The Relative utility of implicit memory tasks and a forced-choice memory test for the detection of simulated brain injury deficits




Fisher, Kimberly Gail

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Clinical neuropsychologists are often called upon to make decisions on the genuineness of cognitive deficits following a head injury. This is a difficult task, particularly when deficits are subtle, as there are few reliable tools to aid the clinician in his or her decision making process. In the present study, normal participants instructed to feign brain injury (M) , traumatically brain-injured individuals (BI) , and normal controls (C), completed a series of computer-administered implicit memory (IM) tasks. Results were compared to those for the Victoria Symptom Validity Test (VSVT; Slick, Hopp, Strauss, & Pinch, 1994; Slick, Hopp, Strauss, & Thompson, 1997), a commercially available forced-choice recognition task. All IM tasks included items which had been previously presented once, twice or four times, as well as foils (items not previously presented). Previous exposure to test items was expected to be associated with increased accuracy (Hits) and decreased Response Latency. Participants in the BI and C groups were expected to perform equally well and better than the M group participants with respect to Hits. Response Latency on incorrect items (Misses) was also expected to discriminate M participants from BI and C participants because the conscious decision to provide an incorrect response was expected to increase decision making time. Results with respect to overall Hits were confirmed (M=127.87, M=129.72, and M=107.10 for the BI, C, and M groups, respectively) . Increased accuracy with repetition of items in the priming phase was not confirmed, likely because both BI and C participants performed close to ceiling levels. Discriminant function analysis based on total Hit rates, resulted in correct classification of 85 percent (46 out of 54) of the participants. This was comparable to the results for Hard items combined on the VSVT. Response Latency measures did not effectively discriminate among groups, while results did indicate a main effect of Presentation Level (priming) on Response Latency with participants, independent of Group Membership, tending to respond most quickly (Hits only) to items presented 4 times during the priming phase and least quickly to items presented only once. Overall, results suggest that further investigation of IM tasks for the detection of conscious malingering is warranted as these tasks appear to tap the dimensions on which the general population hold misconceptions about the effects of brain injury, i.e., overall ability/performance and response latency.



Brain damage, Central nervous system