Serial Malingering on Verbal and Nonverbal Fluency and Memory Measures: An Analog Investigation

Archives of Clinical Neuropsychology, Vol. 14, No. 4, pp. 401–410, 1999 Copyright © 1999 National Academy of Neuropsychology Printed in the USA. All rights reserved 0887-6177/99 $–see front matter PII S0887-6177(98)00039-0 Serial Malingering on Verbal and Nonverbal Fluency and Memory Measures: An Analog Investigation George J. Demakis Elmhurst College Analysis of response consistency on neuropsychological test performance, both within and across testing sessions, can be an important method of detecting malingering. Little systematic research, however, has examined how suspected malingerers perform across repeat evaluations, a common forensic occurrence. To address this issue, we examined performance across a 3-week interval in an analogue malingering design on the California Verbal Learning Test (CVLT), the Rey Complex Figure, the Controlled Oral Word Association Test, and the Ruff Figural Fluency Test. Malingering simulators (n 5 21) performed more poorly on all measures than the controls (n 5 21) and demonstrated practice effects on the nonverbal, but not the verbal, tests. Controls demonstrated practice effects on all measures across time. Contrary to hypotheses, malingering simulators demonstrated high and similar levels of between and within time consistency as controls when assessed via a series of correlations. Despite this consistency, when qualitative performance patterns were assessed on the CVLT, simulators were less likely to consistently recall the same word across successive learning trials. The following issues are discussed: (a) the differential pattern of practice effects on verbal and nonverbal tasks, (b) qualitative and quantitative differences in assessment of consistency, and (c) how future research should study consistency/inconsistency. © 1999 National Academy of Neuropsychology. Published by Elsevier Science Ltd Several methods of detecting malingering have been devised, including the use of specific malingering tests (e.g., forced choice tests), analysis of performance level and pattern on commonly used neuropsychological tests, and examination of nonsensical test patterns. While considerable research has investigated these approaches (for reviews, see Nies & Sweet, 1994 and Rogers, Harrell, & Liff, 1993), less systematic research has examined performance consistency, whether between or within test sessions, in suspected malingerers. This gap is surprising, given the frequency with which suspected malingerers are evaluated in the forensic context and suggestions that malingerers may Portions of this paper were presented at the 105th annual meeting of the American Psychological Association in Chicago, August, 1997. This research was supported by a faculty development grant from Elmhurst College. The author thanks Jerry J. Sweet for helpful comments on an earlier draft of this manuscript and Carla Cihlar for assistance running participants. Address correspondence to George J. Demakis, Elmhurst College, Department of Psychology, 190 Prospect Avenue, Elmhurst, IL 60126; E-mail: 401 402 G. J. Demakis present with clinical and/or neuropsychological test performance inconsistencies (Cullum, Heaton, & Grant, 1991; Rawling, 1993; Reitan & Wolfson, 1998; Rogers, 1984; Zielinski, 1994). These inconsistencies can be an important way of detecting malingering and can manifest in several ways, with poor or unexplainable relationships between the following: injury severity and cognitive function, premorbid abilities and abilities measured postinjury, tests tapping the same construct (e.g., verbal memory), and repeat administrations of the same test or test items (Rawling, 1993). Presumably, these inconsistencies become apparent during the neuropsychological evaluation, as malingerers do not consistently and fully exert maximal effort. Overall, despite the relative paucity of research in this area, many clinicians appear to agree with Cullum et al. (1991) that assessment of response consistency is a powerful means of detecting malingering. A common approach used by investigators to demonstrate the importance of response consistency is case study analysis of neuropsychological performance. For instance, Cullum et al. (1991) presented three case studies of serial performance by suspected malingerers in the forensic setting. Compared to controls or neurologically stable patients, they demonstrated highly variable neuropsychological performance over two or more evaluations that did not reflect a consistent pattern of improvement or deterioration. For example, Patient 2 demonstrated a marked deterioration in performance on Trails B (1129 seconds), which, according to the authors, was suspicious of malingering. In a quite different, but relevant, case study by Sweet and Kuhlman (1993), consistency across four repeat neuropsychological examinations was viewed as critical to establishing the veracity of a litigant’s complaints. Putnam, Adams, and Schneider (1992) also demonstrated fairly consistent performance, with some expected practice effects, in a patient who underwent forensic neuropsychological evaluation on two successive days. Although not concerned with malingering per se, the similar performance on both days could be used to bolster the conclusion that this patient exerted maximal effort on testing and responded honestly. In all, these case studies illustrate how clinicians tend to assess and use response consistency (or inconsistency) to make clinically meaningful decisions. In addition to these case studies, a few systematic efforts have assessed response consistency and test-retest performance. Paul, Franzen, Cohen, and Fremouw (1992) examined serial malingering on 2-week retesting on Rey’s Dot Counting and Memorization of 16 Items tests. Relative to controls, malingering simulators performed more consistently on four of the seven measures assessed on these tests. Lezak (1995), however, notes that the relatively low correlations for the controls likely reflected ceiling effects, as most performed with near-perfect accuracy statistically exaggerating the effect of slight changes in performance between trials. In a more clinically relevant study, Trueblood (1994) examined neuropsychological performances of a small group of documented malingerers and head-injury controls. Though the malingerers scored significantly more poorly than controls on several memory and intelligence measures, they responded as consistently as controls on several verbal memory tasks, including the California Verbal Learning Test (CVLT) and Logical Memory and Paired Associates subtests of the Wechsler Memory Scales. Consistency was operationalized as the difference between each person’s highest- and lowest-ranked memory score; each score was ranked based on its standing with the combined group of control and malingering subjects. Malingerers also performed as consistently across the five learning trials of the CVLT. Two studies by Reitan and Wolfson (1996, 1997) used archi (...truncated)