The ecological rationality of helping others: Potential helpers integrate cues of recipients' need and willingness to sacrifice

摘要

Why do humans help others? Many theories focus on dimensions like kinship or reciprocity. On their surface, these theories seem unable to explain help directed at fleeting strangers. In response to this puzzle, researchers have proposed that the mind has ecologically rational systems for providing aid. These systems respond to cues that predicted adaptive behavior during human evolution, regardless of whether such cues continue to be predictive in modern environments. In three studies, we test for two cues that might predict whether a potential benefactor will help a potential recipient: the need of the recipient and the extent to which the recipient is willing to sacrifice for the benefactor. Both cues, in ancestral environments, have the potential to predict whether a long-term relationship might be established. Consistent with past research, we find that both cues matter: Needy people and people willing to sacrifice are helped more. However, the cues are not merely additive: In some cases, the cue of need is ignored and only willingness to sacrifice is used. We discuss these results in terms of recent evolutionary theories of emotions.