It seems quite intuitive, but scientists have officially proved it - sharing common knowledge with someone makes you more likely to cooperate with him. This provides valuable insight into how altruism works, and how groups can cooperate towards a common goal.
There have been plenty of studies into altruism, but fewer have studied its lesser known "cousin" - mutual cooperation; that is, when people cooperate to help others, and themselves. To analyze this phenomenon, a group of researchers, including authors Steve Pinker (known for his advocacy of evolutionary psychology and the computational theory of mind) designed four games, which involved 1,033 people. The games involved giving subjects various pieces of information, from private to common. The common information was literally broadcasted over a loudspeaker. Each person was then asked to make a set of decisions, each with varying costs and rewards, choosing to work alone or with other volunteers.
What researchers observed was that when people have common knowledge, and they know that they have this common knowledge, are much more likely to cooperate with one another. Especially if the information they have is private (like if they know a secret):
“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.”
Indeed, this finding has many ramifications, from understanding how social media can affect users, to more deep social action and interaction. The implications vary greatly, from the big and extraordinary, to the small and ordinary; for example, this behavior can overthrow dictators, but is also responsible for something as mundane as blushing:
“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.”
Another researcher from the team, Kyle Thomas, emphasizes the importance of this finding:
“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.”
It's not yet clear why this type of behavior occurs, but it likely has evolutionary roots. The researchers haven't directly tackled the cause, but they 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.”
Journal Reference: Kyle A.; DeScioli, Peter; Haque, Omar Sultan; Pinker, Steven. The Psychology of Coordination and Common Knowledge. Journal of Personality and Social Psychology, Aug 11 , 2014, No Pagination Specified.