- Email: [email protected]
Comparison of the full and shortened form of the PDRT in malingering detection
Abstractsfrom the 19th Annual Meeting
747
sumed that patients will be equally likely to fail different symptom validity tests (SVT), whether the test involves digit recognition or some other procedure, such as word memory. The layman typically associates impaired cognitive function with deficits in verbal memory. Therefore, an SVT based on verbal memory might be more sensitive to incomplete effort than a digit recognition procedure. In this study, 150 patients referred for disability or personal injury related assessments were administered three SVTs, one based on digit recognition (Computerized Assessment of Response Bias, CARB), one on visual stimuli (Test of Memory Malingering, TOMM), and one employing a verbal memory task (Word Memory Test, WMT). More people failed the WMT than CARB and the lowest failure rate was on the TOMM, even though these tests are objectively of equal difficulty and are equally insensitive to memory impairment. It will be argued that the perceived relevance of the test material to the person's claimed cognitive impairment in daily life is an important factor to consider in selecting SVTs.
Schatz, P., Moeiter, S., & Fragnito, M. Computer-Based Assessment of Malingering: Response Requirement Effects. Four computer-based tests were administered to 75 normal subjects who were provided with detailed instructions to do their best or fake bad. The tasks were: (a) a revised version of the Rey 15-item test; (b) computerized version of the Ray Dot-Counting test; (c) the University of Pennsylvania Trucks test, and (d) a custom Fill-in-the-blank "Phrases" test (i.e., _ _ birthday to you.). Experimental tasks were administered in this order to all subjects, who participated in both experimental conditions which were counterbalanced. Millisecond accurate reaction time data was recorded (Power Laboratory, © Chute & Westall, 1996) for all subject responses for all aspects of the experiments, including actual responses to stimuli as well as responses to instruction screens. Subjects who were "faking bad" achieved significantly lower percent correct on all experimental tasks. On tasks where obvious "bad" responses were not readily apparent (15-item, Phrases), subjects faking bad required significantly more time to provide responses. In contrast, where the alternate response was a "mouse-click" away (Trucks) or obviously a number (Dot counting), groups did not differ on response time, and those faking bad actually performed these tasks in less total time. Analysis of response time to identical instruction screens revealed a learning curve for both groups. This would be expected for those subjects who were doing their best. However, for subjects who were faking bad, such a learning curve in the context of an inability to count dots, recall simple items, or complete over-learned phrases is clearly "out of register." The response requirements, gender effects, and reaction time components of these tests are sufficiently complex that profiling of individuals exhibiting inconsistent response sets or questionable motivation on evaluations may be possible.
Gunstad, J., & Suhr, J. Comparison of the Full and Shortened Form of the PDRT in Malingering Detection. Though a short form of the popular malingering test, the Portland Digit Recognition Test (PDRT) has been described, it has never been validated. The present study sought to determine the ability of the short form to discriminate among malingerers given different levels of information and coaching. A total of 80 undergraduates completed the P D R T as part of a larger battery of neuropsychological tests. Participants were randomly assigned to one of four conditions, Normal Effort (Effort; n = 20), Na'~ve Malingerers (NaYve; n = 20), Malingerers with Information (Informed; n = 20), and Malinger-
748
Abstracts from the 19th Annual Meeting
ers with Information and Warning (Warned; n = 20). Individuals in the Effort condition were asked to perform their best. Those in the Naive condition were asked to portray the deficits associated with that accident. Informed individuals also received non-specific information about head injury sequelae. Participants in the Warned condition received the same information plus a general warning about malingering detection during the evaluation. A N O V A revealed group differences at each level of the P D R T (5-, 15-, and 30-second delay). The Effort group performed better than Warned, and both Na'fve and Informed malingerers performed worse than Warned on the 15-second delay, the 30-second delay, and the full PDRT. Effort and Warned groups were equivalent on the 5-second delay, though Effort performed reliably better than the other malingering groups. A comparison of the abbreviated forms with the full length P D R T shows the shortened versions are superior to the full scale at detecting simulated malingerers in all three groups (chi-squares ranging from 4.51 to 9.25, all significant at p < .05). The liberal abbreviated version (6 of 9 hard items) was able to identify 60% of the Naive malingerers, 75% of the Informed malingerers, and 20% of the Warned malingerers with 100% specificity. The conservative form (7 of 9 hard items) was able to detect 80% of both the Naive and Informed malingerers and 35% of the Warned malingerers, with 100% specificity. The full scale cut-offs identified 35% of the Naive malingerers, 20% of the Informed malingerers, and 0% of the Warned malingerers, with 100% specificity. Analyses also showed that the Warned individuals were better able to avoid detection than the Informed individuals using either the conservative form or the full P D R T (chi-squares ranging from 4.23 to 13.5, all significant at p < .05). The results of this study support the hypothesis that the P D R T is vulnerable to even minimal amounts of coaching. Also, use of the full-length P D R T is contraindicated, as an abbreviated form better identified malingerers from each condition. These findings suggest development of more sophisticated forms of malingering detection should continue, whether by creating new techniques or through analysis of performance on existing tests.
