Does Effort Suppress Cognition After Traumatic Brain Injury? A Re-Examination of the Evidence for the Word Memory Test

Abstract

Green, Rohling, Lees-Haley, and Allen (2001) suggested that scores on a test of “effort,” the Word Memory Test (WMT), explains more variance in outcome after brain injury than does injury severity. As a consequence, Green and colleagues recommend using the WMT to control for sub-optimal effort in neuropsychological evaluations and group research. We re-examine the evidence for their conclusions and argue that identifying a larger proportion of explained variance is not in itself evidence of validity unless the premise to be proven is already assumed, namely, that the test is a valid measure of effort. Instead, the crux of Green and colleagues claim for the validity of the WMT implies an interaction between effort and injury severity on outcome scores, although the specific interaction has not been tested in their previous research. We failed to find any evidence for this interaction in a sample of 100 Australian litigants. We conclude that our data do not support the view that effort, as measured by the WMT, interacts with injury severity to suppress cognition after brain injury.

Acknowledgments

This research was supported by a project grant from the Australian National Health and Medical Research Council. The authors wish to thank Peta Minton, Heidi Newitt and Leonie Simpson for assistance with data collection and manuscript preparation.

Notes

Note. Sample size for each subset of data is shown in parentheses for each score. Also shown is the mean WMT-IR score and the percentage of each subsample who passed or failed the WMT.

Note. Also shown is the percentage of the sample who passed or failed the Word Memory Test stratified by the duration of PTA.

A version of this paper was presented at the Association of Forensic Neuropsychology Conference, Institute of Child Health, London, February, 2004.