Inventory
11
The Minnesota Multiphasic Personality Inventory (MMPI) and its revision the MMPI-2 have been the subjects of well over 10,000 published studies investigating their use and properties. There are many summary studies of validity and reliability issues (Cottle, 1950;
Dahlstrom & Welsh, 1960; Dahlstrom, Welsh, & Dahlstrom, 1975; Gravitz & Gerton, 1976;
Hathaway & McKinley, 1942; Hathaway & Meehl, 1951; Holzberg & Alessi, 1949; Hom, Wanberg, & Appel, 1973; Johnson, Klingler, & Williams, 1977; Kroger & Turnbull, 1975;
McKinley & Hathaway, 1942, 1944; Mehlman & Rand, 1960; Ritter, 1974), including meta- analytic studies (Atkinson, 1986; Hiller, Rosenthal, Bomstein, Berry, & Brunell-Neulieb, 1999; Parker, Hanson, & Hunsley, 1988). Although the MMPI is one of the most frequently used and researched instruments, psychometric weaknesses have been identified such as those discussed in David Rogers' review of the original MMPI in The Seventh Mental Measurements Yearbook (1972).
The focus of the present review is on evaluating the existing literature regarding the use of the MMPI in neuropsychological assessment as well as to review literature regarding other constructs such as dissimulation, substance abuse, and psychological diagnoses when these are potentially at question in neuropsychological assessment. Interpretation research in general is also reviewed. Specifically, the MMPI has been used by researchers as an objective measure of personality for the purpose of delineating the relationship between brain function and personality. Four general research approaches have been used in this endeavor. In the first approach, a localizationalist approach is used in an attempt to relate differences in personality (as demonstrated on the MMPI) to specific areas of brain dysfunction. With the MMPI-2, this approach has taken the form of trying to identify MMPI profiles associated with specific disorders, such as cerebrovascular accident (CVA) patients or head injury patients. The second research approach attempts to differentiate neurologically impaired subjects from some other group of subjects (e.g., schizophrenics) by identifying the differences in their response patterns. The third research approach uses deficits on neuropsychological tests as a means of defining group inclusion. Those subjects whose performance falls at the brain-damaged level are compared for personality differ- ences on the MMPI. The fourth design involves the use of correction factors for the over-
171
lap of neurological symptoms with psychiatric symptoms. Yet another use of the MMPI, primarily the MMPI-2, is to identify those subjects whose neuropsychological test perfor- mance is influenced by psychological factors, especially by response bias characteristics.
The MMPI lends itself to research of this type on theoretical grounds and on the basis of the nature of its test items and its scale composition. For example, as Lezak and Glaudin (1969) noted, among the 51 items of the 357 scored items on a short form of the MMPI (omitting scale Si and all items normally not scored) that are referable to symptoms of physical disease, 26 relate to central nervous system diseases and 8 describe problems associated with being ill. Many of the "neurological symptom" items have double and triple MMPI scale loadings.
With the advent of the MMPI-2, one might expect that use of the MMPI would de- cline. While a decline may certainly be present, the MMPI is still marketed by its publisher, and is still in current use. There are several reasons for this dual usage. First, the MMPI has been available and in near universal use for nearly 40 years; old habits are the hardest to break. Second, the amount of research available to inform the interpretation of the MMPI is quantitatively superior to that of the MMPI-2, although this will certainly change. Third, initial research indicates that although there are substantial similarities between the MMPI and the MMPI-2, there are also substantial differences, such as in the concordance of 2-point codes. Some clinicians may feel more confident using the earlier version. There- fore, this chapter includes discussion of both versions of the MMPI.
MMPI
Reliability
Although there has been research on the development of new scales to assess neuro- psychological impairment by recombining items, there have been no investigations regard- ing the forms of reliability of these new scales. However, because some of the research has concerned the use of the clinical scales of the MMPI, the reliability investigations for the clinical scales are relevant here. It must be noted that none of these studies involved individuals with organic brain impairment. Dahlstrom et al. (1975) collected data from different studies into a data base related to the reliability of the MMPI scales. Many of the reliability studies were conducted on college students. In a study using 288 male and 33 female college students, the test-retest reliability coefficients with a I-day interval ranged from .97 for the F Scale for males to .71 for Scale 6 for females. In a sample of 42 college males and 55 college females, and with test-retest intervals of 1 to 2 weeks, the reliability coefficients ranged from .49 for Scale 6 in males to .92 for both the K Scale and Scale 7 in the females. Internal-consistency reliability coefficients ranged from - .05 for Scale I in 97 college students to .90 for Scale 1 in 220 VA patients. In certain code types (Spike 4, 2-4/4-2, 2-717-2, and 6-8/8-6), there is remarkable stability of both validity scales and clinical scales across a 40-year period (Greene, 1990).
