion: These results are consistent with abnormal semantic function and hyper-priming in those with TD and demonstrate the continuum of its severity across diagnostic groups. Further work is being conducted to investigate the functional neuroimaging underpinnings of these semantic deficits.
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