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The Evaluation of Truthfulness in Alleged Sex Offenders' Self-Reports: 16PF and MMPI Validity Scales Linda S. Grossman , Thomas W. Haywood & Orest E. Wasyliw Published online: 10 Jun 2010.
To cite this article: Linda S. Grossman , Thomas W. Haywood & Orest E. Wasyliw (1992) The Evaluation of Truthfulness in Alleged Sex Offenders' Self-Reports: 16PF and MMPI Validity Scales, Journal of Personality Assessment, 59:2, 264-275, DOI: 10.1207/s15327752jpa5902_4 To link to this article: http://dx.doi.org/10.1207/s15327752jpa5902_4
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JOURNAL OF PERSONALITY ASSESSMENT, 1992, 59(2), 264-275 Copyright o 1992, Lawrence Erlbaum Associates, Inc.
The Evaluation of Truthfulness in Alleged Sex Offenders' Self-Reports: 16PF and MMPI Validity Scales
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Linda S. Grossman Department of Psychiaf ry University of Illinois at Chicago
Thomas W. Haywood Department of Psychiatry Rush-Presbyterian-St. Luke's Medical Center
Orest E. Wasyliw Department of Psychiatry and Department of Psychology and Social Sciences Rush-Presbyterian-St. Luke's Medical Center
The evaluation of response bias (i.e., minimization or exaggeration) is central to forensic psychological evaluations. Yet few studies have assessed forensic samples to investigate the ability of psychological tests to detect response bias. We studied the relationshipbetween the Sixteen Personality Factors Questionnaire (16PF) and the Minnesota Multiphasic Personality Inventory (MMPI) validity scales for 65 alleged sex offenders and assessed the effects of different cutoff scores for the 16PF validity scales. Results indicate consistent significant correlations between the validity scales of the 16PF and the MMPI for measures of minimization and exaggeration. Use of a priori cutoff scores resulted in the classification of our sample in proportions parallel to those found in previous research for the 16PF Fake-Good scale but not the Fake-Bad scale. Our results indicate that 16PF validity scales are useful, but interpretations must take into account different base rates of response bias between sex offenders and the general population.
T h e evaluation of response bias, that is, subjects' tendency either t o describe themselves in socially desirable terms o r i n pathological terms, is necessary for the accurate interpretation of interview and psychologica1 test data i n many settings. T h e assessment of response bias is especially important in forensic psychological assessments and constitutes one of t h e unique advantages of
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psychological testing in this field. This is because in forensic evaluations, by definition, subjects generally have substantial, tangible gains either from accentuating their strengths (e.g., in employment applications or child custody disputes) or from accentuating their weaknesses (e.g., when subjects desire entrance into psychotherapy or seek an insanity defense). For this reason, psychological tests constructed with validity scales designed to detect response bias are particularly useful, and research on the effectiveness of these tests' validity scales is critical. A number of studies have been published which address the ability of various psychological tests to detect response bias or to remain impermeable to faking (Albert, Fox, & Kahn, 1980; Dubinsky, Gamble, &Rogers, 1985; Grossman & Wasyliw, 1988; Grow, McVaugh, & Eno, 1980; Heaton, Smith, Lehman, & Voyt, 1978; Irvine & Gendreau, 1974; Meredith, 1968; Rogers, 1988; Was~liw, Grossman, Haywood, & Cavanaugh, 1988). Some studies specifically focus on the detection of response bias in sex offenders (Grossman & Cavanaugh, 1989, 1990; Hall, 1989; Langevin, 1988; Lanyon, Dannenbaum, Wolf, & Brown, 1989; Lanyon & Lutz, 1984). One psychological test that offers validity scales designed to detect response bias is the Sixteen Personality Factors Questionnaire (16PF; Cattell, Eber, &L Tatsuoka, 1970). In general, validity scales are designed to assess types of exaggeration or minimization in actual clinical evaluations. However, most studies of the validity scales of the 16PF have used experimental samples, such as students instructed to fake good or fake bad while taking the test (e.g., Braun & LaFaro, 1969; Riggio, Salinas, & Tucker, 1988; Strickler, 1974; Winder, O'Dell, & Karson, 1975) or job applicants undergoing psychological screening (Birenbaum, 1986; Birenbaum & Montag, 1989; Elliott, 1976a, 197613; Kochkin, 1987). Although this experimental design is appropriate for the initial validation of these scales, such a design may produce data of limited generalizability to the clinical situations targeted by these scales (Pankratz & Erickson, 1990). There have only been a few studies on the use of the 16PF with actual forensic samples (Audubon & Kirwin, 1982; Dalby, 1988; Irvine & Gendreau, 1974; Langevin, Paitich, Freeman, Mann, & Handy, 1978; Lanyon et al., 1989), and even fewer have examined the use of the 16PF validity scalles with sex offenders. Because of the scarcity of research on the efficacy of the 16PFs validity scalles in forensic settings, little is known about their efficacy in detecting clinical patients who attempt to fake good or fake bad (Greene, 1988). For example, there have been few studies (Dalby, 1988) that have assessed the effectiveness of the 16PF in detecting response bias in forensic patients who are known to minimize or exaggerate psychopathology on the Minnesota Multiphasic Personality Inventory ( M I ; Hathaway & McKinley, 1967), which has the most widely researched and effective validity scales of any psychometric instrument (Greene, 1980, 1988; Ziskin & Faust, 1988). In addition, the 16PF literature has not produced a consensus about the best cutoff scores to use in deciding whether
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a particular profile shows significant response bias (Krug, 1978; Winder et al., 1975). The original cutoff score proposed by Winder et al. (1975) was set at 7 or higher (out of a possible 15 items per scale) for both the Motivation Distortion (fake good) and the Fake-Bad scale. Krug (1978), using a larger normative sample for cross-validation,later suggested that a score of 10 constituted a better cutoff criterion for the Fake-Good scale because this score classified 15% of his normative sample as attempting to fake good when taking the 16PF under standard instructions. Use of this rationale, however, assumes a normal distribution of response bias in the population being tested. Our study was designed to focus on the following research questions:
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1. Are the validity scales of the 16PF correlated with those of the MMPI?
