The decision processes of 6- and 12-person mock juries assigned unanimous and two-thirds majority rules.

720 college students served on 6- or 12-member "juries" that listened to a simulated trial of a rape case, deliberated, and then rendered verdicts according to the unanimity or two-thirds majority social decision rule assigned. Although neither assigned rule nor jury size had a significant effect upon the verdict distribution, average deliberation time and the number of polls were both significantly influenced. Individuals gave a significantly higher proportion of guilty verdicts than did juries. A two-thirds majority social decision scheme model best predicted overall verdict distributions, while a number of other social process models could be confidently rejected. Several other findings are discussed along with the argument for the need for both theoretical and empirical research on juries.