A caution on the use of the MMPI K-correction in research on psychosomatic medicine.
The MMPI K scale is widely used to screen for invalid responses and to adjust substantive scale scores for defensiveness. In a normal volunteer sample, correlations of MMPI clinical scales and the Cook-Medley Hostility (HO) scale with self-reports and peer ratings on the NEO Personality Inventory (NEO-PI) were decreased rather than increased by K-correction. Similarly, in a medical sample, structured interview-based ratings of Potential for Hostility were better predicted by uncorrected HO scores than by K-corrected HO scores. Finally, in a prospective study of mortality among lawyers, uncorrected HO scores were a significant predictor of all-cause mortality; K-corrected scores were not. The data suggest that, under some circumstances, the K scale may measure substantive traits rather than defensiveness, and should be used and interpreted with caution. Its use is probably contraindicated for most research on psychiatrically normal subjects.
McCrae
R R
RR
Gerontology Research Center, National Institute on Aging, Baltimore, MD 21224.
Costa
P T
PT
Dahlstrom
W G
WG
Barefoot
J C
JC
Siegler
I C
IC
Williams
R B
RB
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003674:Defense Mechanisms; D005260:Female; D006791:Hostility; D006801:Humans; D008137:Longitudinal Studies; D008950:MMPI; D008297:Male; D008875:Middle Aged; D009497:Neurotic Disorders / Q000523:psychology; D011594:Psychometrics; D011602:Psychophysiologic Disorders / Q000523:psychology*; D012649:Self Concept; D014434:Type A Personality