Play-Fighting in Animals
Aggression is found throughout the animal kingdom and occurs between members of the same and different species. Depending on the species and the setting, intraspecies aggression can serve several functions, including obtaining food and other resources, gaining access to mates, defending territories, and establishing and maintaining position in a dominance hierarchy. Interspecies aggression can function to subdue prey and fend off their counterattacks, defend against predators, and defend others -- especially the young. Selection pressure for the development and refinement of fighting skills has likely been significant, given the importance of the previously mentioned activities for survival and reproductive success.
Because fighting skills undoubtedly improve with experience and practice, many biologists (e.g., Farentinos, 1971; Symons, 1978) have argued that the young of many species engage in play-fighting as a way of developing and refining their fighting skills. The main basis for this argument is that play-fighting is made up of elements of adult aggression that differ in structure, vigor, or intensity -- presumably in ways that facilitate learning (e.g., Aldis, 1975; Fagen, 1981). Others, in contrast, have argued that the similarities with serious aggression are superficial (e.g., Pellis & Pellis, 1998; Poole, 1966), and that play-fighting might serve other functions, such as social bonding or establishing dominance hierarchies. This issue has been the subject of much discussion and debate, but before turning to functional issues, we review the literature on the structure of play-fighting. This information -- along with information on play partners and gender differences in play-fighting (see later discussion) -- provides data for evaluating some of the numerous functional hypotheses that have been developed concerning play-fighting.
Although some theorists prefer to refer to play-fighting behaviors as immature forms of aggression (e.g., Havkin & Fentress, 1985; Lazar & Beckhorn, 1974), most argue that play-fighting and serious aggression are independent behavior patterns, each under the control of separate neuro-
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