According to most economics textbooks, human beings are super-rational creatures who know what is in their own best interests and always act accordingly. When making a decision to buy something, the rational consumer will evaluate all the possible alternatives before making a purchase, having already conducted research on the state of the market. They would not buy something on the spur of the moment, or on the recommendation of a friend. Nor would a rational consumer be unduly influenced by advertising or a brand name in making purchasing decisions. This explanation of human behaviour is known as the rational agent model. Sound realistic?
While the rational agent model is useful for some economic analysis, such as when we examine the economy as a whole, it clearly does not correspond to how human beings behave in the real world. Traditional (or neoclassical) economics, which relies on this model, simply cannot explain why people sometimes make decisions that are not strictly in their own best interests.