Dan Ariely is fast becoming the guru in Applied Behavioural Economics. He's one of the first academics, who actually took the knowledge of research to the masses. His books Predictable Irrational and The Upside of Irrationality elegantly describe what people base their decisions on, and why we constantly make suboptimal choices. Its serves as a great starting text for insight into prospect theory and the rational theory of decision making. The following is one of his most popular talks, delivered at TED, California.