Research from Finland suggesting that young children need outdoor space to achieve optimum brain development has led to calls for changes in the regulation of private nurseries in Scotland.
Matti Bergstrom, emeritus professor of neurophysiology at Helsinki University, argues that too much order in a child's life can inhibit their learning.
Until the age of six or seven, children must have access to space and freedom to play out their fantasies, Professor Bergstrom says. The area of the brain that processes logic and order has not fully developed and the child depends more on their inner feelings.
However, a study of the regulations relating to outdoor space in children's services, carried out by Children in Europe, has shown that many countries have no requirement or recommendation that would ensure that every child attending an early years service would have access to the outdoor space they need.
In Scotland, requirements for nurseries based in schools state that every child should have access to at least 9.3 square metres of outdoor space.
Pre-school services outwith schools, including private nurseries, are not covered by such regulation.
One of Scotland's leading children's charities, Children in Scotland, has called on the Scottish Executive to extend these regulations to include nurseries outwith the state sector. Bronwen Cohen, its chief executive, said: "The expansion in services for young children means that they are spending more time in organised childcare of some kind. We are also witnessing a decline in access to safe public space, such as town squares or open countryside.
"With less freedom to roam and more time spent in organised space, it is vitally important that we ensure children have access to the outdoors and the opportunity for freedom to explore. Nature can provide the best environment for a child's play.
"It is a worrying trend that there are now fewer requirements for outdoor space in the UK than previously. There is an opportunity for Scotland to improve provision for young children nationwide by extending regulations that already exist for those attending nurseries based in schools."
Professor Bergstrom said: "Spaces that have four walls like the classrooms in many of our schools are not what is required. Why do children seek out the untidy or incomplete, ruined buildings or building sites?
"Buildings which offer young children the chance to reorder, complete or knock down like sandcastles on a beach provide their brains with room to grow and mature.
"The freedom and space that nature offers can provide inspiration for designing indoor spaces too. When we observe children's behaviour in this natural environment, we can see them observing every small detail and absorbing everything around them.
"In nature they find a reflection of their own world."