2. Can optimal scores on the 16PF validity scales be generated to classify alleged sex offenders as showing fake-good or fake-bad profiles on the MMPI? 3. What proportion of alleged sex offenders are defined as faking good or faking bad by the 16PF based on a priori cutoff scores?
METHOD
Subjects The forensic sample used here comprised 65 men who were accused of having committed sexual offenses. These men were undergoing psychological evaluations at the Sexual Behaviors Clinic of the Isaac Ray Center, Inc., a universitybased outpatient evaluation and treatment center affiliated with RushPresbyterian-St. Luke's Medical Center and Rush Medical College in Chicago. Of these 65 patients, 42 faced allegations of child molestation, 12 of incest, 5 of exhibitionism, 4 of purchasing illegal child pornography, and 2 were doctors alleged to have had sex with their patients. Five of the 65 patients (approximately 8%) were incarcerated at the time of their assessment. The total sample ranged in age from 20 to 72 years, with a mean age of 41.2 years. They had completed a mean of 15 years of school (ranging from 8 to 22 years). Fifty-seven (88%) were White and 8 (12%) were minority patients. The mean total I Q score, as assessed by the Shipley Institute of Living Scale (Shipley, 1940), was 112.5 (SD = 12.9), which falls within the average range of intellectual functioning for the general population (Paulson & Lin, 1980). All patients took the 16PF and MMPI as part of their routine psychological assessments.
Procedure Form A of the 16PF and the full 566-item MMPI were administered by means of an interactive computerized assessment system described in a previous article
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(Cavanaugh, Rogers, 6r Was~liw,1982). The 16PF measures of response bias used in our study were the Fake-Bad scale and the Motivation Distortion scale. For the purposes of this study, the Motivation Distortion scale is referred to henceforth as the Fake-Good scale. The MMPI validity indices were the L, K, and F scales (Greene, 1980), the F-minus-K index (Gough, 1950), the Obviousminus-Subtle subscales (0-S; Wiener, 1948), the Gough Dissimulation scale-Revised (Ds-r; Gough, 1957), and the Positive Malingering scale (hip; Cofer, Chance, & Judson, 1949). These scales were validated as being able to discriminate honest from invalid responders among criminal patients (Grossman & Wasyliw, 1988; Wasyliw et al., 1988) and police officers undergoing fitness-for-duty evaluations (Grossman, Haywood, Ostrov, Wasyliw, & Cavanaugh, 1990). These scales were also recommended by Greene (1984,19'31) and validated by Grow et al. (1980) as being able to discriminate honest responders from experimental subjects instructed to minimize or exaggerate. An ideal research design to assess response bias in a naturalistic population is to have an independent external criterion to denote which patients are exaggerating or minimizing. However, forensic patients are not likely to admit to dissembling, and no other "gold standard" has been devised by which to detlect dissimulation. Nonetheless, an indirect psychometric approach, the MMPI, has been shown effectively to distinguish patients motivated to exaggerate or minimize and has been validated against independent external criteria (Grow et al., 1980; Lanyon & Lutz, 1984; Wasyliw et al., 1988). Therefore, we utilized MMPI validity scale scores as our criteria for the presence of response bias. Test protocols were divided into minimized and not minimized categories according to criteria suggested by Grow et al. (1980) for the F-minus-K index and the 0-S subscales. The criterion for minimization on the F-minus-K index was a raw score difference less than or equal to - 12. For the 0-S subscales, an O-S index was computed by taking the difference between the sum of the Obvious and Subtle subscale T scores for each subscale: Depression (0,Somatization and Repression 0, Conflict With Authority and Antisocial Attitudes (F'd), Suspiciousness (Pa), and Hypomanic Features (Ma). Previous research has shown that minimization can be discriminated through a relative elevation of Subtle subscale scores as compared to corresponding Obvious subscale scores, and exaggeration of psychopathology or malingering can be detected by the opposite pattern (Anthony, 1971; Burkhart, Christian, & Gynther, 1978; Griow et al., 1980; Wiener, 1948). The criterion for minimization for the 0-S index was a difference less than or equal to - 11 (Greene, 1984). Protocols were categorized as minimized if patients' scores fell below cutoff scores on both the F-minw-K index and the 0-S index. To categorize patients according to whether they showed evidence of ex,aggeration on the MMPI, the Ds-r scale was used. This scale is particularly appropriate because it is sensitive to exaggeration or overstatement of neurotic symptoms rather than symptoms of more severe psychopathology such as
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psychosis. Because the 16PF is predominantly a test of personality features rather than a test of severe psychopathology, the type of symptoms that are most likely to be exaggerated by sex offenderson this test may be more closely aligned to the neurotic symptoms represented specifically by the Ds-r scale than to the more severe symptoms reflected in the item content of the other MMPI validity scales. Because previous research (Grossman & Cavanaugh, 1989,1990)showed that even moderate exaggeration is rare among alleged sex offenders, and thar the equivocal range of exaggeration on the Ds-r scale effectively detected malingering in a criminal sample (Wasyliw et al., 1988), we used a Ds-r cutoff score greater than or equal to 61, which is the cutoff for the equivocal range of exaggeration (Greene, 1984). To exclude random responders, patients' test protocols were not used if their 16PF Randomness scale score exceeded 5 or their MMPI Test-Retest or Carelessness scale scores exceeded 5 (Greene, 1978, 1979; Karson & O'Dell, 1976; O'Dell, 1971; Rogers, 1983).Thii procedure also helped to ensure that test items were understood by all subjects. Seven subjects were excluded from the study on this basis.
RESULTS
Correlations Between the Validity Scales of the 16PF and MMPI To investigate whether the validity scales of the 16PF are associated with those of the MMPI, we calculated a series of correlations between the Fake-Good and Fake-Bad scales of the 16PF with each of the MMPI validity scales. Table 1 reports the data for these analyses. The data in Table 1 indicate that there were significant correlations between the validity scales of the 16PF and all but one of the validity scales of the MMPI. TABLE 1 Correlations Between 16PF and MMPI Validity Scales MMPI Validity Scale
L F K F-K MP Ds-r 0-S
*p
< .05. **p < .OOl.
