A. Cooperative responses in 24 trials/day (mean±SEM) from rats playing iterated Prisoner’s Dilemma (IPD) or Stag Hunt (SH) with a Stooge who follows a random response strategy (IPD-Random, closed symbols), Win-stay/Lose-shift (IPD-WSLS, gray symbols), or Tit-for-tat (IPD-TFT, open symbols; SH-TFT, striped symbols). See Figure 1 for experimental details. B. Cooperative responses on the first trial each day (Nice). Cooperative responses vs pellets earned for individual rats playing IPD-Random (C), IPD-WSLS (D), IPD-TFT (E), or SH-TFT (F).