A test of the interference and normal associate bias theories of schizophrenic cognitive deficit.

The performances of schizophrenics, psychiatric controls, and normals on No Distractor, Irrelevant Distractor, and Associate Distractor memory tasks matched for length, reliability, and difficulty were compared to evaluate the interference theory and a variation of the normal associates bias theory of schizophrenic thought disorder. The distractors had greater negative impacts on the performances of the schizophrenics than on those of the normals or psychiatric controls. However, the associate distractors did not interfere with the learning of the schizophrenics more than the irrelevant distractors did. The results offer strong support for interference theories of schizophrenic thought disorder, but the hypotheses we developed from Chapman and Chapman's (Disordered Thought in Schizophrenia, Appleton-Century-Crofts, New York, 1973) normal associate bias model did not assist in predicting our results.