It has long been known that human cooperation is so successful in large part because of our reciprocity. We help those who are likely to help us, and we withhold generosity from people whom we expect to be selfish.
In [a] new study, researchers introduced a behavioral rule that has not been previously explored, the so-called “arbitration tit-for-tat.” If [two partners participating in a version of evolutionary game theory] disagreed on what actions have occurred in the past, they had an option of paying a cost to consult a third-party arbiter. This third-party observer then used their own perspective to align players’ beliefs about what has transpired.
[Evolutionary anthropologists Sarah] Mathew and [Robert] Boyd found that “arbitration tit-for-tat” outperformed other common behavioral rules and restored high cooperation rates even when disagreements were frequent. What’s more, this new strategy fared better than the rival rules even when arbitration itself was not objective.
These new findings help explain why cooperation based on reciprocity is found in humans but not in other animals. Because the threat of retaliatory defection alone is not enough to sustain generosity when facts are disputed, partners in human societies often have to resolve their disagreements by raising the issue with friends, elders, or courts.