What motivates you to help a friend move, to hold a door open for a stranger, or to go out of your way to help neighbors carry their groceries? In other words, what drives you to help or cooperate with other people when it isn't in your personal best interest?
That question of what promotes cooperation, particularly against one's own self-interest, drove Gianluca Grimalda's latest research. Dr. Grimalda turned to the Teop, a small population in Papua New Guinea, to investigate.
And, at least among the Teop, Grimalda found that concern over one's social reputation best promoted cooperation with others.
Grimalda and his colleagues tested two theories of cooperation in experimental games with Teop subjects. One theory held that punishment was the best mechanism to promote cooperation, while the other suggested that people acted cooperatively to be seen in a positive light in their community.
The experiment went like this: Each participant was given 10 Papua New Guinean kina (about $3). They were told that they could either keep the money for themselves or give it to another, anonymous member of their village who was also playing the game.
It seems like an obvious choice to keep the money for yourself, but the researchers added a twist. If they chose to give the money away, the other person would receive 20 kina. So if both players chose to give the money to the other, that is to say, if they cooperated, they would collectively bring back 40 kina to their home village, the best case scenario for the society as a whole. But if one chose to cooperate and one chose to keep, the player that chose to keep the money would end up with 30 kina and the cooperative player would take home nothing.
Each player had to make his or her choice without knowing what the other person would do, in a scenario known as the prisoner's dilemma. In such a dilemma, the best case scenario for all is to cooperate, but it might not seem like the most rational decision for an individual who has to make a choice without knowing what the other person will do.
Under these conditions, 47.1 percent of participants in Grimalda's study chose to cooperate.
But when researchers had a village leader, called the Big Man, observe the game, 63.9 percent of players cooperated.
To determine whether it was merely the presence of an authority figure influencing the outcome, Grimalda had a Big Man from a different linguistic background observe players, and during those games they cooperated just 40.7 percent of the time. He suggests this indicates that the players were concerned about how their choices would influence how the Big Man sees them and therefore their reputation in their villages.
But what about the fear of punishment?
Grimalda also introduced an element of punishment both with and without the presence of the Big Man. And still, the presence of a local leader had the strongest influence promoting cooperation.
Still, Jillian Jordan, a Ph.D. candidate at Yale University who was not part of the study but who's own research has focused on cooperation, says that fear could still be playing a role.
"The reason that we care about people observing us is that ultimately the things they observe will affect how they interact with us in the future," Ms. Jordan tells The Christian Science Monitor. It's an issue of implicit rewards or implicit punishments, she explains.
"The idea is that cooperation is all about paying a short-term cost to help somebody else," she says. "We think about cooperation as being beneficial in the long-run," for example you might help a friend now and they'll help you later. But if you don't help them, they might turn on their heels when you ask for help in the future. The presence of the local leaders could have the same effect on players, Jordan suggests.
Other studies have found a stronger relationship between punishment and cooperation. For example, a study published in February suggested that the belief in a punitive, moralistic, all-knowing deity also promoted prosocial behavior.
"We still know very, very little," Grimalda tells the Monitor. And this is likely because the mechanisms promoting cooperation are "extremely culturally dependent."
Most psychological studies have focused on Western societies, Grimalda says.
But focusing on smaller, less complex societies may help researchers better get at the origins of human behavior, suggests Jordan. This study is a good example of "a very different data point that we get than testing undergraduates at an elite university."
Jordan and Grimalda both advocate for more cross-cultural research to better understand "such a defining feature of our humanity," as Jordan calls cooperation.
Grimalda says cooperation has likely had two key impacts on human society: an economic one and an evolutionary one.
Economically, he explains, it is difficult to set up trade or business communities without trusting others. Early human cooperation likely laid the groundwork for more complex economies and trade networks.
Evolutionarily, "humans are a species that has developed this incredible capacity to adapt to more or less every physical environment," Grimalda says. Somehow along the way, humans must have figured out that it was most effective "to face the problems of adaptation to physical environments working as a group rather than as an individual."
Grimalda and his colleagues' research is published in a paper Tuesday in the journal Nature Communications.