Effects of group decision rules on decisions involving continuous alternatives: The unanimity rule and extreme decisions in mock civil juries

Two experiments examined the effects of majority and unanimity decision rules on group decisions involving continuous alternatives. Each experiment used mock civil juries to test three hypotheses related to the claim that when the distribution of group members’ initial preferences is skewed, the group’s decision will be influenced more by the presence of outlier members under unanimity rule than under majority rule. Experiment 1 tested the hypotheses using a punitive damages case and positively skewed preference distributions. Experiment 2 tested the hypotheses using a compensatory damages case and manipulating the skewness of preference distributions in a 2 (group decision rule) × 2 (valence of skewness) factorial design. In both experiments, the extreme (outlier) member’s individual preference was significantly correlated with the group decision only under unanimity rule. A simple thought experiment based on the experimental results is suggested regarding the implications of using unanimity or majority rule for making decisions in civil juries.