Significantly, strong reciprocators will behave this way even if doing so provides no prospect of material rewards in the future.

ECONOMIST: Human behaviour

And the three strategies did, indeed, have the same average pay-offs to the individuals who played them though only 13% were co-operators, 20% free-riders and 63% reciprocators.

ECONOMIST: Human evolution

The researchers were able to divide their subjects very cleanly into co-operators, free-riders and reciprocators, based on how many tokens they contributed to the pool, and how they reacted to the collective contributions of others.

ECONOMIST: Human evolution