Abstract and Summary
We evaluate the claim that social grooming is altruistic because it occupies time that could otherwise be spent feeding. Time spent feeding is shown (1) to be correlated negatively with time spent resting and (2) not to be correlated with social time for two genera of Old World monkeys. Social time thus tends to be conserved in the face of increasing demand for feeding time at the expense of resting time. This suggests either that the altruistic costs of grooming are trivial or that grooming is more valuable to the groomer in terms of benefits to be derived from, for example, the formation and maintenance of alliances.