Replication Data for: Do Justices Defend the Speech They Hate? An Analysis of In-Group Bias on the U.S. Supreme Court

For decades now, experiments have revealed that we humans tend to evaluate the views or activities of our own group and its members more favorably than outsiders. To assess convergence between experimental and observational results, we explore whether Supreme Court justices fall prey to ingroup bias in freedom of expression cases. A two-level hierarchical model of all votes cast between the 1953 and 2014 terms confirms that they do. Although liberal justices are (overall) more supportive of free speech claims than conservative justices, the votes of both liberal and conservative justices tend to reflect their preferences toward the speech’s ideological grouping, and not solely an underlying taste for (or against) greater protection for expression. These results suggest the importance of new research programs aimed at evaluating how other cognitive biases identified inexperimental work may influence judicial behavior in actual court decisions.