 Several decision rules with this structure have been proposed. One of the earliest was Handa (1977). Currently, the best known proposal in this tradition is prospect theory (Kahneman and Tversky 1979; Tversky and Kahneman 1986), which was developed in order to describe observations from psychological decision experiments more accurately than in expected utility theory. Prospect theory a is a fairly complex theory that also deviates in other ways from expected utility theory. The traditional focus on outcomes is replaced by a focus on losses and gains, which are treated asymmetrically. (See also Section 7.3.)