This is the 2007 version. Click here for the 2017 chapter 08 table of contents.


Fagen (1983) argued that, because play expends energy and creates a risk of injury, it must have counterbalancing benefits, or it would not be positively selected in evolution. What is the adaptive function of play? One hypothesis born out by field studies is that social bonds formed in childhood can be helpful later in life. Smuts, who took the picture of Pandora and Virgil, found friendship did appear to help baboons. Friendships formed in childhood often lasted into adulthood.

What are benefits of play?

Another obvious benefit of play is that it exercises and refines skills to be used in adulthood.

Most play is vigorous, repeated, and often spectacular exercise. Repeated performance of motor tasks in mammals results in a physiological "training response" in which muscles and bones hypertrophy (develop), endurance increases, and the economy and precision of the movements increase.

...In the few species studied, play accounts for almost all vigorous exercise performed by young animals and...many aspects of playfighting are strikingly congruent with exercise programs designed to develop skill in humans. (Byers, 1981)

How do young animals signal that their play attacks are not serious?

Play is often repetitious, and often the play behavior is not carried to its usual conclusions (for example, in play-biting the teeth are not closed), or else the play is exaggerated in form (e.g. the bounding of a kitten). Social play (pouncing, rough-housing) is often preceded by a stereotyped pose or behavior that indicates a lack of serious aggression or intention to harm. Rhesus monkeys have a play-face they make before bothering an adult, while dogs and cats often crouch halfway before pouncing in play.

How do adults start episodes of play with youngsters?

Hinde (1970) pointed out that play behavior is often elicited by an older animal. The lioness twitches her tail and cubs play with it. Female chimpanzees tickle and roll their infants while pretending to bite them. Playing with young offspring is evidently pleasurable to adults, too, in moderate amounts, so these behaviors are mutually reinforcing.

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