At least that's what Jonah Lehrer says, discussing a forthcoming paper in Psychological Science about how a jaunt through the great outdoors can actually have significant cognitive benefits:
In particular, being in natural settings restores our ability to exercise directed attention and working memory, which are crucial mental talents. The basic idea is that nature, unlike a city, is filled with inherently interesting stimuli (like a sunset, or an unusual bird) that trigger our involuntary attention, but in a modest fashion. Because you can't help but stop and notice the reddish orange twilight sky—paying attention to the sunset doesn't take any extra work or cognitive control—our attentional circuits are able to refresh themselves. A walk in the woods is like a vacation for the prefrontal cortex.
Strolling in a city, however, forces the brain to constantly remain vigilant, as we avoid obstacles (moving cars), ignore irrelevant stimuli (that puppy in the window) and try not to get lost. The end result is that city walks are less restorative (at least for the prefrontal cortex) than strolls amid the serenity of nature.
In a very similar vein, there was a epidemiological study published in Lancet last Friday that found that living near parks, playing fields, or forests can have dramatic effects on your health—both by alleviating stress and by allowing more physical activity. The researchers went on to suggest that it might be possible to narrow the health gap between the rich and poor by creating more green space in urban areas. (Hey, maybe this even helps explains that recent finding about how Republicans tend to be much healthier than Democrats, seeing as how the latter are more likely to live in cities and have less green space, no? Eh, okay, there are probably better explanations...)