F rom the perspective of many economists, motives other than self-interest are peripheral to the main thrust of human endeavor, and we indulge them at our peril. In Gordon Tullock's (1976) words (as quoted by Mansbridge, 1990, p. 12), "the average human being is about 95 percent selfish in the narrow sense of the term."In this paper we investigate whether exposure to the self-interest model commonly used in economics alters the extent to which people behave in self-interested ways. The paper is organized into two parts. In the first, we report the results of several empirical studies-some our own, some by others -that suggest economists behave in more self-interested ways. By itself, this evidence does not demonstrate that exposure to the self-interest model causes more self-interested behavior, since it may be that economists were simply more self-interested to begin with, and this difference was one reason they chose to study economics. In the second part of the paper, we present preliminary evidence that exposure to the self-interest model does in fact encourage self-interested behavior.

Studies of reward learning have implicated the striatum as part of a neural circuit that guides and adjusts future behavior on the basis of reward feedback. Here we investigate whether prior social and moral information about potential trading partners affects this neural circuitry. Participants made risky choices about whether to trust hypothetical trading partners after having read vivid descriptions of life events indicating praiseworthy, neutral or suspect moral character. Despite equivalent reinforcement rates for all partners, participants were persistently more likely to make risky choices with the 'good' partner. As expected from previous studies, activation of the caudate nucleus differentiated between positive and negative feedback, but only for the 'neutral' partner. Notably, it did not do so for the 'good' partner and did so only weakly for the 'bad' partner, suggesting that prior social and moral perceptions can diminish reliance on feedback mechanisms in the neural circuitry of trial-and-error reward learning.

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Prevailing economic models of consumer behavior completely ignore the welldocumented link between context and evaluation. We propose and test a theory that explicitly incorporates this link. Changes in one group's spending shift the frame of reference that defines consumption standards for others just below them on the income scale, giving rise to expenditure cascades. Our model, a descendant of James Duesenberry's relative income hypothesis, predicts the observed ways in which individual savings rates respond to changes in both own and others' permanent income, as well as numerous other stylized fact patterns that are difficult to reconcile with prevailing models. Evaluative judgments are known to depend heavily on context. For example, the same car that would have been experienced by most drivers as having brisk acceleration in 1950 would seem sluggish to most drivers today. Similarly, a house of given size is more likely to be viewed as adequate the larger it is relative to other houses in the same local environment. And an effective interview suit is simply one that compares favorably with those worn by other applicants for the same job.