It is clear from bacteria to ourselves that cooperation has evolved many times in all sorts of organisms and so it clearly has an advantage that can be realized. However, it is also obvious that simple unquestioned cooperation works if everyone cooperates but would be a great disadvantage once cheaters became numerous. This looks like a paradox – it evolves but why. Cooperation is especially important to humans. You cannot develop our sort of civilization – do neurosurgery or send rockets to the moon or use language – as lone uncooperative individuals.
Two types of cooperation do seem to fit in an evolutionary picture – cooperation between related animals (kin), and reciprocity/trading favours. It is easy to see how these would arise in evolution and be stable. Also (if you accept group selection) groups that were predominately cooperators could out perform groups that were mostly cheaters. Group selection may only work well if the groups are on the small side and then it would be hard to separate this from helping kin and reciprocal relationships. But how does cooperation survive in the large society starting with both cooperators and cheaters?
The Prisoner’s Dilemma game has been used for many years with various modifications (both played by people and by programs) to find the conditions that are needed for cooperation to lose its disadvantages. One of the first fairly successful modifications was ‘tit-for-tat’ in various forms. If someone does not cooperate with you on some occasion then you do not cooperate with them in future. In a population that starts with lots of cooperators and few cheaters, the cheaters will be frozen out of any cooperation and the cooperators will flourish. The models were improved with more ingredients. By itself it is not quite good enough. Another ingredient is punishment of cheaters over and above tit-for-tat. For example cheaters can lose their reputation or in some other way carry a sign that says, “I’m a cheater.” Or a cheater could be directly punished by the individual that was hurt, or by the whole society, or by 3rd party punishers. They can be banished from the group or from participating in particular activities. We humans seem to have a built in joy in cooperating, but also a pleasure in gossip about people who are not worthy, and a need for justice and/or revenge for those that take advantage of our trust.
A recent paper (citation below) by Hoffman and others, examines the idea of examining a person’s motives in deciding whether they are trust worthy. “Why do we trust people more when they do good without considering in detail the cost to themselves? People who avoid “looking” at the costs of good acts can be trusted to cooperate in important situations, whereas those who look cannot. We find that evolutionary dynamics can lead to cooperation without looking at costs. Our results illuminate why we attend closely to people’s motivations for doing good, as prescribed by deontological ethicists such as Kant, and, also, why we admire principled people, adhere to taboos, and fall in love.”
Here is the abstract: “Evolutionary game theory typically focuses on actions but ignores motives. Here, we introduce a model that takes into account the motive behind the action. A crucial question is why do we trust people more who cooperate without calculating the costs? We propose a game theory model to explain this phenomenon. One player has the option to “look” at the costs of cooperation, and the other player chooses whether to continue the interaction. If it is occasionally very costly for player 1 to cooperate, but defection is harmful for player 2, then cooperation without looking is a subgame perfect equilibrium. This behavior also emerges in population-based processes of learning or evolution. Our theory illuminates a number of key phenomena of human interactions: authentic altruism, why people cooperate intuitively, one-shot cooperation, why friends do not keep track of favors, why we admire principled people, Kant’s second formulation of the Categorical Imperative, taboos, and love.”
Hoffman, M., Yoeli, E., & Nowak, M. (2015). Cooperate without looking: Why we care what people think and not just what they do Proceedings of the National Academy of Sciences, 112 (6), 1727-1732 DOI: 10.1073/pnas.1417904112