NET NEWS: Pass It On

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Science  08 Feb 2002:
Vol. 295, Issue 5557, pp. 935
DOI: 10.1126/science.295.5557.935e

So your manicurist's cousin's dentist went to kindergarten with the person who trained Michael Jackson's chimp? That's not as ridiculous as it sounds. According to the small world hypothesis, any two humans on the planet are connected by a chain of acquaintances that averages six links. The idea was born in 1967, when Harvard sociologist Stanley Milgram asked 300 randomly chosen Midwesterners to deliver a letter to a person in Boston by sending it through personal contacts. Sixty letters arrived, having passed through an average of six intermediaries.

The finding soon entered pop culture as “six degrees of separation.” But experts wouldn't consider it definitive, as Milgram's sample size was limited, says Columbia University sociologist Duncan Watts. Now Watts and colleagues' Small World Research Project is using the Internet to test the hypothesis on a global scale.

The researchers have begun gathering a diverse group of “targets": So far, recruits include a flight attendant and an employee of a pizza parlor, from as far afield as Siberia. They're also seeking “senders,” each of whom gets only basic data about the target: name, location, occupation. The sender e-mails an acquaintance, who forwards it to another, until, ideally, the message reaches its destination. So far, some missives have gotten through—one traveled from Australia to its Siberian target in only four jumps—while others have stalled. To get a robust sample, Watts needs 100,000 senders and about 20 targets. Find out how to join either end of a chain at

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