Trust Among Siblings is Intuitive

Research on whether prosocial behavior is deliberate or intuitive typically uses decision time in economic games as a proxy for the automaticity of underlying cognitive processes. We investigate the relationship between trust and decision time in a sample with a predicted high baseline level of cooperative behavior and low conflict between self-interested and cooperative motives: biological siblings. Sixty-three full sibling pairs played for money in a one-shot trust game. We found a significant negative linear (rather than quadratic) effect of trust on decision time: the more money a sibling was trusted with, the quicker the decision was made. These results suggest that trust among siblings is intuitive and largely based on automatic and effortless processes.