Cooperation moderates the impact of effort on reward valuation.

Effort is valuable, but researchers have different opinions on whether effort can reduce or increase the valuation of rewards. The effect of cooperation on reward valuation also remains unclear. In this study, we conducted two experiments to examine the effect of effort on reward valuation (Experiment 1) and whether this effect can be influenced by cooperation (Experiment 2), using electroencephalogram (EEG) technology. We found that when participants worked alone, they generated a larger feedback-related negativity (FRN) amplitude for losing rewards than for gaining rewards, with more effort resulting in larger FRN amplitudes for losing rewards. However, when participants worked together with a partner, there was no significant difference between the amplitude for gaining rewards and that for losing rewards during low-effort tasks. Nevertheless, for high-effort tasks, the FRN amplitude for losing rewards was significantly larger than that for gaining rewards. Moreover, in both experiments, we found larger N1 amplitudes for gaining rewards than for losing rewards. Our ERP results suggest that in the early stage of processing, people pay extra attention to rewards, after that the effort level influences their reward valuation. In addition, cooperation regulates the reduced valuation of losing rewards only when people invest low effort.