Judges like to claim that they are impartial decision-makers fully capable of suppressing their personal proclivities, as the rule of law requires. But a century’s worth of studies undermines that view. Going under the name ‘judicial behaviour’, this vast literature shows that many extraneous (non-legal) factors affect the choices judges make. This article focuses on one strand of that literature – the effect of personal characteristics on judging, with emphasis on social identity and social diversity. We show that the literature is bifurcated: studies focusing on the social identity of individual judges (such as their gender, race, and nationality) generate findings consistent with in-group bias, whereas research on the social diversity of judges sitting in panels suggests that benefits can accrue from socially diverse courts. What the two sets of studies have in common, though, is just as important: both could make profound academic and policy contributions but require far more development if they are to realize their potential. We offer proposals for forward movement.
