On knowing it’s only play: The role of play signals in play fighting

play fighting in many species contains behavioral elements of direct aggression; that is, those behavior patterns that are used to threaten and contact opponents. Although many investigators have alleged that there are play signals that can be used to unambiguously distinguish playful from nonplayful aggression, the existence of such signals is mainly anecdotal and correlational. For most species, such signals are either not present, or are not present with sufficient regularity to function as unambiguous markers of play. In most playful encounters, participants seem able to use contextual cues to assertain whether the actions of the partner are affiliative or not. Where play promoting signals do appear to exist, they are often general purpose affiliative signals rather than ones specific to play. Such signals are most often associated with situations where the playful intentions of the performer may be ambiguous to the recipient. In these situations, such signals appear to be crucial in avoiding escalation to serious aggression. The danger of escalating from play to aggression is most often reported as animals become sexually mature and stronger. Also, it is in early adulthood that members of a social group compete for dominance. In these situations, a signal “this is play ” may not be sufficient. Instead, signals that can retroactively appease a play partner with “I was only kidding, ” may be very important so as to manipulate, and thus obfuscate, the true intent of the action. When present, the signals occurring in play are highly variable inform and context, which is what would be expected for such subtle social manipulation. We suggest that species with more complex social relationships, where individuals are likely to probe and test their relationships with play fighting, are most likely to be the ones that make the most sophisticated use of such signals.