Judges indeed play a central role in the American legal system— more so than in most others. But the behavior of American judges, and in particular the determinants of their decisions, are not well understood, including by lawyers, law professors, and even many judges (we’ll explain that paradox in due course). In part this is because judges in our system are permitted to be, and most are, quite secretive.2 Indirect methods must be employed to understand their behavior. Beginning more than half a century ago but accelerating in recent scientists in particular, but also economists and psychologists, and, increasingly, academic lawyers knowledgeable about social science—have used ever more sophisticated theoretical concepts and quantitative tools to penetrate self-serving judicial rhetoric,