BERKELEY, Calif./DURHAM, N.C. — A great strength of economics is its ability to examine how decisions are made from the point of view of decision makers. For example, economics can explain in this way why consumers buy what they do. It also offers a perspective on why employees work for some employers and not others, why they work as hard as they do, and, indeed, why they go to work at all.

But in most economic analysis, the decision-makers' point of view is quite narrow. It starts with what people like and don't like. People may have a taste for oranges or bananas, or a preference for enjoying life today instead of saving for the future. They then decide what to buy or how much to save, given prevailing prices, interest rates and their own income. Economists have included in such analysis that people interact with others, but they have largely treated such social interactions in a mechanical fashion, as if they were commodities.

For example, in the standard economic analysis of workplace gender discrimination, men do not like to associate with women on the job — in the same way that they might prefer apples to oranges. Likewise, the standard economic analysis of racial discrimination is that whites do not want to associate with nonwhites, and so demand a premium to buy from or work with nonwhites.