16PF Fake-Good Scale
16PF Fake-Bad Scale
.38** - .42** .51** - .52** .64** - .57** - .59**
- .01 .47** - .28* .41** - .21* .36** .38**
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The only exception was that there was no correlation between the 16PF Fake-Bad scale and the MMPI L scale. In other words, there was no associati~on between attempting to appear dysfunctional (16PF) and admitting or denying basic human faults or limitations (MMPI L scale). In all other cases, the direction of the correlations were such that exaggeration on the 16PF was associated with exaggeration on the MMPI, and minimization on the 16PF was associated with minimization on the MMPI. To provide further information about the frequency of minimization and exaggeration as assessed both by the 16PF and the MMPP, we analyzed patients' scores on the Fake-Good and Fake-Bad scales of the 16PF according to whether or not patients showed evidence either of minimizing or exaggerating on the MMPI. Table 2 which presents these analyses, indicates that only 17% of 1:he patients whose scores on the 16PF Fake-Good scale were very low (i.e., not minimized) showed evidence of minimization on the MMPI. In contrast, 73X1of patients with a moderate score ranging from 7 to 10 on the 16PF Fake-Good scale showed evidence of minimization on the MMPI, as did 80% of patients scoring 11 or higher on the 16PF Fake-Good scale. This represents a higlhly significant relationship between minimization on the 16PF and MMPI, X2(2)= 21.60, P < .0001. The mean score on the Fake-Good scale was 7.18 (SD = 2.95), which is similar to that found in previous normative research (Krug, 1978). The data on the Fake-Bad scale indicate that 24% of patients scoring 2 or less on this scale showed evidence of exaggerating on the MMPI. Thirty-two percent of patients scoring 3 or 4 on this scale showed evidence of exaggerating on the MMM, as did 67% of patients scoring 5 or 6 on this scale. No patient had a IWF TABLE 2 Percentage of Patients With Various Levels of Response Bias on the 16PF Who Showed Evidence of Res~onseBias on the MMPI 16PF Validity Scale
MMPI Validity Scale
16PF Fake-Good Scorea Category
Range
n
Not Minimized
Minimized
Low Moderate High
0-6 7-10 211
29 26 10
24 83% 7 27% 2 20%
5 17% 19 73% 8 80%
Not Exaggernted
Exaggerated
16PF Fake-Bad Scoreb Low Moderate High
0-2 3-4 5-6
37 19 9
28 76% 13 68% 3 33%
-
9 241% 6 3i:% 6 67%
-
Note. N = 65. "x2(2)= 21.60, p < .0001; M = 7.18; SD = 2.95. bx2(2)= 5.94, p < .05; M = 2.48; SD = 1.62.
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Fake-Bad scale score greater than 6. Again, this represents a significant relationship between exaggeration on the 16PF and the MMPI, X2(2)= 5.94, p < .05, despite a restricted range of 16PF Fake-Bad scores. The patients' mean score on this scale was 2.48 (SD = 1.62). Again, this mean score is similar to that found by Krug (1978).
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Efficacy of the 16PF in Predicting MMPI Minimization and Exaggeration To determine whether patients' scores on the 16PF could be used to classify patients as showing fake-good or fake-bad profiles on the MMPI, we conducted a set of discriminant function analyses. We first used the 16PF Fake-Good scale to predict classification in the minimized or not minimized category, using as criteria for minimization low scores on both the F-minus-K index and the O-S index (F-minus-Kraw score 5 - 12 and sum of O-S T scores 5 11). The cutoff score for the Fake-Good scale generated by this analysis was 8, which correctly classified 72% of the cases (Wilks's Lambda = .72, p < .0001). Next we conducted the same analysis using the 16PF Fake-Bad scale to predict classification in the exaggerated and not exaggerated category, as determined by the Ds-r scale (Tscore > 61). O n this analysis, a cutoff score of 3 correctly classified 62% of the cases (Wilks's Lambda = .92, P < .02).
16PF Fake-Good and Fake-Bad Cutoff Scores Table 3 presents the frequency distribution and cumulative percentages of individuals from our sample whose scores fell beneath each of the cutoff scores for both minimization and exaggeration,proposed by previous researchers. The data on minimization allowed the comparison of the two cutoff scores: a score of 7 or greater, which was suggested by Winder et al. (1975); and a score of 10 or greater, which was suggested by Krug (1978). TABLE 3 Number and Percentages of Patients Classified as Faking on the 16PF Using Various Cutoff Scores Cutoff Score for Faking Good on the 16PF
r7 r 10 211 Cutoff Score for Faking Bad on the 16PF
n and % Classified as Faking Good
36 12 10
55% 18% 15%
n a d % Classified as Faking Bad
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The data in Table 3 indicate that for our sample of alleged sex offenders, the cutoff score greater than or equal to 7, which was suggested by the original study (Winder et al., 1975), classified 55% of the sample as minimizing problems or emotional difficulties. The cutoff score greater than or equal to 10 classified 18%of the sample as showing evidence of minimization. A cutoff score greater than or equal to 11 classified 15% of the sample as showing evidence of minimization. In regard to exaggeration, none of our subjects scored at or above the cutoff score of 7 or greater proposed by both Winder et al. (1975) and by Krug (1978). Thus, this sample did not show strong tendencies to exaggerate their personal weaknesses on the 16PF. In our sample, 69% fell at or above a Fake-Bad score of 3,26% fell at or above 4, and 14% fell at or above 5.
