The Purpose of Play

Why do so many young animals spend time chasing, wrestling, and exploring? From an evolutionary perspective, play presents a puzzle.

Natural selection is expected to favour behaviours that improve survival and reproduction, yet play consumes time and energy without any immediate reward. But play actually does serve a very important purpose, giving young animals a chance to practise the behaviours they will later rely on to find food, avoid predators, compete for mates, and navigate life in complex social groups.

Source: From a timid polar bear to a snoozing capybara – 20 adorable baby animals captured on camera | Discover Wildlife 

In the first episode of The Wild Minds mini-series, Clara and Carolina are joined by Prof. Nacho Sanguinetti to explore how play provides a unique window into the animal mind. From its evolutionary significance to the neural mechanisms that underpin flexible behaviour, they discuss how play shapes the brain and builds behavioural flexibility and how studying animals in their natural environments is key to understanding these rich play behaviours. 

Many forms of play refine the motor and sensorimotor skills that animals depend on later in life. Young predators, for example, spend countless hours chasing, pouncing, wrestling, and stalking one another. Although these games appear aimless, they allow animals to repeatedly practise balance, coordination, timing, and precise movement. By the time these skills become essential for catching prey or escaping danger, much of the underlying motor control has already been developed through play.

Play also helps animals develop social competence, an ability acquired early in development. Games of chase, wrestling, and fighting teach animals when to cooperate, when to compete, and how to recognise others' intentions and signals. Experimental studies highlight just how important these early experiences can be. For example, Samuni and colleagues [1] found that juvenile chimpanzees deprived of play opportunities later struggle to interpret social cues and adjust their behaviour to different partners, while long-term studies of chimpanzees have found that those engaging more frequently in social play go on to form stronger social relationships as adults [2]. Allowing animals to practise these interactions prepares them for the complex social lives they will navigate as adults.

"Games of chase, wrestling, and fighting teach animals when to cooperate, when to compete, and how to recognise others' intentions and signals... allowing animals to practise these interactions prepares them for the complex social lives they will navigate as adults."

Source: Cognition and Culture in Chimpanzee Play | Homepage Alex Mielke 

Play also encourages animals to explore without knowing what they might discover. This open-ended exploration develops cognitive flexibility, the ability to adapt behaviour when familiar strategies no longer work. These principles extend to other exploratory behaviours, including tool use.  Kenward and colleagues [3] found that New Caledonian crows raised without adult demonstrators still manufactured and used stick tools to retrieve food, showing that sophisticated problem-solving can emerge through exploration rather than imitation alone. Researchers found that successful tool use was preceded by months of playful manipulation of twigs, leaves, and other objects, during which young birds gradually discovered new ways of interacting with their environment.

Experience-dependent changes in the developing brain underpin the behavioural benefits of play. Studies of rough-and-tumble play [4] in juvenile rats have shown that play is intrinsically rewarding, with the motivation to engage in play driven by dopamine signalling within the mesolimbic reward system. Researchers found that manipulating dopaminergic signalling alters the effort rats are willing to expend to gain access to a play partner, demonstrating that dopamine regulates the motivation to seek play rather than the pleasurable experience itself. These repeated social interactions, in turn, contribute to the maturation of the medial prefrontal cortex, a region involved in evaluating social cues, selecting appropriate behavioural responses, and adapting behaviour to different partners. 

"Experience-dependent changes in the developing brain underpin the behavioural benefits of play."

Play shapes not only the development of individual brain regions but also the connections and coordinated activity between them. Evidence from studies suggests that subcortical circuits linking the thalamus and striatum contribute to the rapid sensorimotor adjustments required as animals chase, wrestle, and respond to a partner's movements. Cortical regions, including the medial prefrontal and orbitofrontal cortices, appear to refine these interactions by allowing animals to modify their play according to a partner's behaviour, previous experience, and social context [5].

A custom virtual reality system enables rats to navigate the game, Doom, while researchers study learning, navigation, and sensorimotor behaviour. Source: https://ratsplaydoom.com/

Play is a complex behaviour that integrates movement, sensory exploration, social interaction, learning, reward processing, and decision-making; it cannot be fully understood by studying these processes in isolation. Advances in naturalistic behavioural tracking and large-scale neural recording allow researchers to observe animals as they interact freely with their environment, moving beyond laboratory tasks. Rather than isolating individual behaviours, neuroscientists can now investigate how distributed neural circuits coordinate exploration, learning, and social interaction in real time. This shift is changing both the methods that researchers use to understand behaviours and the questions researchers can ask.  How does the brain distinguish playful exploration from purposeful action? Could play be one of the ways that evolution equips animals not only to survive in their environment but also to find their place within it?

source: https://www.bbcearth.com/news/all-fur-and-games-why-do-animals-play

"Could play be one of the ways that evolution equips animals not only to survive in their environment but also to find their place within it?"

By studying play, researchers are beginning to understand that natural selection does not only shape the behaviours animals are born with; it also shapes how they learn. Perhaps the real advantage of evolution is not fixed behaviour but the ability to adapt through experience.

This article was written by Purnima BR and edited by Clara Lenherr.

References

1. Samuni, L., Mielke, A., Crockford, C., & Wittig, R. M. (2024). Social play fosters cooperation in wild adult chimpanzees. Current Biology, 34(24), 5839-5845.e3. https://doi.org/10.1016/j.cub.2024.10.058

2. Pellis, S. M., Pellis, V. C., & Bell, H. C. (2010). The Function of Play in the Development of the Social Brain. American Journal of Play, 2(3), 278–296. https://eric.ed.gov/?id=EJ1069225

3. Kenward, B., Rutz, C., Weir, A. A. S., & Kacelnik, A. (2006). Development of tool use in New Caledonian crows: Inherited action patterns and social influences. Animal Behaviour, 72(6), 1329–1343. https://doi.org/10.1016/j.anbehav.2006.04.007

4. Pellis, S. M., Pellis, V. C., Ham, J. R., & Achterberg, E. J. M. (2022). The rough-and-tumble play of rats as a natural behavior suitable for studying the social brain. Frontiers in Behavioral Neuroscience, 16. https://doi.org/10.3389/fnbeh.2022.1033999

5. Bell, H. C., McCaffrey, D. R., Forgie, M. L., Kolb, B., & Pellis, S. M. (2009). The role of the medial prefrontal cortex in the play fighting of rats. Behavioral Neuroscience, 123(6), 1158–1168. https://doi.org/10.1037/a0017617