I was reading about graph theory earlier, particularly about the shortest path problem, when I came across the concept called six degrees of separation. According to Wikipedia, it refers to the idea that, “if a person is one step away from each person he or she knows and two steps away from each person who is known by one of the people he or she knows, then everyone is an average of six ’steps’ away from each person on Earth.”
This idea was first proposed by social psychologist Stanley Milgram. In his experiment, participants were asked to forward a package to certain people. If the participants knew the intended recipient personally, they can forward the package directly. If not, they can forward the package to someone else whom they think knows the recipient. On an average, it took six links to deliver the package to the recipient. Milgram’s experiment, however, was criticized for being conducted on a small population. Furthermore, a lot of those who received forwarded packages refused to forward it further.
Since Milgram’s experiment, similar experiments have been performed. In 2001, professors at Columbia University conducted a large-scale version of Milgram’s experiment, involving over 60,000 participants from 166 countries with email as a medium. The result is a median chain length of between five and seven people.
The concept, however, is still not without criticism. For instance, critics say that it would be improbable to find a chain to anyone belonging to isolated populations that has no contact with those from outside their culture, such as the recently discovered tribe in Brazil. Such populations though form only an estimated 1% of the total global population and thus the six degrees of separation would still be possible.
Scientists have a particular interest in the six degrees of separation, and social networks in general, because it could provide a clue, for instance, on how disease is spread, or how a criminal can be caught. I think the six degrees of separation also goes to show how much impact one person could make. “Save the cheerleader, save the world”, as one TV show would say.
Juan Guare, an American playright, in his play Six Degrees of Separation, which is based on the concept, wrote, “I read somewhere that everybody on this planet is separated by only six other people. Six degrees of separation between us and everyone else on this planet. The President of the United States, a gondolier in Venice, just fill in the names. I find that extremely comforting, that we’re so close, but I also find it like Chinese water torture that we’re so close because you have to find the right six people to make the connection. It’s not just big names — it’s anyone. A native in a rain forest, a Tierra del Fuegan, an Eskimo. I am bound — you are bound — to everyone on this planet by a trail of six people. It’s a profound thought. . . How everyone is a new door, opening into other worlds.”