Hunsley, Hanson, and Parker (1988) reviewed the reliability research and concluded that individual scales have acceptable stability and internal consistency. The Spanish trans- lation of the MMPI has parallel temporal reliability (Traub & Bohn, 1985). The high-point, 2-point, and 3-point codes of the MMPI have low temporal consistency, but it is unclear as
to whether this is related to instability of the instrument or behavioral change in the subjects (Graham, Smith, & Schwartz, 1986).
Validity Localizationalist Paradigm
As noted previously, researchers have speculated on the relationship between person- ality changes and the location of the cerebral insult. Anderson and Hanvik (1950), for example, attempted to characterize the differences between patients with parietal lobe damage and those with frontal lobe damage, but there were no tests for statistical signifi- cance of the differences between groups. In addition, the groups were not pure, as the parietal group contained subjects with damage to the temporal and occipital lobes.
Friedman (1950) developed a 132-item parietal-frontal (PF) scale with reasonable success (Dahlstrom & Welsh, 1960). Williams (1952) constructed a similar scale, the Caudality (Ca) scale, in which 40% of Friedman's scale was reproduced. Williams's 36- item scale was reported to significantly differentiate patients with parietal and temporal lesions, as a group, from those with frontal lesions (Dahlstrom & Welsh, 1960; Meier, 1969). Reitan (1976), however, reported that later research did not support these earlier findings.
Black (1975) and Templer and Connolly (1976) attempted to separate the associated personality variables within a laterally dichotomized (left- vs. right-hemisphere) brain- damaged population. In Black's study, for example, differential effects were found in the two groups. On the F, K, D, Pa, Sc, and Si scales, the left-hemisphere-damaged subjects scored significantly higher (p
<
.05) than did the right-hemisphere-damaged subjects and had greater cognitive and neurosensory deficits.Using the lesion localization paradigm, Vogel (1962) attempted a global study of effects on the MMPI. Vogel (1962) investigated whether left-hemisphere-Iesioned subjects would show a more pathological profile than right-hemisphere-Iesioned subjects, and whether subjects with parietal and temporal lobe damage would show a more pathological profile than those with frontal lobe damage. The overall index of MMPI pathology was operationalized as the number of scales greater than 70. The study results did not support the original hypotheses. Dikmen and Reitan (1974b) failed to demonstrate personality changes as a result of medically conclusive locations of brain damage along rostrocaudal as well as lateral dimensions. These investigators concluded that the MMPI was a poor mea- sure of personality changes when groups were derived according to the location of brain damage, but it might also be that reliable changes in personality secondary to localizable injury are minor compared to individual variation in psychological response. In a study using subjects with mixed organic diagnoses (Flick & Edwards, 1971) and in a study of patients with temporal lobe epilepsy (Meier & French, 1965), similar negative results were reported. Consistent with the foregoing discussion, Lezak (1995) described lateralization research results as being equivocal.
In summary, little reproducible evidence has been generated by the localizationalist approach to the study of brain-personality relationships. The problem may be related to the different effects of lesions even within the same broad area of the brain because of differences in their etiology, the time since onset, the medical treatments, their pressure
effects, and their exact location (Luria, 1966; Reitan, 1966). Finally, observed personality differences may relate more to differences in the behavioral deficits suffered by individuals than to the area of the damage.
