This supplement contains extended formal results for Daley and Sadowski (2015) (henceforth DS15). Specifically, §S.1 establishes that in Prisoners’ Dilemma (PD) games, the model of DS15 is logically distinct from three models that employ well-known forms of other-regarding preferences: altruism (Ledyard, 1995; Levine, 1998), inequity aversion (Fehr and Schmidt, 1999), and reciprocity (Rabin, 19...