DISCUSSION The assessment of response bias is crucial to forensic psychological evaluations because subjects' involvement with the law creates situations that may motivate them to attempt to appear either as more or less psychologically disturbed than may actually be the case. The evaluation of patients' veracity of self-report is central in such cases both because of the frequency with which patients attempt to distort their evaluations in forensic settings (Grossman & Was~liw,1988; Grossman et al., 1990; Lanyon & Lutz, 1984; Wasyliw et al., 1988) and because of the importance of considering response bias in the interpretation of cliniical material. Despite this importance, there have been very few studies that have investigated the validity scales of major psychological tests using actual forensic samples. Our study focuses on the validity scales of the 16PF. Specifically, we assessed the correspondence of 16PF validity scales to the MMPI validity scales in classifying response bias in a sample of alleged sex offenders undergoing forensic psychological evaluations. First, we investigated the potential relationship between the 16PF validity scales and those of the MMPI. Note that the meaning of response bias may be different for the 16PF and MMPI due to differences in overall test design and item content. The 16PF is primarily designed in the form of an attitude and opinion questionnaire, with items assessing personality characteristics rather than psychopathology, whereas the MMPI is composed largely of items assessing symptoms of psychopathology. Thus exaggeration on the 16PF indicates endorsement of personality attributes that are commonly viewed as socially undesirable though not necessarily pathological, whereas exaggeration on the MMPI indicates overstatement of symptoms of emotional distress or mental disorder. This pattern is supported by Lanyon et al. (1989) who have concluded that faking good and faking bad do not represent endpoints of a single unitary dimension, but rather can be viewed as independent and distinct (orthogonal) concepts. Thus it is possible for the same individual to show minimization on the
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16PF and exaggeration on the MMPI. Such an individual would respond as if claiming he or she were the innocent victim of a mental disorder which could not be controlled and which would be to blame for the individual's problem behavior, and the individual would deny any objectionable personality traits or beliefs. This argument suggests that the presence of exaggeration should be interpreted differently for the two scales. In contrast, minimization on the 16PF and MMPI both indicate denial of deviant or undesirable characteristics. Despite these differences, our data showed consistent significant correlations between the validity scales of both tests. Minimization on the 16PF was significantly associated with minimization on the MMPI, and exaggeration on the 16PF was significantly associated with exaggeration on the MMPI. Furthermore, the vast majority of patients with low scores on the 16PF Fake-Good scale showed no minimization on the MMPI, whereas the vast majority of patients with moderate to high Fake-Good scale scores showed evidence of minimization on the MMPI. Similarly, more than three quarters of the patients with low scores on the 16PF Fake-Bad scale showed no evidence of exaggeration on the MMPI, whereas two thirds of the patients with moderate or higher Fake-Bad scale scores exaggerated on the MMPI. These results suggest a high degree of consistency between the two sets of validity scales. Next we compared the effects of various 16PF cutoff scores on the distribution of response bias in our population. We conducted a discriminant function analysis to predict minimized versus nonminimized and exaggerated versus nonexaggerated groups using MMPI validity scale scores as criterion measures. Discriminant function analysis generated a cutoff score of 8 for the Fake-Good scale and a cutoff score of 3 for the Fake-Bad scale. Furthermore, we found that a cutoff score of greater than or equal to 11 for the Fake-Good scale and greater than or equal to 5 for the Fake-Bad scale classified about 15% of our sample as showing evidence of response bias, which corresponds to the proportions found by Krug (1978). However, Krug's assumption of a normal distribution of response bias is not likely to be valid for sex offender populations. O n the basis of the MMPI alone, in our sample, we found a high prevalence of minimization and a much lower prevalence of extreme exaggeration, which conforms to previous research (Lanyon et al., 1989). The predominance of minimization in our sample may have been caused by patients' belief that admission of psychopathology would constitute a confession of behavioral deviations, which will support the impression that they indeed could have committed the alleged sexual offenses. Previous research has shown that alleged male sex offenders are far more likely to minimize than to exaggerate psychopathology or personal limitations (Grossman & Cavanaugh, 1989, 1990; Lanyon et al., 1989). This pattern, which was also obtained using our sample, may reflect a lower base rate of exaggeration for sex offenders in general than for other clinical populations. If this is true, even moderate elevations on the Fake-Bad scale may denote unusual patterns of responding for this population and may
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warrant further inquiry. This finding also raises the possibility that a lower cutoff score for the Fake-Bad scale may be appropriate for alleged sex offenders. Our sample is also likely to have a higher rate of minimization than does the general population. Moderate minimization may reflect an appropriate and rational assessment of the circumstances of testing in that the subject is trying to create a positive impression. Therefore, a higher Fake-Good scale cutoff score may be desirable in determining whether a subject is intentionally presentinlg a false self-report on this instrument. Note that Krug (1978) suggested a cutoff score of 10 for the Fake-Good scale because it classified 15% of his population as minimizing. This relies on two assumptions that may be questionable: Most individuals will be honest when filling out a questionnaire asking about a great variety of their personal traits and attitudes, and response bias will be norma~lly distributed in a given patient population. Further research is needed to determine optimal cutoff scores for sex offender populations. Our research addresses the use of the 16PF validity scales in forensic psychological evaluations of alleged sex offenders. Validity scales of the 16PF were significantly correlated with those of the MMPI and correctly predicted a high percentage of patients who showed minimization and exaggeration on the MMPI. Our study also supports prior findings that minimization is far more common among sex offenders than exaggeration, in comparison to nornnal populations. These data should be valuable to psychologists who conduct forensic evaluations in which patients may be motivated to distort their self-presentations.
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malingering and deception (pp. 269-290). New York: Guilford. Langevin, R., Paitich, D., Freeman, R., Mann, K., & Handy, L. (1978). Personality characteristics and sexual anomalies in males. Canadian Journal of Behavioral Science, 10, 222-238. Lanyon, R. I., Dannenbaum, S. E., Wolf, L. L., & Brown, A. (1989). Dimensions of deceptive responding in criminal offenders. Psychological Assessment: A Journal of Consulting and Clinical Psychology, 1,300-304. Lanyon, R. I., & Lutz, R. W. (1984). MMPI discrimination of defensive and nondefensivefelony sex offenders. Journal of Cwulting and Clinical Psychology, 52,841-843. Meredith, G. M. (1968). Stereotypic desirability profiles for the 16PF questionnaire. Psychological Reports, 23, 1173-1 174. O'Dell, J. W. (1971). Method for detecting random answers on personality questionnaires. Journal of Applied Psychology,55,380-383. Pankratz, L., & Erickson, R. C . (1990). Two views of malingering. The Clinical Neuropsychologist, 4, 379-389. Paulson, M. J., & Lin, T. (1980). Predicting WAIS I Q from Shipley-Hartford scores. Journal of Clinical Psychology, 26,453-461. Riggio, R. E., Salinas, C., 6r Tucker, J. (1988). Personality and deception ability. Personality (and Individual Differences, 9, 189-191. Rogers, R. (1983). Malingering or random? A research note on Obvious vs. Subtle subscales of the MMPI. Journal of Clinical Psychology, 39, 257-258. Rogers, R. (1988). Clinical assessment of malingering and deception. New York: Guilford. Shipley, W. C . (1940). A self-administered scale for measuring intellectual impairment and deterioration. Journal of Psychology, 9,371-377. Stricker, L. J. (1974). Response styles and 16PF higher order factors. Educational and Psychological Measurement, 34, 295-313. Wasyliw, 0. E., Grossman, L. S., Haywood, T. W., & Cavanaugh, J. L. (1988). The detection of malingering in criminal forensic groups: MMPI validity scales. Journal of Personality Assessment, 52, 321-333. Wiener, D. W. (1948). Subtle and obvious keys for the Minnesota Multiphasic Personality Inventory. Journal of Consulting Psychology, 12, 164-170. Winder, P., O'Dell, J. W., & Karson, S. (1975). New motivational distortion scales for the 16PF. Journal of P e r s d i t y Assessment, 39, 532-537. Ziskin, J., & Faust, D. (1988). Challenging the assessment of malingering or credibility. In J. Zirkin & D. Faust (Eds.), Coping with psychiatric and psychological testimony (pp. 850-876). Marina del Rey, CA: Law and Psychology Press.
