An experimental study of jury decision rules

We present experimental results on groups facing a decision problem analogo us to that faced by a jury. We consider three treatment variables: group si ze (three or six), number of votes needed for conviction (majority or unani mity), and pre-vote deliberation. We find evidence of strategic voting unde r the unanimity rule: A large fraction of our subjects vote for a decision analogous to conviction even when their private information indicates a sta te analogous to innocence. This is roughly consistent with the game theoret ic predictions of Feddersen and Pesendorfer. Although individual behavior i s explained well by the game theoretic model, there are discrepancies at th e level of the group decision. Contrary to Feddersen and Pesendorfer, in ou r experiments there are fewer outcomes analogous to incorrect convictions u nder unanimity rule than under majority rule. rn the case of no deliberatio n, we simultaneously account for the individual and group data using quanta l response equilibrium.