This essay provides a perspective on the trend towards integrating psychology into economics. Some topics are discussed, and arguments are provided for why movement towards greater psychological realism in economics will improve mainstream economics.

We develop a model that fleshes out, extends, and modifies existing models of referencedependent preferences and loss aversion while accomodating most of the evidence motivating these models. Our approach makes reference-dependent theory more broadly applicable by avoiding some of the ways that prevailing models—if applied literally and without ancillary assumptions—make variously weak and incorrect predictions. Our model combines the reference-dependent gain-loss utility with standard economic “consumption utility ” and clarifies the relationship between the two. Most importantly, we posit that a person’s reference point is her recent expectations about outcomes (rather than the status quo), and assume that behavior accords to a personal equilibrium: The person maximizes utility given her rational expectations about outcomes, where these expectations depend on her own anticipated behavior. We apply our theory to consumer behavior, and emphasize that a consumer’s willingness to pay for a good is endogenously determined by the market distribution of prices and how she expects to respond to these prices. Because a buyer’s willingness to buy depends on whether she anticipates buying the good, for a range of market prices there are multiple personal equilibria. This multiplicity disappears when the consumer is sufficiently uncertain about the price she will face. Because paying more than she anticipated induces a sense of loss in the buyer, the lower the prices at which she expects to buy the lower will be her willingness to pay. In some situations, a known stochastic decrease in prices can even lower the quantity demanded.

Even though the provision of equal opportunities for men and women has been a priority in many countries, large gender differences prevail in competitive high-ranking positions. Suggested explanations include discrimination and differences in preferences and human capital. In this paper we present experimental evidence in support of an additional factor: women may be less effective than men in competitive environments, even if they are able to perform similarly in noncompetitive environments. In a laboratory experiment we observe, as we increase the competitiveness of the environment, a signi�cant increase in performance for men, but not for women. This results in a signi�cant gender gap in performance in tournaments, while there is no gap when participants are paid according to piece rate. This effect is stronger when women have to compete against men than in single-sex competitive environments: this suggests that women may be able to perform in competitive environments per se. I.

A referenc'8---bcb' generalisation ofsubjecbw8 expecc utility theory is presented. In this theory,preferencb betweenacw depend both on finaloutcD---: and onreferenc points (whic may e uncL':bw acL' It iscD'GPGbwD:FL y a set of axioms in a Savage-style framework. A restricDF form of the theory separates attitudes to end states(encsb8 in a `satisfacF---L funcfacF from attitudes to gains and losses ofsatisfacD---qP Given weak additional assumptions, the restricbw theoryexcrybD ccry ofcb8'---q explains o served disparities etween willingness-to-pay and willingness-to-acbD' valuations of lotteries, and predicD preferenc reversal.

Modern finance has generated a set of formal models of the workings of financial markets that certainly excel in terms of mathematical elegance. But abstract beauty and logical appeal do not guarantee scientific validity. The illustrious late Richard Feynman, professor of physics at Caltech, made the same observation when he discussed the derivation of the law of gravitational potential energy from the "axiom" of conservation of energy. (See the above quote.) Fortunately for physicists, there is ample evidence that the law of gravitational potential energy is correct (to a certain degree). In contrast, there appears to be surprisingly little scientific support for even the most widely used financial model, namely, the CAPM. One can sympathize with E. Fama and K. French when they have recently begun to promote a pricing model that is based entirely on statistical regularities, even if it begs the question why it is more successful. To put this di#erently, asset pricing is paradoxical

Trust management model that we present is adapted for ubiquitous devices cooperation, rather than for classic client-supplier relationship. We use fuzzy numbers to represent trust, to capture both the trust value and its uncertainty. The model contains the trust representation part, decisionmaking part and a learning part. In our representation, we define the trusted agents as a type-2 fuzzy set. In a decisionmaking part, we use the methods from the fuzzy rule computation and fuzzy control domain to take trusting decision. For trust learning, we use a strictly iterative approach, well adapted to constrained environments. We verify our model in a multi-agent simulation where the agents in the community learn to identify defecting members and progressively refuse to cooperate with them. Our simulation contains significant background noise to validate model robustness.

This paper develops a new method of estimating risk aversion using data on labor supply behavior. In particular, I show that existing evidence on labor supply behavior places a tight upper bound on risk aversion in the expected utility model. I derive a formula for the coefficient of relative risk aversion ( ) in terms of (1) the ratio of the income elasticity of labor supply to the wage elasticity and (2) the degree of complementarity between consumption and labor. I bound the degree of complementarity using data on consumption choices when labor supply varies randomly across states. Using labor supply elasticity estimates from thirty-three studies, I find a mean estimate of 1: I then show that generating> 2 would require that wage increases cause sharper reductions in labor supply than estimated in any of the studies.

The debate between “structural” and “reduced-form” approaches has generated substantial controversy in applied economics. This article reviews a recent literature in public economics that combines the advantages of reduced-form strategies –transparent and credible identification – with an important advantage of structural models – the ability to make predictions about counterfactual outcomes and welfare. This literature has developed formulas for the welfare consequences of various policies that are functions of reduced-form elasticities rather than structural primitives. I present a general framework that shows how many policy questions can be answered by estimating a small set of sufficient statistics using program evaluation methods. I use this framework to synthesize the modern literature on taxation, social insurance, and behavioral welfare economics. Finally, I discuss problems in macroeconomics, labor, development, and industrial organization that could be tackled using the sufficient statistic approach.

Studies of risk preference have empirically established two regularities that are inconsistent with the canonical expected utility model: (1) risk aversion over small gambles greatly exceeds risk aversion over larger stakes and (2) insurance buyers play the lottery. This paper characterizes risk preferences both theoretically and empirically in a world with two consumption goods, one of which involvesacommitmentinthatanadjustmentcostmustbepaidwhenthegood is sold. In this model, utility over wealth is more curved locally than globally: individuals are more risk averse with respect to moderate-scale income fluctuations than they are to large income fluctuations. Commitments also create a gambling motive. The empirical importance of commitments is tested using the labor-supply method of estimating risk aversion of Chetty (2003a). Global curvature is imputed using existing labor supply elasticities, and variations in unemployment insurance laws are used to estimate local curvature in a dynamic job search model. Commitments significantly change preferences over wealth: The local coefficient of relative risk aversion is an order of magnitude larger than the global one. Implications for a broad set of questions such as optimal social insurance policies and portfolio choice are discussed.

We argue that “narrow framing, ” whereby an agent who is offered a new gamble evaluates that gamble in isolation, may be a more important feature of decisionmaking than previously realized. Our starting point is the evidence that people are often averse to a small, independent gamble, even when the gamble is actuarially favorable. We find that a surprisingly wide range of utility functions, including many nonexpected utility specifications, have trouble explaining this evidence, but that this difficulty can be overcome by allowing for narrow framing. Our analysis makes predictions as to what kinds of preferences can most easily address the stock market participation puzzle. (JEL D81, G11) Economists, and financial economists in particular, have long been interested in how people evaluate risk. In this paper, we try to shed new light on this topic. Specifically, we argue that a feature known as “narrow framing ” may play a more important role in decision-making under