Linda S. Grossman Department of Psychiatry University of Illinois at Chicago 912 South Wood Street, M/C 913 Chicago, IL 60612 Received July 22, 1991 Revised October 3 1, 1991
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The Evaluation of Truthfulness in Alleged Sex Offenders' Self-Reports: 16PF and MMPI Validity Scales Linda S. Grossman , Thomas W. Haywood & Orest E. Wasyliw Published online: 10 Jun 2010.
To cite this article: Linda S. Grossman , Thomas W. Haywood & Orest E. Wasyliw (1992) The Evaluation of Truthfulness in Alleged Sex Offenders' Self-Reports: 16PF and MMPI Validity Scales, Journal of Personality Assessment, 59:2, 264-275, DOI: 10.1207/s15327752jpa5902_4 To link to this article: http://dx.doi.org/10.1207/s15327752jpa5902_4
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JOURNAL OF PERSONALITY ASSESSMENT, 1992, 59(2), 264-275 Copyright o 1992, Lawrence Erlbaum Associates, Inc.
The Evaluation of Truthfulness in Alleged Sex Offenders' Self-Reports: 16PF and MMPI Validity Scales
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Linda S. Grossman Department of Psychiaf ry University of Illinois at Chicago
Thomas W. Haywood Department of Psychiatry Rush-Presbyterian-St. Luke's Medical Center
Orest E. Wasyliw Department of Psychiatry and Department of Psychology and Social Sciences Rush-Presbyterian-St. Luke's Medical Center
The evaluation of response bias (i.e., minimization or exaggeration) is central to forensic psychological evaluations. Yet few studies have assessed forensic samples to investigate the ability of psychological tests to detect response bias. We studied the relationshipbetween the Sixteen Personality Factors Questionnaire (16PF) and the Minnesota Multiphasic Personality Inventory (MMPI) validity scales for 65 alleged sex offenders and assessed the effects of different cutoff scores for the 16PF validity scales. Results indicate consistent significant correlations between the validity scales of the 16PF and the MMPI for measures of minimization and exaggeration. Use of a priori cutoff scores resulted in the classification of our sample in proportions parallel to those found in previous research for the 16PF Fake-Good scale but not the Fake-Bad scale. Our results indicate that 16PF validity scales are useful, but interpretations must take into account different base rates of response bias between sex offenders and the general population.
T h e evaluation of response bias, that is, subjects' tendency either t o describe themselves in socially desirable terms o r i n pathological terms, is necessary for the accurate interpretation of interview and psychologica1 test data i n many settings. T h e assessment of response bias is especially important in forensic psychological assessments and constitutes one of t h e unique advantages of
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psychological testing in this field. This is because in forensic evaluations, by definition, subjects generally have substantial, tangible gains either from accentuating their strengths (e.g., in employment applications or child custody disputes) or from accentuating their weaknesses (e.g., when subjects desire entrance into psychotherapy or seek an insanity defense). For this reason, psychological tests constructed with validity scales designed to detect response bias are particularly useful, and research on the effectiveness of these tests' validity scales is critical. A number of studies have been published which address the ability of various psychological tests to detect response bias or to remain impermeable to faking (Albert, Fox, & Kahn, 1980; Dubinsky, Gamble, &Rogers, 1985; Grossman & Wasyliw, 1988; Grow, McVaugh, & Eno, 1980; Heaton, Smith, Lehman, & Voyt, 1978; Irvine & Gendreau, 1974; Meredith, 1968; Rogers, 1988; Was~liw, Grossman, Haywood, & Cavanaugh, 1988). Some studies specifically focus on the detection of response bias in sex offenders (Grossman & Cavanaugh, 1989, 1990; Hall, 1989; Langevin, 1988; Lanyon, Dannenbaum, Wolf, & Brown, 1989; Lanyon & Lutz, 1984). One psychological test that offers validity scales designed to detect response bias is the Sixteen Personality Factors Questionnaire (16PF; Cattell, Eber, &L Tatsuoka, 1970). In general, validity scales are designed to assess types of exaggeration or minimization in actual clinical evaluations. However, most studies of the validity scales of the 16PF have used experimental samples, such as students instructed to fake good or fake bad while taking the test (e.g., Braun & LaFaro, 1969; Riggio, Salinas, & Tucker, 1988; Strickler, 1974; Winder, O'Dell, & Karson, 1975) or job applicants undergoing psychological screening (Birenbaum, 1986; Birenbaum & Montag, 1989; Elliott, 1976a, 197613; Kochkin, 1987). Although this experimental design is appropriate for the initial validation of these scales, such a design may produce data of limited generalizability to the clinical situations targeted by these scales (Pankratz & Erickson, 1990). There have only been a few studies on the use of the 16PF with actual forensic samples (Audubon & Kirwin, 1982; Dalby, 1988; Irvine & Gendreau, 1974; Langevin, Paitich, Freeman, Mann, & Handy, 1978; Lanyon et al., 1989), and even fewer have examined the use of the 16PF validity scalles with sex offenders. Because of the scarcity of research on the efficacy of the 16PFs validity scalles in forensic settings, little is known about their efficacy in detecting clinical patients who attempt to fake good or fake bad (Greene, 1988). For example, there have been few studies (Dalby, 1988) that have assessed the effectiveness of the 16PF in detecting response bias in forensic patients who are known to minimize or exaggerate psychopathology on the Minnesota Multiphasic Personality Inventory ( M I ; Hathaway & McKinley, 1967), which has the most widely researched and effective validity scales of any psychometric instrument (Greene, 1980, 1988; Ziskin & Faust, 1988). In addition, the 16PF literature has not produced a consensus about the best cutoff scores to use in deciding whether
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a particular profile shows significant response bias (Krug, 1978; Winder et al., 1975). The original cutoff score proposed by Winder et al. (1975) was set at 7 or higher (out of a possible 15 items per scale) for both the Motivation Distortion (fake good) and the Fake-Bad scale. Krug (1978), using a larger normative sample for cross-validation,later suggested that a score of 10 constituted a better cutoff criterion for the Fake-Good scale because this score classified 15% of his normative sample as attempting to fake good when taking the 16PF under standard instructions. Use of this rationale, however, assumes a normal distribution of response bias in the population being tested. Our study was designed to focus on the following research questions:
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1. Are the validity scales of the 16PF correlated with those of the MMPI?
