Partner choice versus punishment in human Prisoner’s Dilemmas

Abstract

Partner choice is an important force underpinning cooperation in humans and other animals. 10Nevertheless, the mechanisms individuals use to evaluate and discriminate among partners who vary across different dimensions are poorly understood. Generally, individuals are expected to prefer partners who are both able and willing to invest in cooperation but how do individuals prioritise ability over willingness to invest when these characteristics are opposed to one another?We used a modified Dictator Game to tackle this question. Choosers evaluated partners varying in 15 quality (proxied by wealth) and fairness, in conditions when wealth was relatively stable or liable to change. When both partners were equally fair (or unfair), choosers typically preferred the richer partner. Nevertheless, when asked to choose between a rich-stingy or a poor-fair partner, choosers prioritised fairness over wealth -with this preference being particularly pronounced when wealth was unstable. The implications of these findings for real-world partner choice are discussed. 20

How chimpanzees cooperate in a competitive world

“…Overall, our findings contrast sharply with reports of high levels of competition, low levels of tolerance, and harassment-induced food transfers among chimpanzees (38,55). Given that in previous studies chimpanzees did not have a free choice of partners, it may be that partner choice is an essential mechanism that is preferred over punishment to enhance cooperation (23,56). This theory is consistent with evidence that other species prefer withdrawal over punishment as an enforcement mechanism (30), and both theoretical and empirical evidence favoring partner choice over punishment in humans (1,9,(21)(22)(23)56).…”

“…Given that in previous studies chimpanzees did not have a free choice of partners, it may be that partner choice is an essential mechanism that is preferred over punishment to enhance cooperation (23,56). This theory is consistent with evidence that other species prefer withdrawal over punishment as an enforcement mechanism (30), and both theoretical and empirical evidence favoring partner choice over punishment in humans (1,9,(21)(22)(23)56). The chimpanzees' preference for cooperation during this study demonstrates their ability to inhibit competition to increase long-term payoffs.…”

“…Claims of ubiquity and human uniqueness in the use of punishment may have been overstated (9), however, because evidence of these strategies in field and cross-cultural studies of humans has been mixed (18). Punishment in cooperative contexts appears to depend on the scale of the society (19) and the possibility of retribution (20), whereas alternative enforcement mechanisms, such as partner choice, may be equally important for maintaining cooperation (21)(22)(23). In theoretical models, partner choice based on simple reinforcement, choosing the partner who has benefited you in the past, can lead to a cooperative equilibrium faster than if partner choice is not allowed (24).…”

“…Humans show flexible, facultative enforcement strategies adjusted to the context, the intention or motivation of the cheater, the availability of alternative strategies, and the scope of competition (23,31). For example, humans only avoid partners that freeload if those partners cheated intentionally (32).…”

Expectations of Fairness and Trust Co-Evolve in Environments of Partial Information

“…Since costly punishment is known to confer long-term benefits in environments where reputation is built [41,71], a large amount of recent work on partner choice has considered the formation of multiple-round partnerships and the cost of leaving such partnerships [7,26]. It is important to note that the models presented here consider partner choice in a one-shot game.…”