The Effect of Positive Emotions on Prosocial Behavior During Ego-Depletion: Evidence From fNIRS

Purpose: The psychological and neural mechanisms between relieving ego depletion and prosocial behavior have yet to be clearly explored. To address this, we combined behavioral experiments and fNIRS to explore how positive emotions promote prosocial tendencies under ego depletion. Methods: In Experiment 1, 119 college participants (Mage=19.7 +/- 1.46) completed a dual-task self-control paradigm, confirming that ego depletion negatively impacts prosocial behavior. Experiment 2 involved 48 college participants (Mage=20.26 +/- 2.06) and combined behavioral tasks with functional near-infrared spectroscopy (fNIRS) to examine how positive emotions mitigate ego depletion and enhance prosocial behavior. Results: Experiment 1 showed that participants in the low ego depletion group had a significantly higher bonus allocation amount than the high ego depletion group (t (62) =-2.24, p < 0.05). Experiment 2 showed that after both groups completed the ego depletion task, participants in the positive emotion group allocated significantly higher bonus amounts than those in the neutral emotion group (t (46) =2.06, p <0.05). And the /3 values for channel ch15 (right dorsolateral superior frontal gyrus) and channel ch20 (right medial superior frontal gyrus) were significantly higher in the positive emotion group compared to the neutral emotion group (p < 0.05). The /3 value for channel ch7 (left medial superior frontal gyrus) was also higher in the positive emotion group, approaching statistical significance (p = 0.068). Conclusion: Those findings revealed that high ego depletion reduced prosocial behavior. Additionally, positive emotions alleviated ego depletion and promoted prosocial behavior by activating the medial superior frontal gyrus (SFGmed) and right dorsolateral superior frontal gyrus (SFGdor) negatively.