Symposium: Modeling Human Decisionmaking in the Law the Neurobiology of Opinions: Can Judges and Juries Be Impartial?

In this Article we build on neuroscience evidence to model belief formation and study decisionmaking by judges and juries. We show that physiological constraints generate posterior beliefs with properties that are qualitatively different from traditional Bayesian theory. In particular, decisionmakers will tend to reinforce their prior beliefs and to hold posteriors influenced by their preferences. We study the implications of the theory for decisions rendered by judges and juries. We show that early cases in judges’ careers may affect their decisions later on, and that early evidence produced in a trial may matter more than late evidence. In the case of juries, we show that the well-known polarization effect is a direct * Associate Professor of Economics, University of Southern California; Research Fellow, Center for Economic Policy Research. We are grateful to participants in the Center for the Study of Law and Politics symposium on “Modeling Human Decisionmaking in the Law” for useful comments. † Professor of Economics, University of Southern California; Research Fellow, Center for Economic Policy Research. 422 SOUTHERN CALIFORNIA LAW REVIEW [Vol. 86:421 consequence of physiological constraints. It is more likely to be observed when information is mixed, as behavioral evidence suggests, and when prior beliefs and preferences are initially more divergent across jurors.