2. Can optimal scores on the 16PF validity scales be generated to classify alleged sex offenders as showing fake-good or fake-bad profiles on the MMPI? 3. What proportion of alleged sex offenders are defined as faking good or faking bad by the 16PF based on a priori cutoff scores?
METHOD
Subjects The forensic sample used here comprised 65 men who were accused of having committed sexual offenses. These men were undergoing psychological evaluations at the Sexual Behaviors Clinic of the Isaac Ray Center, Inc., a universitybased outpatient evaluation and treatment center affiliated with RushPresbyterian-St. Luke's Medical Center and Rush Medical College in Chicago. Of these 65 patients, 42 faced allegations of child molestation, 12 of incest, 5 of exhibitionism, 4 of purchasing illegal child pornography, and 2 were doctors alleged to have had sex with their patients. Five of the 65 patients (approximately 8%) were incarcerated at the time of their assessment. The total sample ranged in age from 20 to 72 years, with a mean age of 41.2 years. They had completed a mean of 15 years of school (ranging from 8 to 22 years). Fifty-seven (88%) were White and 8 (12%) were minority patients. The mean total I Q score, as assessed by the Shipley Institute of Living Scale (Shipley, 1940), was 112.5 (SD = 12.9), which falls within the average range of intellectual functioning for the general population (Paulson & Lin, 1980). All patients took the 16PF and MMPI as part of their routine psychological assessments.
Procedure Form A of the 16PF and the full 566-item MMPI were administered by means of an interactive computerized assessment system described in a previous article
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(Cavanaugh, Rogers, 6r Was~liw,1982). The 16PF measures of response bias used in our study were the Fake-Bad scale and the Motivation Distortion scale. For the purposes of this study, the Motivation Distortion scale is referred to henceforth as the Fake-Good scale. The MMPI validity indices were the L, K, and F scales (Greene, 1980), the F-minus-K index (Gough, 1950), the Obviousminus-Subtle subscales (0-S; Wiener, 1948), the Gough Dissimulation scale-Revised (Ds-r; Gough, 1957), and the Positive Malingering scale (hip; Cofer, Chance, & Judson, 1949). These scales were validated as being able to discriminate honest from invalid responders among criminal patients (Grossman & Wasyliw, 1988; Wasyliw et al., 1988) and police officers undergoing fitness-for-duty evaluations (Grossman, Haywood, Ostrov, Wasyliw, & Cavanaugh, 1990). These scales were also recommended by Greene (1984,19'31) and validated by Grow et al. (1980) as being able to discriminate honest responders from experimental subjects instructed to minimize or exaggerate. An ideal research design to assess response bias in a naturalistic population is to have an independent external criterion to denote which patients are exaggerating or minimizing. However, forensic patients are not likely to admit to dissembling, and no other "gold standard" has been devised by which to detlect dissimulation. Nonetheless, an indirect psychometric approach, the MMPI, has been shown effectively to distinguish patients motivated to exaggerate or minimize and has been validated against independent external criteria (Grow et al., 1980; Lanyon & Lutz, 1984; Wasyliw et al., 1988). Therefore, we utilized MMPI validity scale scores as our criteria for the presence of response bias. Test protocols were divided into minimized and not minimized categories according to criteria suggested by Grow et al. (1980) for the F-minus-K index and the 0-S subscales. The criterion for minimization on the F-minus-K index was a raw score difference less than or equal to - 12. For the 0-S subscales, an O-S index was computed by taking the difference between the sum of the Obvious and Subtle subscale T scores for each subscale: Depression (0,Somatization and Repression 0, Conflict With Authority and Antisocial Attitudes (F'd), Suspiciousness (Pa), and Hypomanic Features (Ma). Previous research has shown that minimization can be discriminated through a relative elevation of Subtle subscale scores as compared to corresponding Obvious subscale scores, and exaggeration of psychopathology or malingering can be detected by the opposite pattern (Anthony, 1971; Burkhart, Christian, & Gynther, 1978; Griow et al., 1980; Wiener, 1948). The criterion for minimization for the 0-S index was a difference less than or equal to - 11 (Greene, 1984). Protocols were categorized as minimized if patients' scores fell below cutoff scores on both the F-minw-K index and the 0-S index. To categorize patients according to whether they showed evidence of ex,aggeration on the MMPI, the Ds-r scale was used. This scale is particularly appropriate because it is sensitive to exaggeration or overstatement of neurotic symptoms rather than symptoms of more severe psychopathology such as
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psychosis. Because the 16PF is predominantly a test of personality features rather than a test of severe psychopathology, the type of symptoms that are most likely to be exaggerated by sex offenderson this test may be more closely aligned to the neurotic symptoms represented specifically by the Ds-r scale than to the more severe symptoms reflected in the item content of the other MMPI validity scales. Because previous research (Grossman & Cavanaugh, 1989,1990)showed that even moderate exaggeration is rare among alleged sex offenders, and thar the equivocal range of exaggeration on the Ds-r scale effectively detected malingering in a criminal sample (Wasyliw et al., 1988), we used a Ds-r cutoff score greater than or equal to 61, which is the cutoff for the equivocal range of exaggeration (Greene, 1984). To exclude random responders, patients' test protocols were not used if their 16PF Randomness scale score exceeded 5 or their MMPI Test-Retest or Carelessness scale scores exceeded 5 (Greene, 1978, 1979; Karson & O'Dell, 1976; O'Dell, 1971; Rogers, 1983).Thii procedure also helped to ensure that test items were understood by all subjects. Seven subjects were excluded from the study on this basis.
