Saw this article in the New York Times Science section on Tuesday:

http://www.nytimes.com/2014/04/01/science/spite-is-good-spite-works.html?emc=edit_th_20140401&nl=todaysheadlines&nlid=39603747&_r=0

Never knew spite was the subject of scientific research! Informative read, with some interesting insights into human behavior.

Don