Yamagishi et al. (2017)

Yamagishi, T. (山岸俊男), Matsumoto, Y.(松本良恵), Kiyonari, T.(清成透子), Takagishi, H.(高岸治人), Li, Y.(李楊), Kanai, R., & Sakagami, M. (2017). 
Response time in economic games reflects different types of decision conflict for prosocial and proself individuals 
経済ゲームにおける反応時間は向社会的と向自己的個体の決定コンフリクトの違いを反映する 
Proceedings of the National Academy of Science of the United States of America (Published online before print May 30, 2017) doi: 10.1073/pnas.1608877114 

Behavioral and neuroscientific studies explore two pathways through which internalized social norms promote prosocial behavior. One pathway involves internal control of impulsive selfishness, and the other involves emotion-based prosocial preferences that are translated into behavior when they evade cognitive control for pursuing self-interest. We measured 443 participants’ overall prosocial behavior in four economic games. Participants’ predispositions [social value orientation (SVO)] were more strongly reflected in their overall game behavior when they made decisions quickly than when they spent a longer time. Prosocially (or selfishly) predisposed participants behaved less prosocially (or less selfishly) when they spent more time in decision making, such that their SVO prosociality yielded limited effects in actual behavior in their slow decisions. The increase (or decrease) in slower decision makers was prominent among consistent prosocials (or proselfs) whose strong preference for prosocial (or proself) goals would make it less likely to experience conflict between prosocial and proself goals. The strong effect of RT on behavior in consistent prosocials (or proselfs) suggests that conflict between prosocial and selfish goals alone is not responsible for slow decisions. Specifically, we found that contemplation of the risk of being exploited by others (social risk aversion) was partly responsible for making consistent prosocials (but not consistent proselfs) spend longer time in decision making and behave less prosocially. Conflict between means rather than between goals (immediate versus strategic pursuit of self-interest) was suggested to be responsible for the time-related increase in consistent proselfs’ prosocial behavior. The findings of this study are generally in favor of the intuitive cooperation model of prosocial behavior. プレスリリース（玉川大学）はこちら．