“In common language a rational person is certainly reasonable,” and “generally in tune with reality,” writes Kahneman. But economists generally use rational to mean “logical coherence—reasonable or not.” For example, Becker in “A Rational Theory of Addiction,” says rational means having “a consistent plan to maximize utility over time.” Utility is a theoretical equivalent for profit or pleasure (see Bentham’s bucket error). Becker and his so called rational-agent school, by focusing exclusively on utility, tune out key realities. For them drug addiction is just another method of maximizing utility. Kahneman says Becker’s “faith in human rationality” is ill founded because abundant evidence shows that certain kinds of inconsistency are “built into the design of our minds.” Measuring these “cognitive biases” established the new field of “behavioral economics”—its name amusingly emphasizing what’s been lacking—dedicated to describing the everywhere evident ways in which we often aren’t rational. To minimize misuse, consider that the word rational really incorporates three types of assumptions: first, about desirable goals; second, about effective methods of attaining them; and third, about whether agents have the needed skills. - blogs.scientificamerican.com