Play is an instinct that unites species
PARIS : Imagine a rat hiding under a plastic box while a human searches for it, then erupting with joy when it's been found. This is not a scene from the 'Ratatouille' movie, but the protocol of a study published in 2019 in the journal Science.
Neuroscientists at Humboldt University of Berlin succeeded in teaching six young rats to play hide-and-seek.
To begin with, the researchers let them explore their playground, a 30-square-metre room dotted with boxes and partitions serving as hiding places.
Before the experiment began, researcher Annika Reinhold had accustomed the rodents to her presence by stroking them, tickling them and chasing them with her hands.
She then taught them the role of the seeker: to do this, she would lock a rat in a box, go and hide in a corner of the room, then reward it with tickles if it came to join her.
When a rat was free from the start, it was up to the animal to play hide-and-seek. It then had to quickly choose a hiding place and stay there quietly until being discovered.
The study showed that rats can effectively learn how to play hide-and-seek. Better still, they understand the rules, choose strategic hiding places – the most opaque, the most discreet – and know how to make themselves go unnoticed by remaining silent.
And when the moment comes to be discovered, they erupt with joy, leaping with gusto and uttering the little ultrasonic vocalisations typical of pleasure.
The rats also tend to prolong the game. As soon as they're discovered, they immediately scurry off to hide elsewhere, as if to restart the game. They even postpone the moment of reward stroking, obviously preferring to keep the game going a little longer.
For them, play is a social activity, a voluntary activity and clearly a source of pleasure.
Play is much more than just a way of letting off steam; it's a powerful tool for building relationships. (Envato Elements pic)
Play as a sign of intelligence
In apes, play becomes strategy. Researchers from the University of California Los Angeles, the Max Planck Institute of Animal Behaviour, Indiana University, and the University of California San Diego, identified playful behaviours that are surprisingly similar to those of human children.
The young monkeys have fun provoking adults, poking them, waiting for their reaction… then doing it again, as if anticipating the effects of their actions.
In a study published in 2024 in the journal Proceedings of the Royal Society B, the scientists suggest that this taste for teasing is anything but trivial. It may be a sign of the existence, in humankind's last common ancestor, of the cognitive prerequisites necessary for playful teasing.
After all, playing the clown can be a complex business. It implies understanding the other person, anticipating their reactions, and wanting to maintain a bond.
In this respect, play is much more than just a way of letting off steam; it's a powerful tool for building relationships.
For primatologist Frans de Waal, these playful jousts reinforce social hierarchies while strengthening group cohesion. In short, apes, like humans, play to help them live better together.
The natural history of animals abounds in observations of games. Play is widespread among mammals, but less common among birds, with the exception of corvids, where it is clearly evident.
In a study published in 2019 in the journal Current Biology, American and Australian researchers claim that New Caledonian crows derive pleasure from manipulating objects, which improves their mood and optimism – a cognitive experience reminiscent of our own taste for intellectual challenges.
Whether it's elephants having a friendly tussle, or crows gliding across snow-covered rooftops, many animals love to play, mostly out of sheer pleasure. (Envato Elements pic)
An evolutionary drive for play
Rats, great apes, crows… the list of playful animals grows longer as research continues. But why do so many species play?
No doubt because play has many functions, from motor development and social learning to bonding and cognitive stimulation.
Neuroscience suggests that the brains of mammals and certain birds are 'programmed' to play.
Experiments with dolphins and crows have shown that the most playful individuals are also the most curious, the most adaptable, and sometimes even the most innovative.
This suggests that play is a gateway to creativity and problem-solving.
But play can also be about having fun. Whether it's dolphins surfing the waves for no apparent purpose, elephant calves chasing each other around a tree trunk, or crows gliding across snow-covered rooftops, many animals love to play, mostly out of sheer pleasure.
Owners of cats, dogs and even rodents are well aware of this. As are scientists, who have observed this behaviour in fish, frogs, lizards and birds.
But what about insects? Are their cognitive capacities sufficiently developed for them to want to have fun?
Apparently so, according to a study published in 2022 in the journal Animal Behaviour. It showed that bumblebees enjoy rolling wooden balls for no reason or reward – just for the fun of it.
Perhaps play is not a luxury reserved for superior species, but an evolutionary necessity rooted in the biology of living things, whether it's a kitten bouncing around, a dog wagging its tail when it sees a ball, or even a magpie playing with a cork.
These innocuous moments speak volumes about the emotional and cognitive richness of the animal world. And they remind humans that pleasure is a universal language.
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