Synthese (2012) 187:293–304 DOI 10.1007/s11229-011-0029-z Decision making and equilibria Aldo Rustichini Received: 30 September 2011 / Accepted: 30 September 2011 / Published online: 14 October 2011 © Springer Science+Business Media B.V. 2011 Abstract In economics and in the social sciences, the study of decision making of the single individual is an important preliminary step to provide a sound foundation for the analysis of equilibria in economic and social systems. Neuroeconomic analysis of the process has been a recent fruitful development in this direction. In the more recent past a new direction of research has emerged, studying the interplay of the decision making of the single individual with the economic and social environment that surrounds him. We review some of the results in this field, both theoretical and experimental, and suggest that a closer development of these two methods of research will be necessary in the future. Keywords Neuroeconomics · Decision theory · Efficient market hypothesis · Market selection hypothesis 1 Preferences and markets: the classical view In the theory of decision making developed by modern economic theory, choices of individuals are the outcome of the optimal selection out of a set of feasible options. Each individual has a ranking over the options, which is his preference order. These order characterize his behavior in several dimensions. For example, they may deter- mine his attitude to saving versus consuming today, or equivalently his preference over payments at different points in time. Or it may determine his attitude to pay- ments subject to uncertainty. The first dimension characterizes his attitude to delayed A. Rustichini (B ) Department of Economics, University of Minnesota, 1925 4th Street South 4-101 Hanson Hall, Minneapolis, MN 55455, USA e-mail: arust@econ.umn.edu 123