RESULTS
Correlations Between the Validity Scales of the 16PF and MMPI To investigate whether the validity scales of the 16PF are associated with those of the MMPI, we calculated a series of correlations between the Fake-Good and Fake-Bad scales of the 16PF with each of the MMPI validity scales. Table 1 reports the data for these analyses. The data in Table 1 indicate that there were significant correlations between the validity scales of the 16PF and all but one of the validity scales of the MMPI. TABLE 1 Correlations Between 16PF and MMPI Validity Scales MMPI Validity Scale
L F K F-K MP Ds-r 0-S
*p
< .05. **p < .OOl.
16PF Fake-Good Scale
16PF Fake-Bad Scale
.38** - .42** .51** - .52** .64** - .57** - .59**
- .01 .47** - .28* .41** - .21* .36** .38**
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The only exception was that there was no correlation between the 16PF Fake-Bad scale and the MMPI L scale. In other words, there was no associati~on between attempting to appear dysfunctional (16PF) and admitting or denying basic human faults or limitations (MMPI L scale). In all other cases, the direction of the correlations were such that exaggeration on the 16PF was associated with exaggeration on the MMPI, and minimization on the 16PF was associated with minimization on the MMPI. To provide further information about the frequency of minimization and exaggeration as assessed both by the 16PF and the MMPP, we analyzed patients' scores on the Fake-Good and Fake-Bad scales of the 16PF according to whether or not patients showed evidence either of minimizing or exaggerating on the MMPI. Table 2 which presents these analyses, indicates that only 17% of 1:he patients whose scores on the 16PF Fake-Good scale were very low (i.e., not minimized) showed evidence of minimization on the MMPI. In contrast, 73X1of patients with a moderate score ranging from 7 to 10 on the 16PF Fake-Good scale showed evidence of minimization on the MMPI, as did 80% of patients scoring 11 or higher on the 16PF Fake-Good scale. This represents a higlhly significant relationship between minimization on the 16PF and MMPI, X2(2)= 21.60, P < .0001. The mean score on the Fake-Good scale was 7.18 (SD = 2.95), which is similar to that found in previous normative research (Krug, 1978). The data on the Fake-Bad scale indicate that 24% of patients scoring 2 or less on this scale showed evidence of exaggerating on the MMPI. Thirty-two percent of patients scoring 3 or 4 on this scale showed evidence of exaggerating on the MMM, as did 67% of patients scoring 5 or 6 on this scale. No patient had a IWF TABLE 2 Percentage of Patients With Various Levels of Response Bias on the 16PF Who Showed Evidence of Res~onseBias on the MMPI 16PF Validity Scale
MMPI Validity Scale
16PF Fake-Good Scorea Category
Range
n
Not Minimized
Minimized
Low Moderate High
0-6 7-10 211
29 26 10
24 83% 7 27% 2 20%
5 17% 19 73% 8 80%
Not Exaggernted
Exaggerated
16PF Fake-Bad Scoreb Low Moderate High
0-2 3-4 5-6
37 19 9
28 76% 13 68% 3 33%
-
9 241% 6 3i:% 6 67%
-
Note. N = 65. "x2(2)= 21.60, p < .0001; M = 7.18; SD = 2.95. bx2(2)= 5.94, p < .05; M = 2.48; SD = 1.62.
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Fake-Bad scale score greater than 6. Again, this represents a significant relationship between exaggeration on the 16PF and the MMPI, X2(2)= 5.94, p < .05, despite a restricted range of 16PF Fake-Bad scores. The patients' mean score on this scale was 2.48 (SD = 1.62). Again, this mean score is similar to that found by Krug (1978).
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Efficacy of the 16PF in Predicting MMPI Minimization and Exaggeration To determine whether patients' scores on the 16PF could be used to classify patients as showing fake-good or fake-bad profiles on the MMPI, we conducted a set of discriminant function analyses. We first used the 16PF Fake-Good scale to predict classification in the minimized or not minimized category, using as criteria for minimization low scores on both the F-minus-K index and the O-S index (F-minus-Kraw score 5 - 12 and sum of O-S T scores 5 11). The cutoff score for the Fake-Good scale generated by this analysis was 8, which correctly classified 72% of the cases (Wilks's Lambda = .72, p < .0001). Next we conducted the same analysis using the 16PF Fake-Bad scale to predict classification in the exaggerated and not exaggerated category, as determined by the Ds-r scale (Tscore > 61). O n this analysis, a cutoff score of 3 correctly classified 62% of the cases (Wilks's Lambda = .92, P < .02).
16PF Fake-Good and Fake-Bad Cutoff Scores Table 3 presents the frequency distribution and cumulative percentages of individuals from our sample whose scores fell beneath each of the cutoff scores for both minimization and exaggeration,proposed by previous researchers. The data on minimization allowed the comparison of the two cutoff scores: a score of 7 or greater, which was suggested by Winder et al. (1975); and a score of 10 or greater, which was suggested by Krug (1978). TABLE 3 Number and Percentages of Patients Classified as Faking on the 16PF Using Various Cutoff Scores Cutoff Score for Faking Good on the 16PF
r7 r 10 211 Cutoff Score for Faking Bad on the 16PF
n and % Classified as Faking Good
36 12 10
55% 18% 15%
n a d % Classified as Faking Bad
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The data in Table 3 indicate that for our sample of alleged sex offenders, the cutoff score greater than or equal to 7, which was suggested by the original study (Winder et al., 1975), classified 55% of the sample as minimizing problems or emotional difficulties. The cutoff score greater than or equal to 10 classified 18%of the sample as showing evidence of minimization. A cutoff score greater than or equal to 11 classified 15% of the sample as showing evidence of minimization. In regard to exaggeration, none of our subjects scored at or above the cutoff score of 7 or greater proposed by both Winder et al. (1975) and by Krug (1978). Thus, this sample did not show strong tendencies to exaggerate their personal weaknesses on the 16PF. In our sample, 69% fell at or above a Fake-Bad score of 3,26% fell at or above 4, and 14% fell at or above 5.
