Using Diagnostic Efficiency Statistics to Evaluate the Concurrent Validity of the Perceptual Aberration Scale

Abstract

We evaluated the diagnostic efficiency of the 35-item Perceptual Aberration Scale (PAS; Chapman, Chapman, & Raulin, 1978) in selecting schizotypal college students using the presence of a Minnesota Multiphasic Personality Inventory, (MMPI: Hathaway & McKinley, 1940) code type associated with the schizophrenia spectrum as indicative of schizotypal status. The PAS was able to reliably rule out the presence of schizotypy among women and men producing very low (less than or equal to 3) PAS scores. Among women, only extremely high PAS (greater than or equal to 28) reliably predicted schizotypal MMPI status. Among men, however, no PAS cutting score was reliably associated with the presence of a schizophrenia-related MMPI code type, suggesting that the PAS should not be used to define schizotypy among male college students. The PAS cutoff values that maximized accurate identification of women with schizotypal features and identification of women and men without schizotypal features are considerably more conservative than those that have been traditionally used in research using the PAS as a screening device. The data presented here suggest that using traditional PAS cutoffs (scores greater than or equal to 2 SD above the mean and less than or equal to .5 SD below the mean) may result in unacceptably high diagnostic error.