Paying Back People Who Harmed Us but Not People Who Helped Us: Direct Negative Reciprocity Precedes Direct Positive Reciprocity in Early Development.

The principle of direct reciprocity, or paying back specific individuals, is assumed to be a critical component of everyday social exchange and a key mechanism for the evolution of cooperation. Young children know the norm of reciprocity, but it is unclear whether they follow the norm for both positive and negative direct reciprocity or whether reciprocity is initially generalized. Across five experiments ( = 330), we showed that children between 4 and 8 years of age engaged in negative direct reciprocity but generalized positive reciprocity, despite recalling benefactors. Children did not endorse the norm of positive direct reciprocity as applying to them until about 7 years of age (Study 4), but a short social-norm training enhanced this behavior in younger children (Study 5). Results suggest that negative direct reciprocity develops early, whereas positive reciprocity becomes targeted to other specific individuals only as children learn and adopt social norms.