Conceptual disorder in schizophrenia as a function of encoding orientation.

This study evaluated the hypothesis that schizophrenic conceptual disorder derives from abnormal verbal encoding, geared to salient affective and physical cues at the expense of conceptual attributes. Subjects were 63 adult psychotic inpatients, including 42 schizophrenics and 21 nonschizophrenics of similar age, sex, race, and chronicity. They underwent 12 trials on Wickens' release from proactive interference (PI) procedure to measure reliance on three dimensions for encoding: conceptual (taxonomic class), affective (Evaluation axis of the semantic differential), and physical (rhyming sounds). The release effect for schizophrenics, compared with controls, was found to be significantly weaker on the conceptual dimension and correspondingly stronger on the affective dimension. Whereas controls exhibited the normal attraction to conceptual over other cues, schizophrenics presented a flat profile. Nonparanoid and thought-disordered schizophrenics showed particular deficits on the conceptual dimension. All schizophrenic groups contrasted controls by their diminished PI release with less salient concepts. The results thus suggested that encoding by schizophrenics is uniquely oriented to stimulus salience rather than semantic relevance. A fundamental deficiency in processing of cues essential for conceptual operations, accordingly, seems to underlie the conceptual dysfunction in schizophrenia. The implications were discussed in relation to diversities in the cognitive literature and prevalent theories.