All truly great thoughts are conceived while walking," observed Nietzsche, though I've always been a bit suspicious of the ardour with which writers and artists celebrate the inspirational power of taking a stroll: procrastination is a wily foe, and relishes convincing you that your preferred mode of time-wasting is critical to your success. Yet it seems to work. "Methinks the moment my legs begin to move, my thoughts begin to flow," was how Henry Thoreau described an experience many of us have had, be it tackling challenging work or fretting over problems. For what it's worth, I almost always plan this column in ambulatory fashion, muttering to myself in the park. I lay claim to no "great thoughts", but they'd be far worse without walking. And muttering. (Though I'd prefer not to dwell on that, thanks.)
If we still don't know why walking inspires clarity and creativity, it's because there are too many possible explanations, not too few. An evolutionary psychologist might say we're designed to thrive outside, not at a desk; a scholar of the psychological phenomenon of "priming" might point to studies suggesting that high ceilings – and also, perhaps, the sky – prompt unrestrained thinking. Dreamier types speak of the trance-inducing rhythm of pacing. A study in the European Journal of Developmental Psychology offers more straightforward reasoning. In it, both children and adults performed a memory exercise better when walking than sitting. The researchers speculate that the physiological arousal of walking simply makes for better brain functioning, while the normally detrimental effects of multitasking are eliminated when the tasks are sufficiently different, drawing on separate "wells" of attention, rather than fighting over one.
Maybe. Going solely on anecdotal experience, though, I suspect the greatest mental benefits of walking are explained not by what it is, but by what it isn't. When you go outside, you cease what you're doing, and stopping trying to achieve something is often key to achieving it. (See also: dating, insomnia.) Stepping away from work combats the paralysing effects of perfectionism, because when a task is suspended, the risk of failure is suspended, too; you're thus freer to dream up insights. And in some hard-to-specify way, even the distractions of walking – traffic noise, people – seem to help. The writer Ron Rosenbaum takes this to extremes, not just walking while thinking, but watching TV while writing. "I'm slightly ashamed to admit it, [since] it sounds like such a horrid violation of the writer's solitude," he once said. "But I have a theory of 'competing concentration'… if you have something that you have to focus against... it forces you to concentrate."
Naturally, the self-improvement industry has ideas to optimise your inspirational walking – the Idea Organiser app will capture your breakthroughs (so will a notebook). I'm more sceptical of the merits of a desk for home treadmills, while the aforementioned evolutionary psychologist would probably advise wearing Vibram "foot-gloves" for added authenticity. But all you really need do is go for a walk. "I only went out for a walk and finally concluded to stay out till sundown," the naturalist John Muir wrote, "for going out, I found, was really going in." Deep. Though apparently he never had to worry about deadlines.