Play and Mate Preference: Testing the Signal Theory of Adult Playfulness.

The overwhelming majority of play research concerns juveniles. However, a full understanding of the phenomenon requires knowledge of play and playfulness across the life spans of those animals, including humans, who play in adulthood. The authors investigate a theory of play based on Darwin's concept of sexual selection that may account for the existence of play among adult humans. The authors hypothesize that playfulness becomes a highly desired characteristic in potential long-term mates but also that the reasons for desiring playful mates differ for males and females. The authors suggest that for males, playfulness in females signals youth and, hence, fecundity; for females, playfulness in males signals nonaggressiveness. They test these hypotheses using mate-preference data. Key words: adult play and playfulness; play and mate preference; play evolution; sexual selectionIf a wild animal habitually performs some useless activity, natural selection will favour rival individuals who devote the time and energy, instead, to surviving and reproducing. Nature cannot afford frivolous jeux d'esprit. Ruthless utilitarianism trumps, even if it doesn't always seem that way. -Richard Dawkins, The God DelusionPlay is quintessential jeux d'esprit, but because nearly all, if not all, mammals, many birds, and members of numerous other species play (Burghardt 2005), it also presents one of evolution's most vexing problems. Play appears to be not only nonutilitarian but is often downright dangerous. It seemingly wastes time and energy, opens players to injury and occasionally even to death, and leads, at times, to a lack of vigilance that may expose them to predation (Bekoffand Byers 1998; Bjorklund and Pellegrini 2002; Fagen 1981; Pellegrini and Bjorklund 2004; Symons 1978; for an alternate view see Martin and Caro 1985; Power 2000). So, why does play exist? In 1998 at a combined meeting of The Association for the Study of Play and the Society for Cross-Cultural Research, one of us-Garry Chick-delivered a keynote address titled "What is Play For? " (Chick 1998, 2001). In it, he expressed his worry about traditional theories of play (as described in, e.g., Ellis 1973) and their failure to explain adequately the existence of play. Most of these theories are outdated and all but useless because they do not lead to testable predictions. Additionally, and as important, they fail to address play and playfulness among adults. (We regard play as the behavioral manifestation of playfulness that, in turn, is the propensity to engage in play.) In contrast, Chick proposed a theory, based on Darwin's concept of sexual selection, that is not only relevant to adult play and playfulness but also permits the generation of testable hypotheses. Specifically, Chick postulated that play and the personal characteristic of playfulness, among adult humans, send signals, or messages, to the opposite sex of important information regarding the signaler's suitability as a long-term mate. Moreover, the content of the signals sent by males and by females differs. Through play and playfulness, males signal their nonaggressiveness while females signal their youth and fecundity. This article presents and tests hypotheses based on Chick's signal theory of adult playfulness.Proximate and Ultimate CauseChick's proposal rested on an explicitly evolutionary perspective. Therefore, we distinguish two types of explanation we believe apply to play and playfulness to understand them from an evolutionary perspective. In biology, proximate cause refers to something immediately responsible for some other action or event. This contrasts with ultimate cause, generally a reference to an evolutionary explanation. In an influential 1961 paper, biologist Ernst Mayr wrote that proximate and ultimate causes deal with how and why questions respectively. For example, how do birds determine when to migrate? They migrate because they have internal biological clocks that alert them to fly north (in the Northern Hemisphere) for reproduction and south for the winter. …