Shared responsibility promotes the benefit of interactive decision- making in novices: A hyperscanning study

Social interaction is ubiquitous. It is widely accepted that social interaction, such as social decision-making, can promote individual's ability and performance (the so-called "interaction benefit"). For example, it was reported that individuals gained more when making a joint decision with conspecifics. Little is known, however, whether and how this interaction benefit during decision making can be biased by shared responsibility (i.e., sharing the results of joint decision-making) between the interacting agents. To address this question, the present study used the dot location estimation task (i.e., an adapted paradigm for social decision-making) and functional near-infrared spectroscopy (fNIRS) hyperscanning (i.e., the measurement of two or more brains simultaneously) technique to investigate the impact of shared responsibility on social decision making. A total number of 70 participants were recruited, forming 35 same-gender dyads. Each dyad included one "expert" and one "novice" (differentiated based on their performance during an initial estimation of dot locations). The fNIRS optodes were placed over prefrontal and right temporo-parietal regions, with 23 channels for each participant. Our results showed that, on the behavioral level, only the novice in a dyad benefited from interaction; also, compared to the non-shared-responsibility condition, novices obtained a higher level of interaction benefit in the shared-responsibility condition. The dyad tended to adopt a "equality strategy" (i.e., decision-making is based on both one's own thought and the partner's suggestion) when sharing responsibility. On the brain imaging level, interpersonal brain synchronization (IBS) within expert-novice dyads in the prefrontal and right temporoparietal regions were detected during social decision-making. More importantly, novices showed stronger IBS in the frontal pole for the shared-responsibility condition (vs. non-shared-responsibility condition). The enhancement of frontal pole IBS positively predicted interaction benefit during social decision-making. Finally, both interaction benefit and frontal pole IBS were selectively correlated with differential performance between novices and experts during the initial estimation of dot locations. These results suggest that sharing the results of joint decision-making can promote the benefit of interactive decision-making in novices. Interpersonal synchronization of frontal poles might serve as a potential brain mechanism. These findings have implications for decision-making, social-cognitive processes, and clinical practice.