In order to test their theories on human cooperation, researchers Gianluca Grimalda, Andreas Pondorfer (both Kiel Institute for the World Economy), and David P. Tracer (University Colorado, Denver) visited the Teop people of Papua New Guinea, a small-scale community that is very different from Western societies. The Teop people are horticulturalists and foragers. They use rudimentary tools to grow their food, they have no mechanized industry, and payment for labor is rare. They live in villages of approximately 150 people. This type of small-scale society is ideal for testing evolutionary theories of human behavior as the conditions within them are much closer to those experienced throughout most of our evolutionary history—unlike Western industrialized societies. The Teop field study, one of the first to examine the effects of real-life social image on human cooperation, has just been published in Nature Communications.
According to evolutionary and economic theories, humans, like other animals, are expected to behave selfishly, maximizing material gains for themselves. Since cooperation involves sacrificing self-interest for the interests of the group, cooperation should have been wiped out by natural selection. Yet human cooperation still occurs in all known societies. This is a scientific puzzle that demands explanation. Several theories have been proposed to explain the evolution of cooperation. In the Teop field study, the researchers focused on two of the most common ones: social image concerns and the propensity to punish deviant behavior. The former theory describes the desire of the individual to maintain his or her reputation as a cooperator in the social group. The latter emphasizes the capacity of human groups to “self-enforce” cooperation norms, with some individuals acting as “vigilantes,” who are prepared to sacrifice their own resources to punish those who do not cooperate.
The relevance of social image concerns was tested among the Teop people through the presence in some sessions—but not in others—of a “Big Man” (community leader) as an observer of participants’ decisions in anonymous cooperative interactions, the so-called Prisoner’s Dilemma game. In the absence of effective formal institutions, the Big Men are responsible for solving social disputes and enforcing social norms. They also serve as the “hubs” of social networks and are the figures toward whom individuals in the community strive to maintain a positive social image.
The key finding of the study is that social image concerns far outweigh punishment as factors that promote the efficiency of cooperation in this society. Interestingly, when a Big Man from an external group acts as the observer, there is no positive influence on cooperation. Social image concerns therefore appear limited to the individual’s own social group. Overall, these results support the view that a concern for one’s social image is a universal trait in human psychology. Conversely, the propensity to punish non-cooperative behavior, which is observable in some contemporary societies, is likely to have been acquired relatively recently in human evolution. The study concludes that the desire among individuals to maintain a positive social image within the community is more important than punishment as a driver of social cooperation.