Looking at trees and clouds can ease stress and boost cognitive function, says Dr Eva Selhub, 
co-author of Your Brain on Nature (R216, Kalahari). In a landmark study, researchers at 
the University of Michigan found that people performed better on cognitive tests after hiking in a park than they did after walking through a city. In fact, just gazing at pictures of nature led to a spike in attention. Don’t have a window in your office? Selhub recommends hanging familiar outdoor scenes on your walls. “The natural images turn off the stress response,” she says. “And because it’s personal, you respond almost as if you’re there.”