Thoreau would have liked this study: interacting with nature (at least when compared to a hectic urban landscape) dramatically improves cognitive function. 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.
My prefrontal cortex and I agree.