Differential Performance Paradigm
The second approach taken to delineate the personality patterns characteristic of brain damage is to compare the performance of brain-injured subjects with that of nonneurologi- cally impaired subjects to identify differentiating scales or items on the MMPI. Studies have included investigations of the MMPI scores of patients diagnosed with multiple sclerosis (Dahlstrom & Welsh, 1960; Gilberstadt & Farkas, 1961; Schwartz & Brown, 1973), epilepsy (Klove & Doehring, 1962; Kristianson, 1974; Matthews, Dikmen, &
Harley, 1977; Meier, 1969; Small, Milstein, & Stevens, 1962; Stein, 1972), Huntington's disease (Boll, Heaton, & Reitan, 1974; Norton, 1975), and Guillain-Barre syndrome (Sziraki, 1978). Similarly, traumatically brain-injured subjects have been compared with normals (Hovey, 1964), neurotics (Reitan, 1955a), schizophrenics (Ayers, Templer, & Ruff, 1975; Holland, Lowenfeld, & Wadsworth, 1975a; Markowitz, 1973; Neuringer, Dom- browski, & Goldstein, 1975; Russell, 1977; Watson, 1971), and psychiatric patients in general (Shaw & Matthews, 1965).
The MMPI has been found to differentiate between organically impaired and psychi- atric or normal subjects (Matthews et aI., 1966; Reitan, 1955a; Watson & Thomas, 1968), but no profile unique to one group has emerged. For example, in the study by Reitan (1955a), a heterogeneous brain-damaged group scored higher on the F, Pa, Pt, Sc, and Ma scales of the MMPI than did the control group. The experimental subjects varied according to the type, extent, and location of the brain lesion and were matched for sex, age, and education with members of a control group that contained normal and neurotic subjects with no known brain damage. The experimental group yielded a wide range of personality profiles.
In contrast to the Reitan study, Watson and Thomas (1968) compared neurological patients with schizophrenic patients on the 10 MMPI scales and found significant differ- ences on the Hs, D, Mf, Pt, Sc, and Si. Four decision rules were developed (a strategy to be discussed in detail later) that yielded a 69% correct classification. Three validation studies yielded classification rates of 71 %, 79%, and 45%. Norton and Romano (1977) conducted a cross-validation study of the Watson-Thomas rules on a sample of 14 neurological patients, 14 alcoholic patients, 14 married schizophrenic patients, 14 unmarried schizophrenic pa- tients, and 14 patients with mixed psychiatric diagnosis who lacked neurological symp- toms. These authors reported generally good levels of accuracy of classification for all except the unmarried schizophrenic patients. However, the accuracy of their classification rates may have been inflated by their use of "pure" cases and by the use of equal fre- quencies of subjects in all groups. The most consistent finding in these studies, aside from being unable to generate a common patient profile, was that the Sc scale can differentiate psychotic patients from organically impaired patients (e.g., Russell, 1977).
The second approach to diagnosis with the MMPI has been to establish organicity scales that can discriminate between experimental and control groups (Hovey, 1964; Shaw
& Matthews, 1965; Watson, 1971; Watson & Plemel, 1978). The results of these studies have been highly variable, because of the use of populations that varied widely in severity,
chronicity, type of injury, age, education, and duration of hospitalization (Ayers et al., 1975;
Holland et aI., 1975a; Neuringer et al., 1975; Pantano & Schwartz, 1978; Ruff, Ayers, &
Templer, 1977; Russell, 1977; Sand, 1973; Siskind, 1976; Upper & Seeman, 1966; Zimmer- man, 1965). Few studies have attempted to compare any combination of these scales on a single population to eliminate much of the interpretive problem in the current literature.
In the Hovey (1964) study the five items were chosen from the MMPI that appeared to be most able to discriminate brain-injured patients and controls. Items 10, 51,192, and 274 are marked false, and Item 159 is marked true. The cutoff score for organicity is 4. Hovey recommended that, to minimize the possibility of false-positive errors, this scale be used only when the K-scale raw score is 8 or above. Using these five items, Hovey correctly classified 50% of the brain-damaged subjects; there was a 9% to 18% misclassification rate of the normal subjects. Upper and Seeman (1966) cross-validated Hovey's scale using a non-brain-damaged schizophrenic control group and found similar differences between groups. Overall, however, the Hovey five-item scale has met with only limited success.
This scale was found to be ineffective in discriminating patients with organic impairment from groups of organically intact patients with functional disorders (Dodge & Kolstoe, 1971; Maier & Abidin, 1967; Schwartz & Brown, 1973), schizophrenic patients (Watson, 1971), and normal control subjects (Weingold, Dawson, & Kael, 1965). A classification of chronic alcoholic patients by the Hovey scale was not found to bear any systematic relation- ship to cognitive indices of organic impairment (Chaney, Erickson, & O'Leary, 1977).
