Unanimous decision making on the U.S. Supreme Court: Case stimuli and judicial attitudes

Although behavioral scholars have devoted much time and energy to attempting to explain decision making on the U.S. Supreme Court, they have virtually ignored the unanimous decision. We investigated the Vinson, Warren, and Burger Courts and discovered that the liberal outcome was more successful in the unanimous cases whether those cases involve civil liberties or economic liberalism and whether they were decisions to reverse or decisions to affirm. We also ascertained that the ideological position that tended to win in the unanimous reverse cases was related to the ideological position that tended to win in the nonunanimous reverse cases, but that no such relationship was present in the two kinds of affirm cases. These two findings are in conformity with a psychometric model, which posits that the relative position of judicial attitudes and case stimuli determines the vote on the U.S. Supreme Court.