Detection of underreporting on the MMPI-2 in a clinical population: effects of information about validity scales

We investigated the effects of information about the MMPI-2's validity scales on underreporting of symptoms in a clinical outpatient population. Adults participating in outpatient psychotherapy were randomly assigned to a standard control group or to one of two groups given instructions and incentives to underreport symptomatology. One of the underreporting groups was given brief information about the presence of validity scales designed to detect respondents attempting to create an unrealistically positive impression. The other underreporting group was given no information about the validity scales. A demographically matched group of adults from the general population who had completed the MMPI-2 under the standard instructions comprised a second control group. Results suggested that traditional and supplementary underreporting scales were reasonably effective in discriminating uncoached underreporters from standard profiles completed by both the clinical and the general population groups. These scales were somewhat less accurate in discriminating coached underreporters from either clinical or nonclinical standard respondents. These findings are consistent with previous results from a college student population suggesting that coaching about validity scales may interfere with the test's ability to detect underreporting respondents, although a few supplementary underreporting scales show promising resistance to the effects of coaching.