Last updated on November 24, 2013
According to Wiki, behavioral economics
stud[ies] the effects of social, cognitive, and emotional factors on the economic decisions of individuals and institutions and the consequences for market prices, returns, and the resource allocation. The field [is] primarily concerned with the bounds of rationality of economic agents.
In case you never took a class on the topic and would like to learn the basics, my friend and coauthor David Just’s Introduction to Behavioral Economics was just published by Wiley. You can buy it here for the relatively low price (for a textbook, that is) of $112.50.