1. Department of Psychology and Center for the Study of Brain, Mind, and Behavior, Princeton University, Princeton, NJ 08544, USA.
2. Department of Economics, Harvard University, and National Bureau of Economic Research, Cambridge, MA 02138, USA.
3. Department of Social and Decision Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
4. Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15260, USA.