Behavioral Responses to Social Dilemmas

I had the opportunity today to attend a talk by Yamir Moreno, of the University of Zaragoza in Spain. A physicist by training, Moreno has more recently been studying game theory and human behavior, particularly in a complex systems setting.

In research published in 2012, Moreno and his team had people of various age groups play a typical prisoners dilemma game: a common scenario where an individual’s best move is to defect, but everyone suffers if everyone defects. The best outcome is for everyone to cooperate, but that can be hard to achieve since individuals have incentives to defect.

Playing in groups of 4 over several rounds, players were matched by a variable landscape – one group existed on a traditional lattice, while in another incarnation of the game players existed in a scale-free network.

As you might expect from a prisoner’s dilemma, when a person’s neighbors cooperated that person was more likely to cooperate in later rounds. When a person’s neighbors defected, that person was more likely to defect in later rounds.

Interestingly, in this first version of the experiment, Moreno found little difference between the lattice and scale-free structure.

Postulating that this was due to the static nature of the network, Moreno devised a different experiment: players were placed in an initial network structure, but they had the option to cut or add connections to other people. New connections were always reciprocal, with both parties having to agree to the connection.

He then ran this experiment over several different parameters, with some games allowing players to see each others past actions and other games having no memory.

In the setting where people could see past action, cooperation was significantly higher – about 20-30% more than expected otherwise. People who chose to defect were cut out of these networks and ultimately weren’t able to benefit from their defecting behavior.

I found this particularly interesting because earlier in the talk I had been thinking of Habermas. As interpreted by Gordon Finlayson, Habermas thought the result of standard social theory was “a false picture of society as an aggregate of lone individual reasoners, each calculating the best way of pursuing their own ends. This picture squares with a pervasive anthropological view that human beings are essentially self-interested, a view that runs from the ancient Greeks, though early modern philosophy, and right up to the present day. Modern social theory, under the influence of Hobbs or rational choice theory, thinks of society in similar terms. In Habermas’ eyes, such approaches neglect the crucial role of communication and discourse in forming social bonds between agents, and consequently have an inadequate conception of human association.”

More plainly – it is a critical feature of the Prisoners Dilemma that players are not allowed to communicate.

If the could communicate, Habermas offers, they would form communities and associate very differently than in a communications-free system.

Moreno’s second experiment didn’t include communication per se – players didn’t deliberate about their actions before taking them. But in systems with memory, a person’s actions became part of the public record – information that other players could take into account before associating with them.

In Moreno’s account, the only way for cooperators to survive is to form clusters. On the other hand, in a system with memory, a defector must join those communities as a cooperative member in order to survive.


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