Many decisions lead to consequences for others. Our laboratory explores several sorts of social decisions: those that involve personal sacrifice for another’s benefit (e.g., choices in a competitive game). We adopt the working hypothesis that, throughout evolutionary time, many of the most critical decisions were social, not economic. Thus, neural systems for the adaptive control of behavior often acted to achieve social goals, in concert with systems for understanding the cognitions and desires of others. We believe that this is an important and understudied area of research — one that will merge with neuroeconomics over the coming years.