The scientific study of the United States Supreme Court had its genesis in the legal realism of the 1920s and 1930s. It flowered with the onset of the behavioral revolution in political science during the 1950s. Both the legal realists and the behavioralists championed the empirical, scientific study of decision making. But most legal realists were also legal reformers, who criticized the conservative appellate court bench of their day by arguing that these judges were not deciding cases on the basis of law, but rather used legal arguments only to support their conservative values. The legal realists favored liberal values.

Since the 1950s almost all behavioral scholars who have attempted to explain decision making on the United States Supreme Court have investigated extralegal variables: the attitudes and ideologies of the justices, the fact patterns of the cases in various issues areas, the justices' social background characteristics, their role perceptions, small group variables, game theoretic strategies, and the influence of interest groups, public opinion, Congress, and the solicitor general. But despite the skepticism of the legal realists and that of the modern critical legal studies movement, it is possible that legal variables also influence the justices' votes.

In this book we will partly test whether legal variables are influential. More specifically, we will test whether stare decisis, one of the elements of the legal model of decision making, influences the justices' votes in cases that alter precedent. We will also test whether the attitudinal model, a model antithetical to the legal model, explains the votes. The analyses regarding the testing of these two models are located in Chapters 6, 7, and 8.