Variation and the response to variation as a basis for successful cooperation

Abstract

In applying game theory to problems in biology, differences between individuals are often ignored. In particular, when analysing the evolution of cooperation it is often implicitly assumed that ignoring variation will produce predictions that approximate the solution when differences are included. This need not be true. As we demonstrate, differences are not innocuous noise, but can fundamentally change the nature of a game. Even small amounts of variability can stabilize cooperation by, for example, maintaining the need to deal with cheaters. Differences promote the need to learn about others in an interaction, leading to contingent behaviour that can reduce conflict, and to negotiated outcomes that may or may not be more cooperative than unconditional actions. Once there are mechanisms such as mutation and environmental influences that maintain variation within populations, whether cooperation evolves may depend on the variation in the cooperativeness trait. Variation means that it may be worth taking a chance that a partner is cooperative by being cooperative. When there are markets, so that individuals can break off interactions to seek a better partner, variation promotes choosiness and hence penalizes those uncooperative individuals, who are rejected. Variation promotes the need to monitor the previous behaviour of others, and once this social sensitivity exists, the need to maintain a good reputation can promote cooperation.

Partner choice versus punishment in human Prisoner’s Dilemmas

“…[1-3] but see [10,22,23]). Incorporating such variation is crucial for understanding how partner choice mechanisms evolve [11]. Studies that have disentangled willingness from ability to give have suggested that willingness might often trump 160 ability to give when evaluating partners [10,22,23].…”

“…Here, we empirically explored how human subjects trade off ability versus willingness to cooperate when choosing a social partner; and whether these preferences are moderated by quality stability (see [11]). 'Choosers' observed the decisions made by two 'dictators' in a modified Dictator Game [12] and then chose which of these individuals they wanted to interact with in a second Dictator 40…”

Cooperation in wild Barbary macaques: factors affecting free partner choice

“…Individuals may be less willing to cooperate with higher ranking partners, which often monopolise experimental apparatuses that dispense food (Chalmeau and Gallo 1993;de Waal and Davis 2003;Drea and Carter 2009;Suchak et al 2014). The temperament of the subjects may also affect cooperation (Bergmüller et al 2010;McNamara and Leimar 2010). In rooks, bolder birds were more willing to approach the experimental apparatus than shier birds, and subjects performed better in a cooperative task when paired with a bolder than shier partner (Scheid and Noë 2010).…”

Culture and cooperation

“…Such inter-individual differences have a potential of explaining aggregate behaviour and group-level differences (e.g. Gächter & Thöni 2005;Kurzban & Houser 2005;Gunnthorsdottir et al 2007;Fischbacher & Gächter 2010) and may play a major role for the stability of cooperation (McNamara & Leimar 2010). …”