“…We use the computer as the human player's opponent to choose randomly following a fixed probability. Game experiments often use virtual computer players (Brenner & Vriend, 2006;Mccabe, Houser, Ryan, Smith, & Trouard, 2001;Winter & Za-mir, 2005;Houser & Kurzban, 2002;Ferraro, Rondeau, & Poe, 2003;Yamakawa, Okano, & Saijo, 2016;Cox, 2017), which are easy to control. This is a feasible approach because although people may be less altruistic when interacting with the computer than when interacting with a human opponent, the subjects' feedback on how the opponent treats them will not be reduced (Sandoval, Brandstetter, Obaid, & Bartneck, 2016).…”