Networks

https://www.sciencedirect.com/science/article/pii/S0167268117302159?via%3Dihub

We think a lot of things when it comes to monkeys, phrases like “Monkey see, monkey do,” that they will snatch and screech for bananas or grapes or whatever else they can grasp. It seems as if only humans are capable of altruistic actions; isn’t it human to sacrifice for others? To forgo one’s own needs and wants for another? Turns out, that trait may be an evolutionarily developed. In a research experiment done by Brosnan et al. in 2017, they looked at the decision-making process in chimpanzees, Rhesus monkeys, Capuchin monkeys, and humans. As is in classic economics studies, they used a Hawk-dove game with two asymmetric Nash equilibria. These species were chosen as all four are highly social and cooperate with others over many different contexts. All of these species have evolved some sort of social structure, whether despotic, communal, familial, or something in between. Although causality could not be drawn from the decision making results in the study, it gave insight into how decision making could possibly be selected for as a species evolves.

Depending on cognitive abilities, there were several predicted outcomes. The outcome that was surprising, however, were the results of the capuchin monkeys. It was predicted that “anti-matching,” or picking the opposite choice than the opponent, would not happen as it is a cognitively harder decision to make. Only in cases of anti-matching, would one be able to reach Nash equilibrium in the Hawk-dove game. However, the capuchins were able to reach Nash equilibrium. In all cases of play, they were able to settle on asymmetric equilibrium. However, this only happened when they were able to see the opponent’s decision. In sequential play, the capuchins would choose the option that would lead to equilibrium consistently. However, they could not alternate between equilibria, meaning that they could not reach a mutually beneficial equilibria.
The rhesus monkeys were able to reach Nash equilibrium, but not as consistently. However, they were able to do so without knowing the response of their opponent. By inference, this may be due to the capuchins’ nature of spending most of their time in close proximity, therefore not needing to make decisions alone. Rhesus monkeys form much larger groups, therefore the need for decision making alone may have been selected for. However, in the end only humans were able to reach alternating Nash equilibrium, something that may have separated humans evolutionarily from other primates. We are able to make decisions not only from experience, but in context, in awareness of other’s motivations, and to mutually benefit overall.

Such a simple game of Hawk-dove can reveal a lot about each species’ sociology and hierarchy. In networks, we use learn about how Nash equilibrium is reached and how it exists in real life. However, we can use this tool to also analyze and deconstruct the decision-making of other animals, humans, and entities.