Stake size effects in ultimatum game and dictator game offers: a meta-analysis

Are people more generous when less money is at stake? The Ultimatum Game (UG) and Dictator Game (DG) are often used as models of bargaining and charitable giving, respectively. Previous studies have produced conflicting results on whether UG and DG offers are lower when the stakes are high, and many previous studies had insufficient statistical power to detect significant effects of stake size. To resolve this, we conducted a meta analysis of 31 existing studies that manipulated the size of participants' endowments in the UG and DG (3233 total participants). We hypothesized that: (1) proposer offers would be lower with larger stakes in both games, owing to an increased cost of giving; and (2) offers would decrease more with stake size in the DG than the UG because proposers would not want to risk their offer being rejected in the UG. Our results found almost zero effect of stake size on UG offers (d = 0.02), and a small but significant effect of stake size on DG offers (d = 0.15). Furthermore, larger differences in stakes had little impact on the effect sizes in the UG, but had a medium-large impact on the effect sizes in the DG. These results show that higher stakes reduce donations in the DG, albeit not by much, and have little to no effect in the UG.