A central feature of rough-and-tumble play is reciprocity, requiring that the competition to win be attenuated by the need to maintain cooperation. This feature of rough-and-tumble play appears to be put to good use during childhood for the development of nuanced social skills, and can be used to good effect, throughout the life cycle, to deal with ambiguous social situations. The experimental and comparative literature on non-human animals provide a guide both for characterizing the brain mechanisms involved and for identifying the behavioral rules by which such play can be effectively deployed. © 2011 by Oxford University Press, Inc. All rights reserved.