Six Degrees of E-mail Separate Wired World?

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Six Degrees of E-mail Separate Wired World?Stefan Lovgren
for National Geographic News
August 7, 2003

How well do you know Madonna? Do you consider Tiger Woods a buddy? What about former South African President Nelson Mandela?

According to the "small world" theory, you should be just six handshakes away from each of them. But can anyone in the world really reach anyone else through a chain of just six friends?

Yes, say researchers from Columbia University in New York, who have published the first results of their "Small World Research Project."

They identified 18 target people in 13 different countries, then asked participants to get a message through to the target by sending e-mails to friends and acquaintances.

On average, researchers say, people can reach their targets in five to seven steps.

The study also collected demographic data to find out what barriers make it difficult for messages to get through and to deduce what strategy participants use to reach their intended target.

More than 60,000 people participated, creating about 24,000 message chains. Yet less than 400 messages actually reached their targets.

But that failure rate is deceptive. Researchers believe that most people who failed to pass on messages had people they could contact, but simply forgot or didn't want to participate.

"The world is connected, but people don't always believe they are connected," said Duncan Watts, the Columbia University sociology professor who led the project. "It's the perception of connectivity that is most important."

Six Degrees of Separation

In 1967, the social psychologist Stanley Milgram conducted an experiment to test the theory that members of a large social network—in his case, the population of the United States—would be connected through a short chain of intermediate acquaintances.

Milgram sent packets to 400 randomly selected people in Kansas and Nebraska, with the aim of sending the packets to a target person in Massachusetts. He instructed the participants to send the packets to someone they knew on a first-name basis, who they thought was more likely to know the target than they were themselves.

He found that each chain averaged six links, with the final member of the chain being the target itself. The result become popularized through the phrase "six degrees of separation," which became part of both sociology dogma and pop culture, and was the name of a popular 1990 play by John Guare.

A popular parlor game, hosted online by the University of Virginia in Charlottesville, involves finding the shortest route between any given thespian and actor Kevin Bacon. Links are made by appearing in a movie with Bacon, or with someone has appeared with Bacon, and so on.

Among all actors, living and dead, the average number is close to three. No actor has been found to be more than 10 degrees of separation from Bacon.

Proving Milgram

The notion that millions of people are connected by just a few short steps seems obvious in today's digital world where e-mail viruses can shut down half of the world's computers in a click.

But very little empirical research has been done to actually understand the small world network theory.

For their Columbia University project, Watts, who is the author of Six Degrees: The Science of a Connected Age, and his colleagues chose 18 targets, including an American professor at an Ivy League University, an archival inspector in Estonia, an Indian technology consultant, a policeman in Australia, and a veterinarian in the Norwegian Army.

Participants, who found out about the experiment primarily through media stories, were given the name of a target and information about the target's work and location. They were then asked to send a message to someone they knew—and ask them to pass on the message—with the aim of ultimately reaching the target.

"We knew that people who participate in a study like this are often people who are at work, sitting in front of a computer with a few minutes to spare," said Watts. "We designed the program with that in mind."

One chain started with an e-mail from a British military officer, jumped to a finance executive in Uganda, on to an art student in Moscow, then a student in Novosibirsk, Russia, before landing in the inbox of its target, another student in Novosibirsk.

Watts found that successful chains more often involved professional ties than personal ties.

"Weak ties are disproportionately responsible for social connectivity," he said. One explanation for this may be that close friends know the same people as the person who is sending the message.

Watts admits that his project may not be an accurate reflection of the connectivity of the world's entire population. There are, after all, only about 100 million e-mail users. While North America and Western Europe were heavily represented in the project, Africa was not.

Small World Network Models

A separate project, based at Ohio State University in Columbus, is also identifying social structures of e-mail communication networks. Its goal is to create a social map of the Internet to reveal how different types of people are connected and how information moves through society.

"The types of goods that flow through the network—information, ideas and viruses—depend on the social connection between people," James Moody, who is leading the Ohio State project, wrote in an e-mail.

"If we can identify how these networks are shaped, we can better understand information flow, promoting the things we want (information, ideas) and preventing the things we don't want (computer viruses)." Researchers hope the results of their studies will help shed light not only on how people are connected, but on how diseases spread, how people find jobs, how to build better computer networks, and how the global economy operates.

People are indeed connected in principle, but whether or not they are connected in practice depends on their motivation to pursue the search.

"A lot of the world is accessible to you," he said. "If you're determined, you will find what you're looking for as long as you're tenacious about it."

資料來源：http://news.nationalgeographic.com/news/2003/08/0807_030807_email.html