Financial Incentives Influence ImPACT Validity Indicator Measures but not Cognitive Composite Scores

Journal of the International Neuropsychological Society. 2018 Nov;


Rabinowitz, A. R., Merritt, V. C., Guty, E., Meyer, J., Greenberg, L. and Arnett, P..



Objective: Interpreting changes in cognitive performance across baseline and post-concussion evaluations is complicated by poor understanding of how incentives, such as return-to-play, may influence performance. This study examines the influence of an anticipated financial incentive on two sets of outcomes from the ImPACT computerized concussion battery: 1) Cognitive Composite scores (CCs), meant to serve as measures of cognitive function, and 2) Validity Indicator indices (VIs), proposed as indicators of test invalidity. Participants and Methods: 82 uninjured college students, randomized into two groups, completed a concussion assessment battery including ImPACT. The Control group received standard administration instru tions. The Incentive group was told they would receive $20 if their scores ranked in the top third of students who had completed the test. Examiners were blinded to condition. No financial incentives were provided, and all participants were debriefed at the end of the session. Results: Independent samples t-tests revealed no significant differences between Incentive and Control groups on any of the CCs—Verbal Memory: t(79)=1.29, p=.20; Visual Memory: t(79), p=.24; Visual Motor Speed: t(79)=.34, p=.75; Reaction Time: t(79)=.79; p=.43. Mann- Whitney U Tests revealed significant differences between groups all five VIs—Impulse Control Composite: U=604, p=.03; Word Memory Learning % Correct: U=1,025, p=.045; Design Memory Learning % Correct: U=1,097, p=.02; Xs & Os Interference Total Incorrect: U=598, p=.02; Three Letters Total Letters Correct: U=1,058.0, p=.02. Conclusions: Expectation of financial incentive did not significantly influence ImPACT’s standard metrics of cognitive function (CCs). However, the Incentive group exhibited significantly better performance on each of the validity indicator indices (VIs). These results suggest that ImPACT CCs are robust to incentive-related changes in effort, and provide support for the VI indices as measures of effort towards testing.

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