Sunshine spills in through the windows on opposite sides of the upstairs room.

The boys are charging about, letting off steam. Two girls are laying out a tea-party for favourite toys while others are getting to grips with the up-turned buckets that will clang and clatter into service as mini-stilts. And no, it’s not a creche for energetic tots. This is the Chiswick HQ of Rambert Dance Company and an early run-through of director Mark Baldwin’s latest choreography, Seven for a secret, never to be told.

Set to a specially commissioned orchestration, by composer Stephen McNeff, of Ravel’s opera L’enfant et les Sortileges, this is a dance piece focused on child’s play. And Baldwin reckons that it’s been one of his toughest, but equally one of his most intriguing, challenges to date. He knew that the Rambert dancers would pull out all the energy stops if they were asked to act their shoe-sizes rather than their ages, but Baldwin didn’t want some superficial capers in the style of seven-year-olds. He wanted movement – and performances – that engaged on deeper levels with what it means to be seven; to be seeing the world with a child’s eyes, a child’s curiosity, a child’s imagination. And for the running and jumping, the skipping and whirling, to be a true reflection of the wonderment and fresh responses that adults can’t help but lose as they grow up.

In this, he was encouraged and abetted by Rambert’s “scientist-in-residence”, Professor Nicky Clayton. Baldwin had already drawn on her expertise in an earlier collaboration that referenced Darwinian theories, The Comedy of Change (2009). Now he was quizzing her about her specialist knowledge of the behavioural development of children.

“Nicky told us just how important the role of play was in helping children’s brains to learn,” says Baldwin. “She gave us these examples of other species – chimpanzees, but also birds like ravens and magpies – where it looks like the young are just having some fun playing games but actually they’re discovering how to problem-solve. How to survive, really.”

Subsequent conversations expanded everyone’s understanding of the thought processes that condition a child’s way of seeing the world. Baldwin laughs. “Nicky kept reminding us that a child really isn’t a miniature adult. But they don’t necessarily realise that either. They think that whatever they see or do, we are on the same wavelength and that our world and their world are exactly the same – and at a certain stage, the world is them. And I think you can see that every day in supermarkets, can’t you? It takes time for a child to see the world as adults do – and again, part of that development comes about through play; through games that imitate adult behaviour, like playing house or organising make-believe adventures.”

Clayton’s input was soon backed up by sessions of practical observation. Baldwin himself spent hours observing his seven-year-old godson and getting caught up in his full-on hectic games. “He only knows two speeds: flat out and stop. And I’m wondering how to get this quality, this intense physicality, into the choreography without it seeming like some adults imitating what they think children are about.”

So while he headed into the studio – where he spent hours “skipping: happy skipping, bad-tempered skipping, girly skipping …” – some of the dancers sat in on play-groups, trying to get a handle on how youngsters interact with each other when making up their own games.

For Dane Hurst and Eryck Brahmania, both of whom have intensely exuberant solos in Seven for a secret …, these visits tuned them in to the sudden switches in energy levels that see little lads tearing around like heat-seeking missiles one moment before collapsing in a dead heap the next – until the next spurt of stamina sends them rocketing about with renewed gusto. It was the start of a hugely demanding learning curve. Unlike some choreographies where an emotion or an intellectual concept can be taken as a motivating factor, the movement that Baldwin wanted them to capture in this new work seemed driven purely by the impulses of spontaneous child’s play. The secret would be to reconnect with their inner seven-year-old.

“We do like to feel, as adults, that we haven’t entirely lost our ‘inner child’, that we can tap into that wonderment, that carefree spirit,” says Baldwin. “And we can be very sentimental about it. But the more I thought about what Nicky had said about play being good for children, the more I felt that play can be good for all of us. It’s about creativity; about freeing up your mind, playing around with ideas until you come up with something that fires your imagination and, hopefully, if you’re a choreographer, engages other people’s imaginations too. And I suppose, on a much much deeper level, that’s why this piece seemed an appropriate way to mark the 85th anniversary of the company and to acknowledge the innovations of Marie Rambert herself.” The lady was, in fact, known for her playful ability to turn perfect cartwheels.

Perhaps the naughty boy in Ravel’s opera had a similar joie de vivre – when he wasn’t trashing his toys or tormenting small furry critters that is. In Seven for a secret ... the original narrative has, like the singing, been discarded in favour of a new orchestral score that underpins episodes of pillow-fighting, make-believe and chumminess, all garbed in 1950s costuming that hints of a childhood emerging from the dark days of wartime into a supposedly brave new world. “Stephen McNeff has cleverly created a non-vocal homage to the Ravel,” says Baldwin. “Without the singing, you can really hear the rhythms, the tunes, that remind you that Ravel used to write music for a friend’s children. And it just has such charm, and maybe a kind of innocence that we all like to think we had in childhood when the sun shone and we were outdoors with our playmates – all aged seven, and counting magpies.”

Rambert Dance perform Seven for a secret ... as part of a triple bill at Glasgow’s Theatre Royal tonight until Saturday, November 5.