Jortner (1965) also reported a failure to replicate Hovey's results.
Watson (1971) abandoned his attempt to develop a profile indicative of neuropsycho- logical impairment in favor of developing a new MMPI scale, the Schizophrenia-Organicity (Sc-O) scale, for differentiating brain-damaged patients from schizophrenic patients.
Eighty items were initially identified and combined to form the scale. Two other scales were derived from the original 80 items by first weighting all of the items according to their power of discrimination, and then by weighting only the 30 most powerful items. Using these scales, Watson reported 85% accuracy; on cross-validation with a similar patient popUlation, the scale yielded 76% accuracy. However, there were later failures in attempts to cross-validate the findings (Halperin, Neuringer, Davis, and Goldstein, 1977; Holland et aI., 1975a).
Watson (1973) noted that the Sc-O Scale does not separate non schizophrenic func- tional groups from organically impaired groups. Therefore, he developed the Psychiatric- Organic (P-O) Scale. This scale consists of 56 items that were found to differentiate 40 brain-damaged subjects from a group of 60 psychiatric patients (all subjects were male veterans). The group of functionally disordered patients consisted mostly of alcoholics (35). The P-O scale correlates positively with age (R = .30). The internal consistency of the scale, as reported by Watson and Plemel (1978), was .90 for the organics, and only .68 for the control. Additional research is needed before one can use this scale with additional populations.
Shaw and Matthews (1965) also addressed the problem of differentiating between organic and psychiatric deficits by developing a neurological impairment scale-with two important differences. Here, the subject-sampling procedure included "pseudoneurologi- cal" patients who were diagnosed as being psychiatric patients but who also manifested
"soft" neurological symptoms. This study also differed in the procedure it used to identify the items to be included in the scale: 17 items, 5 of which are marked true (38, 47,108,238,
and 253) and 12 of which are marked false (3, 8, 68, 171, 173, 175, 188, 190, 230, 237, 238, and 243), were chosen from only those scales that, as a whole, differentiated between the two groups (Hy, Hs, and Pt). Items on other scales that mayor may not have differentiated between the groups were excluded from analysis. A cutoff score of 7 was established for the scale.
Originally, an accuracy of78% was reported. A cross-validation sample yielded 73%
correct classifications, with misclassifications 33% of the time in the psychiatric group and 22% of the time in the neurological group. Again, the scale failed to meet the criterion normally expected of a clinical diagnostic device.
The final strategy within this research design entails the use of the MMPI in the development of decision rules for diagnosing organicity. In this approach, an algorithm or decision tree with a hierarchy of rules is used to differentiate the diagnostic categories.
Major systems of this type have been proposed by Watson and Thomas (1968) and Russell (1975b, 1977). Limited success has been reported for these approaches. For example, in a study of 20 brain-damaged, 21 schizophrenic, and 24 clinically depressed subjects, Trifiletti (1982) found that Russell's MMPI key correctly identified 85% of the brain-damaged subjects and 0% of the schizophrenics, and only 33% of the depressed subjects; the overall hit rate was 68%. Overall, it must be concluded that additional cross-validation is needed for decision-tree-algorithm approach to the differential diagnosis of organicity.
Golden, Sweet, and Osmon (1979) compared each of the above approaches in their study of a single popUlation consisting of 30 schizophrenic, 30 brain-injured, and 30 hospitalized normal patients. Their results indicated that the most effective diagnostic device was the use of the Sc scale alone or in conjunction with the remaining clinical scales and the F scale. The result of this study does not support the existence of a unique organic profile. The study does support the effectiveness of the Sc and Pa scales in the diagnosis of brain damage. These results were identical to those reported by Russell (1977). These findings suggest that the greater the degree of psychosis present, the less likely is the presence of an organic brain syndrome. However, as noted by Golden et al. (1979), even this limited conclusion is questionable. The Golden et al. (1979) study did not include individ- uals with brain damage who were also psychotic. It is likely that such a group would show high elevations on the Sc, Pa, and other MMPI scales equal to those shown by the schizo- phrenic group without brain damage. Thus, when a diagnosis of organic brain syndrome with psychosis is considered, even the presence of psychosis cannot rule out the presence of brain damage.
