The concept of ?six degrees of separation,? which is the idea that there are only 6 people between you and anyone you want to reach, came from an experiment performed in 1967 by social psychologist Stanley Milgram, who sent packages to several hundred randomly selected people in the Midwest, with the aim of getting them delivered to target people in Boston.
Each recipient was given some details about the target recipient, such as their name and profession, and was asked to send the package to a personal acquaintance they believed was more likely to know the target personally. Milgram discovered that on average the packages reached their targets after passing through only about six people. In 1998, mathematicians Duncan Watts and Steven Strogatz at Cornell University showed that Milgram?s finding can be explained by the ?small world effect,? in which just a few people with many different friends can quickly network through otherwise huge networks of acquaintances.
Attempts to replicate Milgram?s findings have had mixed results, and even the original experiment didn?t prove that the ?six degrees? effect holds true for areas outside the U.S.
Now Watts and a team of researchers at Columbia University are now using the internet for a global version of the experiment. They are sending out e-mails that ask people to use their network of acquaintances to get an e-mail message to targets spread across the world. According to Watts, e-mail is ideal for testing Milgram?s claim, since there are over 100 million e-mail users worldwide.
Only e-mails between genuine acquaintances will be counted as completing a chain. People will not be allowed to take a short cut by just looking up the target?s e-mail address.
Watts has set up a website giving details about how to take part, and how to volunteer to act as a target. ?Ideally, we?d like to have, say, 100,000 people, each trying to reach around 20 targets,? he says. The team wants as many people take part as possible, because they suspect people?s dislike of spam might otherwise ruin their experiment. Early tests show that only one in four e-mails are being passed on, so many thousands of people will have to take part for even one chain of acquaintances to reach the target.
So scan your spam carefully, before you push the ?delete? button. ?Perhaps people can?t be bothered to pass them on — or perhaps Milgram was just wrong,? says Watts. ?Either way, we need lots of people to take part so we can tell.?
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Six degrees of separation can also be applied to sexual relationships. Luis Amaral, of Boston University, wanted to find out if safe sex campaigns could be more effective if they targeted only the most promiscuous people in a community.
?It?s the people with many partners who have a big impact on how sexually transmitted diseases spread,? he says. ?We need to be able to identify people who are likely to fall into this category in the future and target campaigns at them.?
In order to figure out the number of sexual links needed to connect people, Amaral and his colleagues at Stockholm University studied data from a sex survey of 2,810 people. By checking how many sexual partners people had in one year, they could estimate the number of sexual liaisons needed to link two people. ?We found it could be much less than six,? says Amaral.
When it comes to sex, six degrees is not nearly enough. Amaral says, ?If you have someone who has hundreds of partners, there?s a good chance they’ll be in contact with someone that has a sexually transmitted disease — they can then pick that up and pass it on to a lot of others.?
To read about the scientific investigation of another “old wives tale,” click here.
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