Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I even say who wrote them. If you have more recent summaries to add to this collection, send them my way I guess. Sorry for the ads; they cover the costs of keeping this online.
Fehr and Fischbacher. 2004. Social norms and human cooperation. TRENDS in Cognitive Sciences 8 (4).
A review. Sanctions are decisive in establishing norms. Tit-for-tat matters; norms are established when people are sanctioned for defecting and rewarded for cooperating.
There seems to be little evidence that punishing is done out of self-interest; even if players rotate (so you don't play the same player more than once), you'll still punish people who defected in previous rounds.
The authors review evidence that shows that a strong norm for human cooperation exists, and that sanctions are decisive for norm formation. These sanctions are largely driven by non selfish motives.
Humans represent an outlier among animal species in that they exhibit large scale cooperation among genetically unrelated individuals. This cooperation is largely based on the norm of conditional cooperation. That is, individuals play a tit for tat strategy, cooperating when others cooperating and defecting when others defect. This holds with 2-person games, and also with 3rd party enforcement games (where the other person's actions don't affect the punisher--supporting norm theory). Punishment is conditional. Results show 50% punished defection in 3rd party games.
The impact of sanctioning on these games has been measured experimentally. Results show that while the interactions provide incentives to defect, the moment a punishment mechanism is introduced into games cooperation increases.
The motives behind sanctioning have not turned up evidence of self-interest, nor have they rejected it:
The evolutionary origin of human cooperation is their conclusion. Since the norm of cooperation is not found in other animals, it must have uniquely evolved in humans. They suggest that even hunter-gatherers were punished if they did not cooperate, making it advantageous to develop altruism.
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