13 Money versus Feedback: Comparing Reward Types and Frequency on Cognitive Fatigue

Objective:Cognitive fatigue (CF) is a common, yet poorly understood symptom in neurological disorders (e.g., multiple sclerosis, Parkinson’s disease, stroke). Studies show that reward plays a central role in CF. For instance, introducing or increasing reward often improves task performance. It is less clear, however, how reward affects subjective (self-reported) CF (SCF). This study examined the effect of reward type (monetary or performance feedback) and frequency (infrequent or frequent) on SF.Participants and Methods:In an online between-subjects study, 400 participants completed a computerized cognitive switching task and were randomly grouped into one of the five possible groups based on reward condition: [1] infrequent monetary reward, [2] frequent monetary reward, [3] infrequent performancefeedback reward, [4] frequent performance feedback reward, and [5] a no-reward group. SCF was assessed using the Visual Analog Scale of Fatigue (VAS-F) during the task. Mixed effects models were used to estimate the influence of reward type and frequency on task performance and SCF.Results:We found that the monetary groups were significantly faster (p<.001) compared to the feedback and no-reward groups, and that the frequent group was faster (p=.05) compared to the infrequent group. Reward type and frequency did not have a significant effect on VAS-F scores. However, when we looked at each reward group, we found that the monetary-infrequent reward group was associated with a decrease in VAS-F scores on average compared to the no-reward group (p=.04).Conclusions:The type and frequency of reward influence aspects of task performance (response time but not accuracy). Findings suggest that money had a greater effect on response time and may decrease SCF in cognitively healthy individuals when provided infrequently. Future studies should examine how these findings translate to clinical populations. Continued work is needed to understand how and which specific behavioral reward manipulations reduce fatigue, which could eventually lead to improved assessment and our ability to target fatigue across clinical populations.