Table 1.
Games, actions, and payoffs (Studies 1 and 2).
| Effect on |
|||||||
|---|---|---|---|---|---|---|---|
| Ingroup member |
Outgroup member |
||||||
| Game | Action | 1 (self) | 2 | 3 | 1 | 2 | 3 |
| IPD |
Keep | +€40 | 0 | 0 | 0 | 0 | 0 |
| Between group pool | +€20 | +€20 | +€20 | −€20 | −€20 | −€20 | |
| IPD-MD (original) |
Keep | +€40 | 0 | 0 | 0 | 0 | 0 |
| Between group pool | +€20 | +€20 | +€20 | −€20 | −€20 | −€20 | |
| Within group pool | +€20 | +€20 | +€20 | 0 | 0 | 0 | |
| IPD-MD (positive) | Keep | +€40 | 0 | 0 | 0 | 0 | 0 |
| Between group pool | +€20 | +€20 | +€20 | +€20 | +€20 | +€20 | |
| Within group pool | +€20 | +€20 | +€20 | 0 | 0 | 0 | |
Note: The table illustrates the effect an individual's action has on her own payoff, the payoff of each of two other ingroup members, and that of the three outgroup members. Each player's final payoff is determined by the combined effect of the six (three ingroup + three outgroup) players' actions.