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Common Knowledge Makes Us More Cooperative

People are more inclined to take mutually beneficial risks if they know what others know.
(Photo: Wikimedia Commons)

(Photo: Wikimedia Commons)

If you know that someone knows something that you also know, does that make you more likely to cooperate with them? A new study out of Harvard suggests the answer is yes.

Social psychology has plenty of studies that examine altruism, but there hasn't been much research that looks into its obscure cousin, “mutualistic cooperation”—that is, when people cooperate to benefit each other and themselves.

"Human cognition may have been shaped by natural selection to solve coordination problems."

To start rectifying that, a group of researchers, including the popular author Steven Pinker, designed and ran four game theory-type experiments on 1,033 people that involved giving subjects varying levels of information, from private to common—the common knowledge was literally broadcast over a loudspeaker. Each person was then given a set of decisions with varying costs and payoffs, and allowed to choose whether to work by themselves or with others. In many cases, participants needed common knowledge and others’ help to get the games’ maximum benefit. The researchers also manipulated what their subjects knew about their partners’ knowledge.

The resulting study, published last week in the Journal of Personality and Social Psychology, suggests that when people have common knowledge, they’re much likelier to act in each others’ best interest.

“Because it may be costly to engage in a coordinated activity when no one else does so, attempts to coordinate can be risky when it is unclear what other people will do,” the paper explains. “If one protester shows up he gets shot, but if a million show up they may send the dictator packing.”

Knowing that people make decisions differently when there’s information that’s clearly public has a range of implications, varying from the revolutionary, per the example above, to the ordinary. “The acute discomfort in blushing,” the study suggests, “resides largely in the knowledge that the blusher knows he or she is blushing, knows that an onlooker knows it, that the onlooker knows that the blusher knows that the onlooker knows, and so on.”

As one of the researchers, Kyle Thomas, says, “Common knowledge provides a unifying framework to understand a whole lot of otherwise odd and seemingly disconnected phenomena in human social life.” According to Thomas, people often either try to create common knowledge for a specific aim, like “using Twitter to incite protests in Egypt,” or to avoid it, as when a family doesn't discuss “‘the elephant in the room’ like the problematic drunk uncle that no one wants to confront.”

The inherent value of people having access to the same information probably has evolutionary roots. As the researchers theorize in the paper: “Human cognition may have been shaped by natural selection to solve coordination problems. If game theorists are correct that common knowledge is needed for coordination, then humans might have cognitive mechanisms for recognizing it.”

Rosie Spinks contributed reporting.