Cooperation as a successful strategy has evolved both in nature and in human society, but understanding its emergence can be a difficult task. Researchers need to summarize the interactions between individuals in mathematical formulas so that they can create a model that can be used for predictions and simulations.
In the field of evolutionary game theory, they often study the strategies of players in a simple game of giving and receiving profit. Such strategies tell players how to behave in a given interaction. Scientists’ findings counter the narrative that only the strongest and most selfish thrive and survive. Instead, they show how cooperation can be an effective and stable strategy.
The researchers, led by Laura Schmid of the Chatterjee group at IST Austria, have created a new mathematical framework that combines hitherto incompatible descriptions of cooperation. In their simulations of many interactions between players, they show how past experiences and the reputation of a potential partner affect players’ willingness to cooperate with them.
Scratched back and flawless reputation
The central concept of the researchers’ work is that of interactions based on direct and indirect reciprocity. “An interaction based on direct reciprocity just means ‘I’ll scratch your back if you scratch mine,'” says Laura Schmid, “It can be found both in humans and in several animal species.”
In contrast, indirect reciprocity is based on an individual’s reputation. “This means that if they behave well towards others, I will cooperate with them, even if I have never interacted with that individual before,” continues Schmid. “So far, this has only been conclusively shown among humans.”
Resolving the conflicts that arise when these two types of reciprocity lead to competing suggestions is not straightforward. Should the player cooperate with someone 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.
One of the key insights the researchers gleaned from their unified model of direct and indirect reciprocity was that the evolution of strategies, the level of cooperation, as well as the type of reciprocity that individuals prefer, all depend on the environment. : Factors like how often players interact and whether they know the truth about their partner’s reputation.
This model can help researchers understand the fundamental dynamics of the evolution and stabilization of cooperative strategies. “Using mathematical tools that were only recently developed, we explored which direct or indirect reciprocity strategies give rise to a Nash equilibrium,” Schmid points out. “Once the evolving population of actors in our simulation adopts such strategies, none of them are prompted to turn away.”
These findings shed light on how the development of cooperation in early human societies might have been influenced by their social norms based on experience and reputation. A more common application would be the modeling of online store rating systems based on both the personal experience of the buyer and the reputation of a seller.
Connecting different fields such as game theory and evolutionary modeling has been a topic for Laura Schmid for some time. Growing up in Vienna, she first studied physics at TU Wien as well as piano at the Vienna City University of Music and Arts before joining the Chatterjee group at IST Austria for her doctorate. . After graduating later this year, she plans to pursue her research career abroad.
In her future work, Laura Schmid wants to see how many actors in a group must use a strategy based on indirect reciprocity to be successful. With this, she will be able to study the effect of the diffusion of social norms within a society.