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 Victor MacGill
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Six
Degrees of Separation
Stanley Milgram designed an experiment back in 1967 where he gave a message to people living in the mid-west of the United States and asked them to send it to a stockbroker living in Boston. Rather than just posting it, if they did not personally know the stockbroker, they had to post it to someone they knew on a first name basis, who was more likely to know him and they had to do likewise, until the message finally arrived. He was interested to know how many steps were needed on average to make such a link. With such an enormous population in the united States, we might be tempted to think a large number of steps would be needed. Of course, small work network dynamics tells us that if we can get our message out of our local cluster we soon have potential links with an exponentially growing list of people at each step. If we can link in with a “hub person”, who knows so many more people than most, the process may be sped up even more. Stanley Milgram found the number of steps on average was six. From which the saying “six degrees of separation” has come into our common language. There has been some controversy over this, however, as later researchers found that around 95% of the messages sent, never actually arrived at the destination, suggesting that perhaps the idea has grown into an urban myth. The messages may not have arrived because the chains broke down. The more steps there are; the more likely it is that a particular person did not send the message on. Each person also does not know if the pathway they have chosen, will in fact be the shortest route to the destination. Since 2001, Duncan Watts through the University of Columbia, has been replicating his experiment, also using emails, which are more likely to be passed on. He has worked with 48,000 senders and 19 targets covering in 157 countries. His results suggest that six is in fact around the average number of steps to link any two people anywhere on the planet. A variant of this experiment links movie actors in the “Bacon Game”. In this a person is deemed to be linked to another if they have stared in a movie with another actor. Each actor is given a Bacon Number depending on the number of steps to link back to actor, Kevin Bacon. He has a number of zero, while Elvis Presley has a Bacon number of two, because he starred in Change of Habit with Edward Asner, who starred in the movie JFK with Kevin Bacon. There is a similar number called an Erdős number named after Paul Erdős, a Hungarian mathematician. He traveled widely around Europe writing papers with other scientists and mathematicians. A link is defined by having collaborated with another person on a scientific paper. Benoit Mandelbrot has an Erdős number of two, while Stephen Hawking’s number is three. |
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