Conventional and actuarial methods to detect response distortion on the basic personality inventory.

Abstract

Response distortion remains a significant issue in the assessment of psychopathology. Here four groups of psychiatric patients, each of 40 people, were asked to respond honestly or to distort their presentation as either worse, better, or a "normal" pattern of responses to the Basic Personality Inventory (BPI; Jackson, 1989); only those cases showing acceptable consistency in responding ("person reliability") were analysed. Performance of the conventional cutting points on the BPI validity scales were compared with results from linear discriminant analysis calculated for the patients and from those variables selected previously for university students by Helmes and Holden (1986). Preliminary analyses showed that the "good" and "normal" groups could not be separated; the normal group was therefore not included in subsequent analyses. Results showed better classification results for discriminant functions than for the use of the standard BPI validity measures. Contrary to findings using multiple regression, heuristic weights were the least accurate. Implications for applications of the BPI involving suspected response distortion are discussed, along with the unexpected finding of poor performance of heuristic classification functions.Keywords: faking, random responding, Basic Personality Inventory, discriminant analysis, person reliability Methods of detecting distorted response patterns on multiscale measures of psychopathology have a long history, dating to the early development of the F, L, and K scales of the Minnesota Multiphasic Personality Inventory (MMPI; Greene, 2000;Hathaway & McKinley, 1976). Methods based upon these scales in both the MMPI and MMPI-2 have generally worked well when applied appropriately in both simulation studies and in actual practise to detect attempts to over-or underreport levels of pathology (see Bagby, Marshall, Bury, Bacchiochi, and Miller (2006) and Wetter, Baer, Berry, and Smith (1992) for reviews of the MMPI/MMPI-2 and dissimulation).In applied settings where such tests are used, the stakes of taking a measure of psychopathology are often high and there thusly may be significant external incentives to distort responses. Such contexts for presenting a distorted, inaccurate set of responses include the insanity defence for serious criminal charges (prompting overreporting) or seeking a highly desired job (prompting underreporting). More common situations in most clinical practises are likely those of distressed individuals who overemphasize their distress to gain therapist sympathy and those who seek to minimise real distress out of a fear of appearing "crazy" or to preserve a positive image of themselves.There is thusly value in examining the performance of measures of psychopathology that have indices to detect response distortion to determine how well those indices perform with different samples. For measures of psychopathology, samples of people with genuine mental health problems provide a more realistic context for evaluating measures of response distortion than, for exam...