Exploring the woods, colonizing local hedgerows, or hiking to the river and back again became our default entertainment. Sniffing the air for adventure, we created worlds, fought battles, negotiated treaties and formed alliances. Free time seemed to stretch out in endless supply like fresh air.

When the school year began again, free time shifted to the late afternoon, but was no less an important part of our day. Interrupted by freak homework assignments and, just possibly, a once-per-week piano lesson, our visits to the out-of-doors persisted until winter darkness drove us inside to conjure new worlds and deconstruct each other’s rumpus rooms. Negotiations continued, now intensified by the fug of damp interiors and the urgency of earlier bedtimes.

Enter my own children, and the reality of year round free time has changed. Today’s kids are more likely to have jam-packed schedules filled with the opportunity to master a martial art, speak a second language, train for an Olympic sport, perfect various dance forms, brush up on their coding, cook a gourmet meal, solve a crime, animate a movie, or join the circus.

The diversity of opportunities is positive, but as parents, we are under more and more pressure to enroll our children in the latest activity. As caregivers we want to keep them safe and expose them to a variety of new experiences, but how does this departure from unstructured activities—specifically unstructured play—affect our kids?

Thinkers around the world have started making connections between optimal learning, happiness, and active or free play. Here’s what some are saying.

Play makes our children happier

According to the National Institute for Play (yes, we have one of those), active or free play is the gateway to vitality. Defined as the sort of play that children do without apparent purpose, active play is not scheduled, refereed, or controlled by an adult. In other words, you might be supervising your child during active play, but only from a distance. This isn’t your show, and your child is more or less in charge.

Evolutionary psychologist Dr. Peter Gray points to the decline in active play as the main reason for increased mental disorders diagnosed in children. Anxiety and depression among kids has risen sharply since the 1950s, along with the suicide rate, which has quadrupled for children under the age of 15. In his TED talk about the decline of play, Gray notes that “play is nature’s way of ensuring that young mammals, including young humans, acquire the skills they need to develop successfully into adulthood.” When outside forces control their every move, children instead develop traits like narcissism, fatalism, and other negative attributes. Says Gray, “One thing psychologists know very well is that not having an internal sense of control sets you up for anxiety and depression.”

Play makes our children smarter

Another leader in the dialogue on active play is researcher and psychiatrist Stuart Brown. In his book, Play: How it Shapes the Brain, Opens the Imagination, and Invigorates the Soul, Brown says that play “fosters empathy and makes possible complex social groups. For us, play lies at the core of creativity and innovation.” First observing animal play in the wild, Brown concluded it is necessary for survival because play “makes animals smarter and more adaptable.”

Other studies support this theory, pointing out that children learn best when stimulated through active play. (There is evidence that free play promotes growth of the cerebral cortex.*) This learning extends to academic settings.

A hallmark of successful schooling, Finland has drawn attention from educators around the world who are trying to understand why the country’s children consistently place near the top in international rankings. Finnish children enter school later than North Americans, spend less time in the classroom, and have more recess or breaks (15 minutes for every 45-minute class attended). In Finland, it appears, more free time, not less, is responsible for academic success.

Play is easier

Many things prevent our children from experiencing optimal amounts of free time, but nothing more than our modern-day parenting style, says Alison Gopnik, professor of psychology at the University of California, Berkeley. In her new book, The Gardener and the Carpenter, Gopnik explores the results of a parenting philosophy that treats children as a product that must be managed and shaped into a positive outcome. The result? Too much interference in children’s lives. Says Gopnik, “The rise of parenting has accompanied the decline of the street, the public playground, the neighborhood, even recess.”

Like Gray and Brown, Gopnik sees the negative implications of this decline in free time. These include guilt and anxiety for parents along with “an oppressive cloud of hovering expectations” for children. Adults can change the outcome for their kids by backing off, lightening up, and letting children experience the messiness and exuberance that is childhood. They can also play themselves, by treating their children like a garden (you never know what you’re going to get when you plant the original seed—but you plant it all the same).

Smarter, happier, well-developed kids

What these scientists have in common is their belief that free and active play is an essential ingredient in a developmentally normal childhood. As the dog days of summer transition into the frenetic days of the school year, parents might consider looking at these results and their own experiences. Before enrolling your child in another structured activity, remember to make time for play.

*Dr. Gwen Dewar, PH.D, Intelligence in Children: Can We Make Our Kids Smarter? Parenting Science.