Pleasant fragrance modulates dyadic social sharing of positive emotion: Sharer-centered socioemotional enhancement effect and its neural couplings.

Despite the widespread use of fragrances for interpersonal engagement, it remains unclear whether it actively shapes the socioemotional experience of interactive partners during social sharing. The present study combined with functional near-infrared spectroscopy system (fNIRS) and examined whether during the positive emotion sharing, the presence of fragrances specifically improves the emotional states and interpersonal outcomes of interaction partners, and further explored the inter-brain coupling mechanism underlying these effects. Thirty-eight mixed-gender stranger dyads (sharer vs. listener) were assigned to either a fragrance condition or a control condition and completed experimental social sharing tasks about neutral, happy, nostalgic, and proud events. Participants' emotional states, interpersonal relationship ratings, and cortical activities over temporoparietal and inferior frontal regions were recorded. Our results showed that during happy sharing, sharers with a pleasant fragrance reported more positive emotions, stronger sense of belonging, and also showed stronger functional connectivity between the right inferior temporal gyrus and the right inferior frontal gyrus. Pleasant fragrance enhanced inter-brain synchrony (IBS) between the sharer's inferior frontal gyrus and the listener's angular gyrus more during happy sharing than sharing proud events. Nostalgic sharing, however, unexpectedly tended to reduce listener's positive emotions. These findings suggest that a pleasant fragrance drives both behavioral and neural benefits during positive emotion sharing, boosting interpersonal outcomes and neural resonance in socioemotional-related regions.