Minnesota Multiphasic Personality Inventory-2 (MMPI-2) Validity Scales

A strength of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) is its multiple indicators regarding an examinee’s approach to the test. Ideally, examinees answer all questions, respond consistently, and do not distort test findings by overreporting or underreporting experienced psychopathology. However, some individuals may approach the test in a manner that deviates from this optimal scenario, and MMPI-2 profiles can be interpreted with confidence only when these issues have been addressed. Overall, the MMPI-2’s measures of test-taking approach and validity may qualify clinical findings or lend credence to interpretations yielded by the test in multiple situations, particularly in forensic situations such as criminal proceedings as well as in gatekeeping evaluations (e.g., child custody assessments), in which examinees may have motivation to modify their clinical presentation. The most commonly used validity measures include the L (Lie), K (Correction), and F (Infrequency) scales.

A first step in assessing response validity involves evaluating the Cannot Say scale, which indicates the number of unanswered items or items answered both true and false. A high number of such items renders a profile invalid and may suggest that the examinee perceived the items as irrelevant, was uncooperative, was defensive or indecisive, or could not understand the items. Second, to assess response consistency, the Variable Response Inconsistency (VRIN) and True Response Inconsistency (TRIN) scales are evaluated. VRIN measures the degree to which the examinee responded consistently to items similar in content, with logically inconsistent responses of particular note. Though some inconsistent responding is not unusual, high levels suggest that the examinee may have responded randomly or had reading comprehension difficulties or had been confused, careless, uncooperative, or overtly psychotic. TRIN offers additional information about response sets or styles that may affect the profile, measuring the degree to which the examinee responded inconsistently by endorsing items similar in content, but phrased as opposites, as both true or as both false. High scores indicate a tendency to yea-say (i.e., endorse many items as true), and low scores indicate a tendency to nay-say (i.e., endorse many items as false).

Third, the extent to which the examinee accurately self-described symptoms and did not over- or underreport psychopathology is evaluated. Underreporting is more common in personnel, presurgical, or child custody evaluations, whereas overreporting is more common in personal injury or criminal evaluations. Several scales provide information about possible overreporting or symptom exaggeration. The F (Infrequency) scale includes items selected to detect unusual or atypical responses. Reflecting bizarre sensations, strange thoughts, and peculiar experiences, they were answered in the deviant direction by no more than 10% of an early subsample of the normative sample. There are several possible interpretations for elevations on this scale including malingering, random responding, or expressing a “cry for help.” Though different in content relative to F, the Fb (Infrequency-Back) scale is similar in purpose and format, consisting of items at the end of the test, so that response style can be evaluated throughout the entire administration. The F(p) (Infrequency-Psychopathology) scale consists of items that no more than 20% of two samples of psychiatric inpatients, as well as a normative sample, was endorsed in a deviant direction; it was developed to detect malingering in settings with high base rates of serious psychopathology. The FBS (Fake Bad Scale) consists of items infrequently endorsed by personal injury litigants that tap somatic rather than psychiatric symptoms. High elevations of these scales invalidate an MMPI-2 pro-file and may indicate confusion or reading problems, random responding, severe psychopathology, symptom exaggeration, or malingering. In all, if an overreporting scale is elevated, it is likely the examinee responded in a manner that exaggerated impressions of experienced psychopathology.

The two primary scales designed to detect underreporting of psychopathology are the L (Lie) and K (Correction) scales. The L scale includes items selected to identify examinees who are trying to avoid answering items honestly so as to create an overly positive impression. Because many L scale items are obvious, elevations indicate that the examinee is engaging in a psychologically unsophisticated and naive attempt to portray himself or herself as possessing high moral value, without even minor personal flaws or shortcomings that most individuals would endorse on a self-report test. Poor insight and denial of problems are likely in these individuals. K scale items were selected to assist in identifying individuals who displayed significant psychopathology yet had profiles within the normal range. Because such defensive responding masks experienced symptoms, several clinical scales (e.g., Schizophrenia) are corrected for K scale scores. K scale elevations may indicate that an examinee was being defensive, has poor insight, and may be seeking to maintain a faqade of adequacy and control without admitting to problems or weaknesses. As compared with L, the K scale assesses more sophisticated and subtle defensive responding. In addition to the L and K scales, the Wiggins’ Social Desirability Scale, with items assessing self-confidence, social skills, and effective decision making, evaluates the degree to which examinees present themselves in a positive and socially desirable fashion. A similar scale, the Superlative scale, evaluates the degree to which individuals present themselves in a superlative or highly virtuous fashion, while denying problems. As with L and K, elevations on these scales may represent defensiveness, impression management, or poor insight or awareness into one’s behavior. Overall, if an underreporting scale is elevated, it is likely the examinee approached other items in a manner that attempted to present the most favorable self-image and deny psychological difficulties.

In addition to specific measures of over- and underreporting, test users can examine various configurations and interrelations of the L, F, and K scales. An example of this is the F-K Index, also known as the Gough Dissimulation Index, for which the raw score on the K (Correction) scale is subtracted from the raw F (Infrequency) scale. Specific interpretive cut scores points are available but, generally, high scores (i.e., a significantly higher F than K) indicate overreporting of psychopathology, low scores (i.e., a significantly higher K than F) indicate underreporting of psychopathology, and intermediate scores indicate accurate item endorsement.

References:

  1. Butcher, J. N., Graham, J. R., Ben-Porath, Y. S., Tellegen, A., Dahlstrom, W. G., & Kaemmer, B. (2001). MMPI-2 (Minnesota Multiphasic Personality Inventory-2): Manual for administration, scoring, and interpretation (Rev. ed.). Minneapolis: University of Minnesota Press.
  2. Graham, J. R. (2005). MMPI-2: Assessing personality and psychopathology (4th ed.). New York: Oxford University Press.
  3. Greene, R. L. (2000). The MMPI-2: An interpretive manual (2nd ed.). Boston: Allyn & Bacon.

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