Although the second research design (differentiating groups by their performance on the MMPI) shows that personality differences do exist between brain-damaged and non- brain-damaged psychopathological groups, it has been unable to produce clinically useful diagnostic devices, with large differences found among brain-injured subjects (Reitan, 1955a).
The difficulty of cross-validating research in this area may also be attributable to the fact that those general pattern tendencies that characterize the responses of the neurologi- cally impaired subject may only be an artifact of the test items and the scale composition of the MMPI. For example, a confounding factor in research of this type is that many of the
"neurological symptom" items appear on the Sc scale, and many have double and triple scale loadings, particularly on scales Hs, D, and Hy. As a result, nonpsychiatric patients with central nervous system disease tend to have an elevated "neurotic triad" (Hs, D, and Hy) (Dikmen & Reitan, 1974b) and higher-than-average Sc scores. Pt is also among the
scales most likely to be elevated in an organic population (Mack, 1979). Schwartz (1969) examined both the 1-3-9 and the 2-9 profiles in a sample of 50,000 consecutive medical outpatients. Using the 1-3-9 rules resulted in a sample of 24 subjects. Using the 2-9 rules resulted in a sample of 23 subjects. There were no differences in the independently detennined degree of organic impairment between these subjects and control subjects with 1-3/3-1 profiles who were matched for age, sex, and date of clinic appointment. In addi- tion, only one of the 1-3-9 subjects and five of the 2-9 subjects had been diagnosed as organically impaired. These results seriously question the accuracy of the rules.
The 2-9 and 1-3-9 scale elevations once thought to represent organic patterns have not been validated (Russell, 1977). However, Casey and Fennell (1981) reported elevations on Scales 2, 8, and 1 that characterized the MMPI profiles of traumatically injured patients:
Heaton et al. (1978) also observed that head-injured patients tended to have elevated scores on Scales 2 and 8. In general, elevated MMPI profiles tend to be common among brain- damaged populations, a finding reflecting the relatively frequent incidence of emotional disturbance in these patients (Filskov & Leli, 1981). The tendency of Sc to be one of the highest scales has been noted for epileptic patients (Klove & Doehring, 1962; Meier, 1969).
High scores on the neurotic triad have characterized the MMPI profiles of patients with multiple sclerosis (Dahlstrom & Welsh, 1960). Huntington's disease patients, too, have abnormally high score profiles, but these profiles are indistinguishable from the profile pattern of heterogeneous groups of brain-damaged patients (Boll et aI., 1974; Norton, 1975).
Thus, for brain-damaged patients, acknowledgment of specific symptoms accounts for some of the elevation of specific scales. Premorbid personality tendencies and the patient's reactions to his or her disabilities also contribute to the MMPI profile. The combination of the symptom description, the anxiety and distress occasioned by central nervous system defects, and the need for adaptive psychological measures probably accounts for the frequency with which brain-damaged patients produce neurotic profiles.
NeuropsychoLogicaL Functioning as a Means of Defining Group Inclusion
The third paradigm was developed in response to the failure of the first two ap- proaches. This paradigm assumes that behavioral deficits specifically related to a brain lesion can be used to create more exact definitions of brain-injured groups, and therefore to make more homogeneous samples possible. As a result, a group with similar behavioral deficits can be identified. In such groupings, one need not presuppose an all-encompassing personality profile of brain damage.
In an early study by Doehring and Reitan (1960), behavioral deficits were used to define three groups of diagnoses: brain-damaged aphasic dysfunction, brain-damaged nonaphasic dysfunction, and intact neurosis, but no significant differences were found for the MMPI scales.
It was later suggested by Dikmen and Reitan (1974a) that the failure of the Doehring and Reitan (1960) study to find personality differences between the three groups was probably due to the heterogeneity of the personality deficits in the neurotic group, which masked any intergroup differences that might have existed and to the method of data analysis. When the neurotic group was eliminated and the data were reanalyzed using t
ratios, significant differences on the Pd and Sc scales were found between the two brain- damaged groups.
In a similar study, Dikmen and Reitan (1974a) successfully demonstrated personality