Chimps play fair in the ultimatum game
How do people respond when treated unfairly? Quite often they retaliate, even if it costs them to do so and they end up worse off (in the econ-rational/sociopathic sense). So the rule they follow is not a rule that approximates economic rationality — in fact, it may be better than rational (but it can also cause a lot of trouble).
In fact, this rule is so built-in that it has been found that chimps know that other chimps have this rule built in !!! The rule is basically — if you get treated unfairly, punish whoever did it if you can. This has been embedded in codes of honor for thousands of years.
The ultimatum game (UG) shows this. Behavioral game theorists have tested this game on humans hundreds of times. It goes like this.
- Player A (the proposer) is given $10
- Player A gives B (the responder) some amount, say $3.
- Player B can see that player A had $10 and gave only $3, and must now make one of two moves:
- Accept — in which case A keeps $7 and B keeps $3.
- Reject — in which case both lose everything.
Econ utility theory predicts that Player B will never reject as long as she gets at least $0.01. In reality, people tend to reject if they get less than about $3.00.
The proposer knows that the other person will likely apply a code-of-honor rule if she is too unfair. And a human proposer knows this even though she has not met the other person (as shown in the experiments). So proposers automatically know that the other player will not follow standard economic theory.
Chimp proposers act the same way, but they know the other chimp. Still, they knew how the other chimp would react even though they had never seen any chimp reject in a UG. They just knew “If I’m nasty the other guy will retaliate.”
This has been tested by playing the game but not letting the other retaliate. In this case, the proposers are less generous. You can read the original paper here.
The Importance for Climate Cooperation
People are mostly not sociopaths as standard economics assumes. And most are not terribly altruistic (and countries are even less altruistic). But most people, do tend to retaliate against unfair play. This can get out of hand, but if well managed it can be the key ingredient that holds a cooperative climate agreement together.