maximal element. The preference between two alternatives can be: Strict preference occurs when an individual prefers a1 to a2 and does not view them as equally preferred. Weak preference implies that individual either strictly prefers a1 over a2 or is indifferent between them. Indifference occurs when an individual neither prefers a1 to a2, nor a2 to a1. Since (by completeness) the individual does not refuse a comparison, they must therefore be indifferent in this case. Research that took off in the 1980s sought to develop models that drop these assumptions and argue that such behaviour could still be rational, Anand (1993). This work, often conducted by economic theorists and analytical philosophers, suggests ultimately that the assumptions or axioms above are not completely general and might at best be regarded as approximations. Additional assumptions Perfect information: The simple rational choice model above assumes that the individual has full or perfect information about the alternatives, i.e., the ranking between two alternatives involves no uncertainty. Choice under uncertainty: In a richer model that involves uncertainty about the how choices (actions) lead to eventual outcomes, the individual effectively chooses between lotteries, where each lottery induces a different probability distribution over outcomes. The additional assumption of independence of irrelevant alternatives then leads to expected utility theory. Inter-temporal choice: when decisions affect choices (such as consumption) at different points in time, the standard method for evaluating alternatives across time involves discounting future payoffs. Limited cognitive ability: identifying and weighing each alternative against every other may take time, effort, and mental capacity. Recognising the cost that these impose or cognitive limitations of individuals gives rise to theories of bounded rationality. Alternative theories of human action include such components as Amos Tversky and Daniel Kahneman's prospect theory, which reflects the empirical finding that, contrary to standard preferences assumed under neoclassical economics, individuals attach extra value to items that they already own compared to similar items owned by others. Under standard preferences, the amount that an individual is willing to pay for an item (such as a drinking mug) is assumed to equal the amount they are willing to be paid in order to part with it. In experiments, the latter price is sometimes significantly higher than the former (but see Plott and Zeiler 2005, Plott and Zeiler 2007 and Klass and Zeiler, 2013). Tversky and Kahneman do not characterize loss aversion as irrational. Behavioral economics includes a large