Play...What's the Point?

Posted: 24/06/2016 @ 13:29PM

With the academic year coming to a close I imagine many of you out there will have resorted to watching cute videos of baby animals playing together on the internet as a means of relieving stress. A personal favourite of mine being animals playing in the snow. Even Darwin commented that “Happiness is never better exhibited than by young animals, such as puppies, kittens, lambs, &c., when playing together, like our own children” (The Descent of Man and Selection in Relation to Sex pp. 448). But what is play and why do animals do it?

First off, we need to consider what play behaviour actually is? In 2005, Burghart came up with five key criteria that a behaviour must meet in order to qualify as ‘play’:

The behaviour is not apparently functional.
The behaviour is voluntary, spontaneous, and pleasurable to those participating.
The behaviour differs from the serious performance of similar behaviours exhibited by adult individuals in some structural or temporal manner.
The behaviour is often repeated but results in different situations and outcomes.
The behaviour only occurs when the individual is safe, healthy, fed, etc.

The first of these criteria, however, poses an interesting dilemma. We all know that selection favours traits that increase an individual’s chances of passing its genetics on to the next generation, a concept we generally term ‘fitness’. It’s one of the four key processes driving evolution, with less successful traits being outcompeted and removed from the population. And although the costs of play are debated, there can be no argument that there is a range of disadvantages associated with the behaviour. There is the matter of time and energy, which could be spent on forging, hunting, or mating, i.e. traits that could directly lead to increased fitness. Playing individuals also risk being spotted by predators, losing contact with the rest of their group, and even physical injury from there surrounding or play-mates. So if play is costly, and not ‘apparently functional’, how is it that it has remained a very prevalent behaviour across the animal kingdom?

It can argued therefor that there is some short-term or long-term benefit to play, great enough to outweigh these costs. Play is often more frequent in the juveniles of a species; those that are developed enough to engage in play activities but young enough that the aforementioned costs can be reduced by parental provisioning and protection. This has led many to argue that there must be some long-term benefit to play, or else we would observed similar levels of play in adult individuals. Others, however, believe that any benefit received from playing must be nearly instantaneous, or else individuals would not invest the costs for the sake of a benefit they will only receive if they actually make it to adulthood. While these arguments may seem contradictory, they are unlikely to be mutually exclusive. This is because not all play behaviour within the animal kingdom are the same. They differ in structure, in purpose, and are therefore likely to have different evolutionary origins.

Locomotion play includes any solitary behaviour in which the performer deliberately handicaps themselves in a way not seen under any other situation. For example tail chasing, head tossing, and bounding on the spot repeatedly are all recognised to be forms of locomotion play. Suggestions for the purpose of locomotion play tend to revolve around learning to ‘expect the unexpected’, that is, to practice rapid decision making and recovery of body function in novel, potentially life threating situations. This logic is backed by the observation that animals tend to play more in ever changing or novel environments (such as snow!). Other theories for locomotory play include the development of complex coordination and balance skills, maintenance of the musculoskeletal system, and acknowledgment of changing body dynamics as individuals grow and mature.

Object play, i.e. playful exploration and interaction with an inanimate object, is likely to have similar benefits to those of locomotion. Not only is the individual provided with an opportunity to learn about the particular object, and exercise their cognitive abilities by using the object, but also practice the regulation of emotions experienced when presented with something new or unfamiliar. Such understanding could potentially increase awareness in stressful situations and allow individuals to make beneficial judgements rather than resort to panic.

Finally, social play with both siblings and adults, is likely to help individuals develop social skills that will be key for adult interactions in an environment where transgressions from the accepted norm are easily forgiven. Play fighting for example, can be identified where self-handicapping by one or more of the individuals results in a variety of fight outcomes, often with the consequences of losing the fight being restrained compared to those of losing a real fight.

While social play provides first-hand experience that may be useful for asserting dominance later on, I propose that it also allows individuals to improve the precision of their assessment ability when it comes to deciding when, and whom, to fight. My current research investigates if the extent of play experience an individual undergoes during development improves their ability to make accurate predictions about potential fight outcome before they engage in escalated (and costly) levels of conflict later in life. So hopefully by the end of my PhD I will be able to shed a little more light onto the evolutionary context of those adorable kitten videos!