A neurotic, schizophrenic and normal control group detected a 1,000 cps. 2 sec. tone with an a priori probability of occurrence of 0.5 against a background of continuous white noise during a specified 4 sec. interval. An index of signal detectability, dprime;, and a decision criterion, β, were calculated from the YES-NO responses for 150 control trials, and 150 trials which were preceded by free electric shock at maximum tolerance level. The results show a decrement in signals detected for the neurotic and schizophrenic group as compared to the normal control, whose detection rate improved significantly. The decision criterion remained unaffected.
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