DISCUSSION The assessment of response bias is crucial to forensic psychological evaluations because subjects' involvement with the law creates situations that may motivate them to attempt to appear either as more or less psychologically disturbed than may actually be the case. The evaluation of patients' veracity of self-report is central in such cases both because of the frequency with which patients attempt to distort their evaluations in forensic settings (Grossman & Was~liw,1988; Grossman et al., 1990; Lanyon & Lutz, 1984; Wasyliw et al., 1988) and because of the importance of considering response bias in the interpretation of cliniical material. Despite this importance, there have been very few studies that have investigated the validity scales of major psychological tests using actual forensic samples. Our study focuses on the validity scales of the 16PF. Specifically, we assessed the correspondence of 16PF validity scales to the MMPI validity scales in classifying response bias in a sample of alleged sex offenders undergoing forensic psychological evaluations. First, we investigated the potential relationship between the 16PF validity scales and those of the MMPI. Note that the meaning of response bias may be different for the 16PF and MMPI due to differences in overall test design and item content. The 16PF is primarily designed in the form of an attitude and opinion questionnaire, with items assessing personality characteristics rather than psychopathology, whereas the MMPI is composed largely of items assessing symptoms of psychopathology. Thus exaggeration on the 16PF indicates endorsement of personality attributes that are commonly viewed as socially undesirable though not necessarily pathological, whereas exaggeration on the MMPI indicates overstatement of symptoms of emotional distress or mental disorder. This pattern is supported by Lanyon et al. (1989) who have concluded that faking good and faking bad do not represent endpoints of a single unitary dimension, but rather can be viewed as independent and distinct (orthogonal) concepts. Thus it is possible for the same individual to show minimization on the
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16PF and exaggeration on the MMPI. Such an individual would respond as if claiming he or she were the innocent victim of a mental disorder which could not be controlled and which would be to blame for the individual's problem behavior, and the individual would deny any objectionable personality traits or beliefs. This argument suggests that the presence of exaggeration should be interpreted differently for the two scales. In contrast, minimization on the 16PF and MMPI both indicate denial of deviant or undesirable characteristics. Despite these differences, our data showed consistent significant correlations between the validity scales of both tests. Minimization on the 16PF was significantly associated with minimization on the MMPI, and exaggeration on the 16PF was significantly associated with exaggeration on the MMPI. Furthermore, the vast majority of patients with low scores on the 16PF Fake-Good scale showed no minimization on the MMPI, whereas the vast majority of patients with moderate to high Fake-Good scale scores showed evidence of minimization on the MMPI. Similarly, more than three quarters of the patients with low scores on the 16PF Fake-Bad scale showed no evidence of exaggeration on the MMPI, whereas two thirds of the patients with moderate or higher Fake-Bad scale scores exaggerated on the MMPI. These results suggest a high degree of consistency between the two sets of validity scales. Next we compared the effects of various 16PF cutoff scores on the distribution of response bias in our population. We conducted a discriminant function analysis to predict minimized versus nonminimized and exaggerated versus nonexaggerated groups using MMPI validity scale scores as criterion measures. Discriminant function analysis generated a cutoff score of 8 for the Fake-Good scale and a cutoff score of 3 for the Fake-Bad scale. Furthermore, we found that a cutoff score of greater than or equal to 11 for the Fake-Good scale and greater than or equal to 5 for the Fake-Bad scale classified about 15% of our sample as showing evidence of response bias, which corresponds to the proportions found by Krug (1978). However, Krug's assumption of a normal distribution of response bias is not likely to be valid for sex offender populations. O n the basis of the MMPI alone, in our sample, we found a high prevalence of minimization and a much lower prevalence of extreme exaggeration, which conforms to previous research (Lanyon et al., 1989). The predominance of minimization in our sample may have been caused by patients' belief that admission of psychopathology would constitute a confession of behavioral deviations, which will support the impression that they indeed could have committed the alleged sexual offenses. Previous research has shown that alleged male sex offenders are far more likely to minimize than to exaggerate psychopathology or personal limitations (Grossman & Cavanaugh, 1989, 1990; Lanyon et al., 1989). This pattern, which was also obtained using our sample, may reflect a lower base rate of exaggeration for sex offenders in general than for other clinical populations. If this is true, even moderate elevations on the Fake-Bad scale may denote unusual patterns of responding for this population and may
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warrant further inquiry. This finding also raises the possibility that a lower cutoff score for the Fake-Bad scale may be appropriate for alleged sex offenders. Our sample is also likely to have a higher rate of minimization than does the general population. Moderate minimization may reflect an appropriate and rational assessment of the circumstances of testing in that the subject is trying to create a positive impression. Therefore, a higher Fake-Good scale cutoff score may be desirable in determining whether a subject is intentionally presentinlg a false self-report on this instrument. Note that Krug (1978) suggested a cutoff score of 10 for the Fake-Good scale because it classified 15% of his population as minimizing. This relies on two assumptions that may be questionable: Most individuals will be honest when filling out a questionnaire asking about a great variety of their personal traits and attitudes, and response bias will be norma~lly distributed in a given patient population. Further research is needed to determine optimal cutoff scores for sex offender populations. Our research addresses the use of the 16PF validity scales in forensic psychological evaluations of alleged sex offenders. Validity scales of the 16PF were significantly correlated with those of the MMPI and correctly predicted a high percentage of patients who showed minimization and exaggeration on the MMPI. Our study also supports prior findings that minimization is far more common among sex offenders than exaggeration, in comparison to nornnal populations. These data should be valuable to psychologists who conduct forensic evaluations in which patients may be motivated to distort their self-presentations.
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Linda S. Grossman Department of Psychiatry University of Illinois at Chicago 912 South Wood Street, M/C 913 Chicago, IL 60612 Received July 22, 1991 Revised October 3 1, 1991
