The change in children's play habits has emerged over a single generation, helped by two side effects of contemporary culture.
First, the growth of technological (and entirely indoor) screen-based activities has provided a seductive alternative. Second, a huge increase in parental anxiety has led to restrictions on children's physical activity and their freedom to play outdoors. Part of this anxiety is rational - for instance, a huge increase in traffic means the outdoors is less safe every year, and with more parents out at work there are fewer "eyes on the street" to watch out for children's welfare . But part of it is irrational, and itself a consequence of our multimedia culture.
The fact that we can now view (and repeatedly re-view) distressing images of terrible events as if they are happening in front of us has a much greater effect on mental stability than hearing or reading about them.
Neuroscientists have found that horrific pictures directly affect the emotional centres in the brain and the more frequently they're viewed, the more they induce anxiety. Psychologists researching the World Trade Center attack on the American public found that the more TV people watched, the more likely they were to suffer psychological effects.
TV coverage of horrific news, such as the Soham murders of 2002, forces parents to confront their own worst fears over and over again. The fact that this coverage continues remorselessly, 247, in the corner of one's own living room, makes it even more powerful. So, even though we know that the dangers of child abduction are no greater today than they were 50 years ago, media-induced anxiety overcomes reasoned argument.
Baroness Greenfield has made us aware that technological culture may be changing children's brains, but it's also changing adults' brains: it's making all of us irrationally over-protective.
Research at Lancaster university has found that, compared even to the 1990s, today's 10 and 11-year-olds are given a smaller and more clearly specified area in which they can play freely, are monitored much more closely by their parents, and have their play curtailed at the first hint of danger. Younger children often scarcely venture out at all, but remain cooped up like battery chickens with their technological toys for company, perhaps the most inactive generation in human history.
If we're to reinstate real play, adults must overcome this generalised fear, work together to make the great outdoors as safe as possible, and give our children the freedom to go out to play.