Cooperation plays a crucial role in evolution. A team of scientists has now created a new model that shows how different kinds of cooperative strategies among humans develop. Using their unified framework, they show how an individual’s experience and the reputation of others influence the emergence of successful cooperation.

In the field of evolutionary game theory, they often investigate strategies of players in a simple game of giving and receiving benefits. Such strategies tell players how to behave in a given interaction. The scientists’ findings counter the narrative that only the strongest and most selfish flourish and survive. Instead, they show how cooperation can be a successful and stable strategy.

Researchers, spearheaded by Laura Schmid from the Chatterjee group at IST Austria, have created a new mathematical framework that combines so far incompatible descriptions of cooperation. In their simulations of many interactions between players, they show how prior experiences with and reputation of a potential partner affect the willingness of a players to cooperate with them.

Scratched Backs and Flawless Reputation

The central concept in the researchers’ work is that of interactions based on direct and indirect reciprocity. «An interaction based on direct reciprocity simply means ‘I’ll scratch your back if you scratch mine’,» Laura Schmid explains, «It can be found both among humans and several animal species.»

On the other hand, indirect reciprocity is based on the reputation of an individual. «This means that if they behave well towards others, I will cooperate with them, even if I have not interacted with that individual before,» Schmid continues, «So far this has conclusively only been shown among humans.»

Resolving conflicts that arise when these two kinds of reciprocity lead to competing suggestions is not straightforward. Should the player cooperate with a person who behaves well towards others, even if they have treated them unfairly in the past? The strategies adopted by the players then answer this kind of question.

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Materials provided by Institute of Science and Technology Austria. Note: Content may be edited for style and length.