Background & Aims
Engaging in a demanding cognitive task can reduce concurrent pain, which is referred to as distraction hypoalgesia(1). Distraction hypoalgesia may occur by recruiting working memory load(2), thus leaving fewer cognitive resources to the processing of pain. Monetary rewards have been shown to amplify this effect by increasing task performance(3). At the same time, cognitive effort is felt as aversive and costly(4) to the point where individuals sometimes prefer to receive physical pain rather than to engage in a demanding cognitive task(5). Therefore, engaging in cognitive effort may help alleviate pain, but only up to a certain point. Our study aimed to 1) investigate the limits of cognitive demand in distraction hypoalgesia and to 2) alleviate the aversiveness of cognitive effort and enhance hypoalgesia using monetary rewards.
Methods
10 pain-free adults were recruited to participate in our study. Participants performed a demanding cognitive task, the 2-back task, at three levels of difficulty (low, medium, and high) while receiving painful thermal stimulations for a given monetary reward ($0 or $20) that they could win if they performed well on the task. Crucially, the pain level (40/100 VAS) and the medium difficulty level of the 2-back task (75% accuracy) were both calibrated to each participant. The low and high difficulty levels of the task were fixed for all participants. After each trial, participant rated the level of pain they experienced on a VAS. After half of the trials, participants rated the subjective demand associated with the task (effort, negative affect, and difficulty). We performed repeated measures ANOVAs to assess the effect of difficulty and reward on pain ratings, task performance, and subjective demand.
Results
We found a significant main effect of difficulty on pain ratings (F(2, 354) = 14.02, p < .001). Post-hoc tests revealed that pain ratings were significantly lower for medium compared to low difficulty (p < .001), but there was no significant difference in pain ratings between medium and high difficulty (p = .78). We also found a significant main effect of reward on pain ratings (F(1, 354) = 5.12, p = .02), revealing that pain ratings were significantly lower on rewarded ($20) compared to non-rewarded trials ($0). We found no significant interaction effect of difficulty and reward on pain ratings (F(2,354) = 0.621, p = 0.54). Results of task performance and subjective demand will also be discussed.
Conclusions
Our findings suggest that engaging in a demanding cognitive task can reduce concurrent pain. Contrary to our hypothesis, performing the task at high difficulty did not disrupt the hypoalgesic effect of the task, suggesting that participants were still able to use a highly demanding and potentially frustrating task to distract themselves away from the pain. Our findings also suggest that monetary rewards may enhance the hypoalgesic effect of distraction by increasing motivation to engage in the task, regardless of its difficulty. Overall, both cognitive demand and motivation appear to play a crucial role in distraction hypoalgesia, yet their interaction remains unclear.
References
(1) Buhle, J., & Wager, T. D. (2010). Performance-dependent inhibition of pain by an executive working memory task. Pain, 149(1), 19–26. https://doi.org/10.1016/j.pain.2009.10.027
(2) Legrain, V., Damme, S. V., Eccleston, C., Davis, K. D., Seminowicz, D. A., & Crombez, G. (2009). A neurocognitive model of attention to pain: Behavioral and neuroimaging evidence. Pain, 144(3), 230–232. https://doi.org/10.1016/j.pain.2009.03.020
(3) Vogel, T. A., Falk, C. F., Otto, A. R., & Roy, M. (2022). Distraction from pain depends on task demands and motivation. PAIN Reports, 7(6), 1-8. https://doi.org/10.1097/PR9.0000000000001041
(4) Kool, W., McGuire, J. T., Rosen, Z. B., & Botvinick, M. M. (2010). Decision making and the avoidance of cognitive demand. Journal of Experimental Psychology: General, 139(4), 665–682. https://doi.org/10.1037/a0020198
(5) Vogel, T. A., Savelson, Z. M., Otto, A. R., & Roy, M. (2020). Forced choices reveal a trade-off between cognitive effort and physical pain. eLife, 9, 1–18. https://doi.org/10.7554/eLife.59410