- [[David Rand|Dave]], [[collective action problem]] # Idea [[Martin Nowak]] discussed such strategies in his book super cooperators. In the [[prisoner's dilemma]] game, the benefits to other(s), $b$ is greater than the cost of cooperation, $c$: $b > c$ ## Repetition and direct reciprocity After a few rounds, people will learn to cooperate because they expect to be reciprocated in the future. People in smaller cities/towns are nicer and cooperative because they know they likely to meet others again, so they expect to be reciprocated. - deviate: 0 - cooperate: $-c + pb$, where $p$ is probability we meet again - $pb$: probability of me benefiting from cooperating with others - $-c + pb > 0$ - thus, if $p > c/b$, we should cooperate I hope to benefit **directly** in the future from a person whom I've helped now. ## Reputation and indirect reciprocity By cooperating, our reputation gets known. We simply replace probability of meeting with probability of reputation being known. I hope that, by helping person A, this person will tell others I'm great, and then other people will do stuff that benefits me in the future. **Denser connections are better**. ## Network reciprocity Let $k$ be the number of neighbors in a [[regular graph]]. If $k < b/c$, we cooperate. **Denser connections are worse.** The denser the connections are between people, the more likely people are to change and defect. ## Group selection Within group, defectors do better. Between groups, groups that have more cooperators are better off than groups with fewer cooperators. ## Kin selection People are related and you can care about other people based on their relatedness, $r$ ([[kin selection]]): $rb > c$ ## Laws and prohibitions Regulate/punish behavior. ## Incentives Regulate/reinforce/reward behavior. # References - https://www.coursera.org/learn/model-thinking/lecture/Oj51H/seven-ways-to-cooperation - [[Nowak 2011 super cooperators]]