Suhr, J. A., & Cartwright, M. The Serial Position Effect and Malingering: The Effects of Coaching. Malingerers do less well on standardized neuropsychological measures, often performing in a way that is similar to or even below that of persons with brain injury. However, cut-off scores on standardized tests do not always differentiate between actual brain injury and malingering. Recently, malingering researchers have been examining patterns of performance on neuropsychological tests that may be more sensitive and specific to malingering. One possible pattern is the serial position effect. Normals, head injured patients, and psychiatric patients with cognitive complaints tend to show both a primacy and recency effect on list learning tasks, while both patient and undergraduate malingerers show suppression of the primacy effect. Thus, there is some evidence that an abnormal pattern of serial position will be useful in detecting malingering. However, to be effective in malingering detection, this pattern must not be vulnerable to the effects of coaching. In the present study, we explored whether this pattern is vulnerable to coaching. Subjects were 34 undergraduates asked to perform with their best effort, 38 undergraduates asked to simulate head injury, 33 undergraduates asked to simulate head injury but also given information about head injury and a general warning about the possibility of malingering detection, and 17 patients with head injury (mean age = 25.41 years, mean years of education = 12.94, mean days posttraumatic amnesia = 10.93, mean days hospitalization = 44.2). Undergraduates participated in a 2-hour neuropsychological evaluation which included the Rey Auditory Verbal Learning Test (AVLT). All patients received the A V L T as part of a larger clinical evaluation. To examine the
747
sumed that patients will be equally likely to fail different symptom validity tests (SVT), whether the test involves digit recognition or some other procedure, such as word memory. The layman typically associates impaired cognitive function with deficits in verbal memory. Therefore, an SVT based on verbal memory might be more sensitive to incomplete effort than a digit recognition procedure. In this study, 150 patients referred for disability or personal injury related assessments were administered three SVTs, one based on digit recognition (Computerized Assessment of Response Bias, CARB), one on visual stimuli (Test of Memory Malingering, TOMM), and one employing a verbal memory task (Word Memory Test, WMT). More people failed the WMT than CARB and the lowest failure rate was on the TOMM, even though these tests are objectively of equal difficulty and are equally insensitive to memory impairment. It will be argued that the perceived relevance of the test material to the person's claimed cognitive impairment in daily life is an important factor to consider in selecting SVTs.
Schatz, P., Moeiter, S., & Fragnito, M. Computer-Based Assessment of Malingering: Response Requirement Effects. Four computer-based tests were administered to 75 normal subjects who were provided with detailed instructions to do their best or fake bad. The tasks were: (a) a revised version of the Rey 15-item test; (b) computerized version of the Ray Dot-Counting test; (c) the University of Pennsylvania Trucks test, and (d) a custom Fill-in-the-blank "Phrases" test (i.e., _ _ birthday to you.). Experimental tasks were administered in this order to all subjects, who participated in both experimental conditions which were counterbalanced. Millisecond accurate reaction time data was recorded (Power Laboratory, © Chute & Westall, 1996) for all subject responses for all aspects of the experiments, including actual responses to stimuli as well as responses to instruction screens. Subjects who were "faking bad" achieved significantly lower percent correct on all experimental tasks. On tasks where obvious "bad" responses were not readily apparent (15-item, Phrases), subjects faking bad required significantly more time to provide responses. In contrast, where the alternate response was a "mouse-click" away (Trucks) or obviously a number (Dot counting), groups did not differ on response time, and those faking bad actually performed these tasks in less total time. Analysis of response time to identical instruction screens revealed a learning curve for both groups. This would be expected for those subjects who were doing their best. However, for subjects who were faking bad, such a learning curve in the context of an inability to count dots, recall simple items, or complete over-learned phrases is clearly "out of register." The response requirements, gender effects, and reaction time components of these tests are sufficiently complex that profiling of individuals exhibiting inconsistent response sets or questionable motivation on evaluations may be possible.
