Nominal kinship cues facilitate altruism.

We investigated whether names in common promote altruistic behaviour, predicting that this would be especially so for relatively uncommon names, for surnames (which are better kinship cues than first names), and among women (who, although less willing than men to help strangers, according to prior research, are also the primary "kin keepers"). We solicited help from 2960 email addressees, with the request ostensibly coming from a same-sex person sharing both, either, or neither of the addressee's first and last names. As anticipated, addressees were most likely to respond helpfully when senders shared both their names (12.3%) and least likely when they shared neither (2.0%), and this was especially true for relatively uncommon names. A shared surname was more effective than a shared first name only if it was relatively uncommon. Women were substantially more likely to reply than men. These results indicate that names elicit altruism because they function as salient cues of kinship.