Trees and shade do more than cool people off physically; they also help cool tempers. A University of Illinois study found that levels of aggression and violence were significantly lower among residents who had some nearby nature outside their apartments than among residents who lived in barren conditions. The study also found that inner city families with trees and greenery in their immediate outdoor surroundings have safer domestic environments than families who live in buildings that are barren of nature. According to the study, exposure to trees and greenery reduces mental fatigue and feelings of irritability that come with it. The ability to concentrate is refreshed, along with the ability and willingness to deal with problems thoughtfully and less aggressively. For more about this study, click here.