Gunstad, J., & Suhr, J. Comparison of the Full and Shortened Form of the PDRT in Malingering Detection. Though a short form of the popular malingering test, the Portland Digit Recognition Test (PDRT) has been described, it has never been validated. The present study sought to determine the ability of the short form to discriminate among malingerers given different levels of information and coaching. A total of 80 undergraduates completed the P D R T as part of a larger battery of neuropsychological tests. Participants were randomly assigned to one of four conditions, Normal Effort (Effort; n = 20), Na'~ve Malingerers (NaYve; n = 20), Malingerers with Information (Informed; n = 20), and Malinger-
748
Abstracts from the 19th Annual Meeting
ers with Information and Warning (Warned; n = 20). Individuals in the Effort condition were asked to perform their best. Those in the Naive condition were asked to portray the deficits associated with that accident. Informed individuals also received non-specific information about head injury sequelae. Participants in the Warned condition received the same information plus a general warning about malingering detection during the evaluation. A N O V A revealed group differences at each level of the P D R T (5-, 15-, and 30-second delay). The Effort group performed better than Warned, and both Na'fve and Informed malingerers performed worse than Warned on the 15-second delay, the 30-second delay, and the full PDRT. Effort and Warned groups were equivalent on the 5-second delay, though Effort performed reliably better than the other malingering groups. A comparison of the abbreviated forms with the full length P D R T shows the shortened versions are superior to the full scale at detecting simulated malingerers in all three groups (chi-squares ranging from 4.51 to 9.25, all significant at p < .05). The liberal abbreviated version (6 of 9 hard items) was able to identify 60% of the Naive malingerers, 75% of the Informed malingerers, and 20% of the Warned malingerers with 100% specificity. The conservative form (7 of 9 hard items) was able to detect 80% of both the Naive and Informed malingerers and 35% of the Warned malingerers, with 100% specificity. The full scale cut-offs identified 35% of the Naive malingerers, 20% of the Informed malingerers, and 0% of the Warned malingerers, with 100% specificity. Analyses also showed that the Warned individuals were better able to avoid detection than the Informed individuals using either the conservative form or the full P D R T (chi-squares ranging from 4.23 to 13.5, all significant at p < .05). The results of this study support the hypothesis that the P D R T is vulnerable to even minimal amounts of coaching. Also, use of the full-length P D R T is contraindicated, as an abbreviated form better identified malingerers from each condition. These findings suggest development of more sophisticated forms of malingering detection should continue, whether by creating new techniques or through analysis of performance on existing tests.
Suhr, J. A., & Cartwright, M. The Serial Position Effect and Malingering: The Effects of Coaching. Malingerers do less well on standardized neuropsychological measures, often performing in a way that is similar to or even below that of persons with brain injury. However, cut-off scores on standardized tests do not always differentiate between actual brain injury and malingering. Recently, malingering researchers have been examining patterns of performance on neuropsychological tests that may be more sensitive and specific to malingering. One possible pattern is the serial position effect. Normals, head injured patients, and psychiatric patients with cognitive complaints tend to show both a primacy and recency effect on list learning tasks, while both patient and undergraduate malingerers show suppression of the primacy effect. Thus, there is some evidence that an abnormal pattern of serial position will be useful in detecting malingering. However, to be effective in malingering detection, this pattern must not be vulnerable to the effects of coaching. In the present study, we explored whether this pattern is vulnerable to coaching. Subjects were 34 undergraduates asked to perform with their best effort, 38 undergraduates asked to simulate head injury, 33 undergraduates asked to simulate head injury but also given information about head injury and a general warning about the possibility of malingering detection, and 17 patients with head injury (mean age = 25.41 years, mean years of education = 12.94, mean days posttraumatic amnesia = 10.93, mean days hospitalization = 44.2). Undergraduates participated in a 2-hour neuropsychological evaluation which included the Rey Auditory Verbal Learning Test (AVLT). All patients received the A V L T as part of a larger clinical evaluation. To examine the