91av

IF YOU get unexpected e-mail from an American university over the coming
months, don’t just assume it’s junk. It could be from scientists investigating a
fascinating social phenomenon.

According to urban folklore, everyone in the world knows everyone else via
just a few intermediaries—an effect summed up by the phrase “six degrees
of separation”. The number six emerged from an experiment performed in 1967 by
the social psychologist Stanley Milgram, who sent packages to several hundred
randomly selected people in America’s Midwest, with the aim of getting them
delivered to target people in Boston.

Each recipient was given some details about the target, such as their name
and profession, and was asked to send the package to a personal acquaintance
whom they believed was more likely to know the target personally.

Milgram discovered that on average the packages reached their targets after
passing through astonishingly short chains, typically comprising just 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 handful of people with very diverse friends can “short
circuit” otherwise huge networks of acquaintances
(91av, 6 June 1998, p 7).

But attempts to replicate Milgram’s findings have had mixed results—and
in any case, the original experiment fell far short of proving that the “six
degrees” effect holds true for the whole world. So a team at Columbia University
is now using the Internet to attempt a global version.

Instead of a postal package, they are inviting people to use their network of
acquaintances to get an e-mail message to targets spread across the world.
According to Watts, who devised the experiment, e-mail is ideal for testing
Milgram’s claim as there are well over 100 million e-mail users worldwide. Only
e-mails between genuine acquaintances will be deemed to complete a chain. People
won’t be allowed to short-circuit the sequence by just looking up the target’s
e-mail address.

Watts has set up a website giving full 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 is keen to have as many people take part as possible, not least
because they suspect people’s mistrust of unsolicited e-mail might otherwise
scupper their experiment. Early tests show that barely 1 in 4 e-mails are being
passed on. With such a high rate of attrition, many thousands of people would
have to take part to give much chance of even one chain of acquaintances
reaching the target if Milgram’s six degrees apply worldwide.

“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.”