A validation study using 62 subjects was conducted on the Multidimensional Investigation of Neuropsychological Dissimulation (MIND), a new neuropsychological instrument used to detect exaggeration of brain-injury symptoms. This instrument has eight scoring indices that use multiple, empirically based strategies to detect poor effort. Discriminant function analysis was used to classify three groups of subjects: normals responding in a sincere manner (N=24); normals who were educated about mild to moderate head injuries and given substantial incentives to malinger without obvious detection (N=21); and clinically diagnosed, brain-injured patients with mild to moderate impairments (N=17). A univariate F test indicated significant group differences on six of the eight original predictor variables. Using these six variables, there was an overall classification rate of 68%, reflecting only a 10% false negative rate in the dissimulating group. For a two-group classification (i.e., dissimulating and mildly to moderately brain-injured subjects), an 82% overall accuracy rate was achieved. The MIND appears to have potential for identifying individuals exaggerating mild to moderate neuropsychological deficits.
Neuropsychological testing is being used with increasing frequency in medical–legal cases. The validity of neuropsychological testing is dependent upon sincere and active participation by the examinee. In cases with incentive for poor performance, there is the potential for response bias or malingering (i.e., the intentional exaggeration or feigning of impairments for secondary gain). It has been estimated that each year in the United States, 2 million head injuries occur, with most of these being minor (Kraus & McArthur, 1995). This mild head-trauma population may be most at risk for feigning neuropsychological deficits. Studies Binder, 1993, Binder & Rohling, 1995, Binder & Willis, 1991 and Trueblood & Schmidt, 1993 have shown that, given the presence of financial incentives, people with mild head injuries perform worse on some measures of effort or sincerity than those with severe head trauma.
To facilitate accurate identification of legitimate mild head-injury complaints, there has been an increase in the development of objective assessment techniques for the detection of malingering. Two main strategies characterize this research. The first involves evaluating the examinee's performance on current neuropsychological tests with what is known about typical brain functioning. Studies have shown that suspected malingerers tend to reveal different patterns of incorrect responses than actual brain-injured patients Bernard et al., 1993, Goebel, 1983, Greiffenstein et al., 1994, Heaton et al., 1978, Martin et al., 1993 and Mittenberg et al., 1993.
A second approach is the development of unidimensional measures specifically designed to detect specific deception strategies Bectar & Williams, 1995, Binder, 1993, Gudjonsson & Shackleton, 1986, Iverson & Franzen, 1994 and Wiggins & Brandt, 1988. For example, the theoretical basis for tests such as the Portland Digit Recognition Test and Rey 15-Item Test is that malingerers will tend to misjudge the level of actual difficulty of the test and perform more poorly than severely brain-injured patients.
Schretlen (1988) suggests that supplying information regarding the condition to be faked is a useful experimental strategy that is likely to increase the plausibility of faked test results. Rogers (1984) made specific recommendations for improving research design in this domain: (a) Subjects who are asked to malinger should be given an incentive for success, such as a financial award. (b) Simulation instructions (i.e., specific symptomology) must be precise and should emphasize the believability of simulated behavior. (c) Subject compliance must be studied with a debriefing interview. (d) Discriminant functions and other multivariate techniques should be used to produce standardized indicators of dissimulation.
There have been a few studies exploring the effects of coaching on neuropsychological instruments used to detect deception Frederick et al., 1994 and Martin et al., 1993. These investigators found that subjects coached in strategies to reduce detection as dissimulators performed above chance levels on forced-choice measures and obtained higher scores than subjects who did not receive information. Recent literature reviews Iverson et al., 1991, Mills & Putnam, 1995 and Niles & Sweet, 1994 of the more common instruments presently used to detect dissimulation in mild brain-injury cases have concluded that an integrated approach toward the detection of malingering is needed. To date, there are no neuropsychological instruments developed that simultaneously measure several deception strategies.
The purpose of this study was to validate a new multidimensional instrument developed specifically to measure performance patterns of suspected malingerers — the Multidimensional Investigation of Neuropsychological Dissimulation (MIND). This study examines whether sophisticated dissimulators produce a pattern of performance on the MIND inconsistent with actual head-trauma patients. To control for external and internal validity issues, this study followed methodological recommendations made by Rogers (1984) and Schretlen (1988).
