Why would evolution bother? Play burns energy, distracts from food and safety, and draws the attention of predators. Animals that play anyway, from rats to ravens to us, are paying a real cost. They must be getting something back.
They are. Play is how young brains practise being an adult in a world where mistakes are cheap. It's not the opposite of learning. For children, it's one of the main ways learning happens.
What counts as play
Researchers define play less by the activity than by the attitude. A common definition calls it behaviour that is "freely chosen, personally directed, intrinsically motivated." The same game of football is play at the park and something else at a drill-heavy training session where a coach picks every move.
Play comes in many forms, and each one trains something different:
| Kind of play | Example | What it seems to build |
|---|---|---|
| Physical and rough-and-tumble | Chasing, wrestling, climbing | Strength, coordination, reading other people's limits |
| Pretend | "You be the doctor, I'm the patient" | Imagination, language, seeing through others' eyes |
| Object and building | Blocks, sand, taking things apart | Problem-solving, early maths and physics |
| Games with rules | Tag, cards, made-up games | Self-control, fairness, negotiating |
| Risky | Heights, speed, exploring alone | Judging risk, managing fear |
What the evidence says
In 2018 the American Academy of Pediatrics published a clinical report titled The Power of Play. Its message was blunt: "Play is not frivolous." The report argued that play with parents and peers builds the social, emotional, language and self-regulation skills behind executive function, the mental toolkit for setting goals, holding information in mind and resisting distractions. It went as far as encouraging paediatricians to write children a "prescription for play" at check-ups.
Play is not a break from development. In childhood, it is development.
Play also shows up in the brain. Many mammals, including rats and cats, play most around puberty, the period when the brain is reorganising. The researcher Sergio Pellis and colleagues have suggested that play may help shape and prune the developing brain into a more efficient adult one. Animal work like this can't be copied straight onto children, but it points the same way.
Pretend play stretches thinking in its own way. A child who says "this stick is a horse" has to hold two ideas at once, what the stick is and what it stands for. Vygotsky argued that this kind of play is where children first learn to separate a symbol from the thing it stands for, the same move that reading and maths later demand.
The risky part
Many parents' instinct is to remove risk entirely. The evidence suggests that has a cost too. A 2015 systematic review of 21 studies on risky outdoor play (climbing, rough-and-tumble, exploring without adults hovering) found overall positive effects on children's health, most commonly physical activity, but also on social health and behaviour. The authors called for better-quality studies, but concluded that their findings support promoting risky outdoor play.
The key distinction is between risk and hazard. A risk is something a child can see and choose to take on, like a tall climbing frame. A hazard is a danger they can't see or judge, like a rotten branch or a busy road. Remove the hazards; leave some of the risk.
The open question
Has childhood lost too much play? The psychologist Peter Gray, author of Free to Learn (2013), argues that unstructured, child-led play has declined sharply over recent generations as schooling, organised activities and adult supervision expanded, and that this has contributed to rising anxiety and depression among young people. Others, notably the social psychologist Jonathan Haidt, put more of the blame on smartphones and social media, while also calling for more free play. Gray, for his part, rejects the smartphone explanation.
Both cases rest heavily on trends over time, which are hard to untangle. What's less disputed is that children benefit from regular time to play freely, outdoors where possible, without a curriculum attached.
The takeaway
Play is evolution's training ground: freely chosen, intrinsically motivated activity in which children practise physical, social, emotional and thinking skills where mistakes cost little. Paediatric experts now treat it as essential, not optional, for building executive function and relationships. A sensible amount of risk is part of what makes it work. How much the decline of free play explains today's youth mental-health trends is still debated.
Try this: this week, give a child (or yourself) 30 minutes of play with no goal, no screen and no adult in charge of the rules. If you're the adult, your only job is to stay nearby, remove real hazards, and resist the urge to direct.
Sources & Further Reading
Sources
- Panksepp, J. & Burgdorf, J. "50k-Hz chirping (laughter?) in response to conditioned and unconditioned tickle-induced reward in rats." 2000.
- Definition of play ("freely chosen, personally directed, intrinsically motivated"): UK National Playing Fields Association, 2000; play peaking around puberty in many mammals (John Byers) and Pellis's research on play and brain development: summarised in Wikipedia's "Play (activity)."
- Yogman, M. et al. "The Power of Play: A Pediatric Role in Enhancing Development in Young Children." Pediatrics, 2018.
- Brussoni, M. et al. "What is the Relationship between Risky Outdoor Play and Health in Children? A Systematic Review." International Journal of Environmental Research and Public Health, 2015.
- Gray, P. Free to Learn, Basic Books, 2013; Haidt, J. The Anxious Generation, 2024.
Go deeper
- 📘 Free to Learn — Peter Gray (the case for self-directed play, passionately argued)
- 📘 Play — Stuart Brown (a psychiatrist on why play matters for adults too)
- 🌐 The Power of Play — AAP clinical report (free full text)