Kleinfeld assumed that Milgram’s study must have been replicated for his results to have been so widely and enthusiastically accepted. Confirming the validity of a finding by repeating experiments is, after all, a hallmark of the scientific process. Kleinfeld scoured the academic literature but found only two follow-up studies, one done by Milgram himself. And neither one, Kleinfeld says, substantiated the six-degrees claim. “I was disappointed in Milgram, who was one of my idols, for avoiding the limitations of his research in the arresting and well-written article he had published in Psychology Today,” Kleinfeld says. “My students, however, were not surprised. The results supported their notions of the limitations of social research.”

Was Milgram so in love with the idea of six degrees that he overlooked the weak statistics.

Milgram had said that he got the idea for his small world study from social scientist Ithiel de Sola Pool and mathematician Manfred Kochen, who, in the 1950s, spent a good deal of time trying to arrive at a mathematical formula that would explain how closely all of us are actually connected. But de Sola Pool and Kochen were unable to find an equation that satisfactorily represented the nuances and complexities of society. Milgram, who was already famous for the obedience experiment in which study subjects administered painful electric shocks to other study subjects when urged to do so by an authority figure, came up with the letter method as a tool to try to solve the problem in real life.

Usually scientists publish in academic journals first, and then bring their results to the lay press. Milgram did it in reverse by publishing first in Psychology Today. “This allowed Milgram to sidestep the usual publication lag in academic publishing,” explains Thomas Blass, a professor of psychology at the University of Maryland and author of The Man Who Shocked the World: The Life and Legacy of Stanley Milgram. But in writing for the lay public, Milgram omitted statistics—the numbers that would show how few of his chains were in fact completed. Milgram did publish the actual results of his second study, including the statistics, in an academic journal a couple of years later, pondering at length the reasons for the low completion rates of the chains.

Kleinfeld’s interpretation of all this—which she also published in Psychology Today (March/April 2002)—is that Milgram was so in love with the idea of six degrees that he overlooked the weak statistics backing it up. And worse, he promoted his sketchy results to an unsuspecting public. Not that she thinks the public minds. In talking to others about their coincidental experiences running into friends and friends of friends in unlikely places, she’s become convinced that the idea of six degrees has deep psychological appeal. “The belief in a small world gives people a sense of security,” she says.

But that’s not really the end of the story. In the interval between Milgram’s work and Kleinfeld’s digging through those boxes, a field known as the science of networks had blossomed. “Just about anything in the social, biological, and physical world has to do with systems that comprise lots and lots of interacting components,” says Duncan Watts, a professor of sociology at Columbia University. It’s important to understand how networks function because, as Watts puts it, “that has relevance to just about every question we’re interested in, whether we’re talking about the spread of epidemics, or changes in social norms, or fashions, or the expression of the genome.” It’s all about some sort of process driven by many things interacting with one another. “And the interactions,” Watts believes, “are critical.”

In 1998 Watts and Steven Strogatz, a professor of applied mathematics at Cornell University, published a paper in Nature that did what de Sola Pool and Kochen hadn’t done: It provided a mathematical explanation for how random people living far apart can be linked by a handful of connections. The concept rests upon the idea that we all lead multidimensional lives. “People organize their lives along different social dimensions,” explains Watts. “I know some people because of what I do for work, some because of where I live, and others because of where I grew up. A professional colleague and someone I grew up with may look at one another and not think they have anything in common, but I form the bridge because I’m close to each one of them.”

It’s these acquaintances that allow us to cut through the swaths of humanity, and many social dimensions, to reach people who seem far removed from ourselves. But what of the enormous attrition rate in Milgram’s study, which Kleinfeld found so damning? Milgram, in the results he published in the scientific literature, speculated that study participants hadn’t completed their chains because they lacked motivation or didn’t really believe that they could reach their targets. Watts tends to agree with that argument—largely because he’s seen it in action.

In 2003 Watts published the results of an e-mail version he did of Milgram’s experiment. He set up a Web page and recruited 18 targets in 13 countries. In the end, 61,168 starters signed on, and 24,163 chains were begun. Of those, only 384 were completed. Those who finished their chains did so within slightly more than four links, on average. Watts, unlike Milgram, included a survey with his study, and one of the questions asked people who hadn’t finished to give the reason why. Less than one-half of 1 percent of respondents said they had failed to pass the e-mail on because they didn’t know who to send it to. Watts believes the majority failed because of other problems, such as e-mail spam blocks that diverted their requests. Other times, he suspects, chains failed because the people who received an e-mail weren’t as interested in continuing the chain as the people who’d started it.

“People so much want to believe that we live in a global village, all holding hands,” Kleinfeld says.

Lack of interest, Watts says, points to the underlying complexity of networking. The question is not just whether we are closely connected, but how we navigate those connections—and whether we choose to do so at all. “People can find these paths as long as they’re motivated to do so and able to motivate people to help them,” he says. “But no matter how motivated you are, you have to be able to motivate the other person, who can put you in touch with the next person, and the next person has to do it too.”

According to Watts, sometimes those in the best position to help you aren’t inclined to do so. This would undoubtedly be a problem if the CIA, say, tried to connect with Osama bin Laden. “If you’re trying to reach bin Laden, the last couple of people in the chain are not going to be particularly cooperative, even if they could be,” says Watts.

There’s also the issue of belief. Some people just don’t believe we can be linked by so few people, so they don’t try to connect. But the perception of connectivity is crucial in completing the chains. Take the example of Petey Pierre, a student and boxer who worked out at the Bedford-Stuyvesant Boxing Center in Brooklyn, New York.

In 2006 Pierre agreed to participate in a small world experiment with Watts and ABC News that addressed two of the criticisms of small world research: that no studies had ever been played out in real time, and that the people who had participated in the chains tended be educated, white, and middle or upper class. Critics say it’s easy to show how predominantly middle-class professional people can connect to one another in different countries. But add race and socioeconomic status and it’s a different ball game.

So ABC recruited Petey Pierre and Kristina Stewart Ward, then an editor for Hampton Style magazine who split her time between the Upper East Side of Manhattan and the Hamptons on Long Island, where she hobnobbed with celebrities. Ward’s assignment: Get to Pierre.

Ward was sure she could connect with him in just a couple of steps. She first called her friend James, who worked at Asprey, a store known for its luxury jewelry. She remembered having a conversation with him once in which he mentioned a fellow employee who boxed. James promptly put her in touch with that person, a woman named Michelle. Michelle put Ward in touch with her trainer, Michael Olajide, a former middleweight contender, who owned a gym in Manhattan’s fashionable Meatpacking District. He directed Ward to Bruce Silverglade, owner of Gleason’s Gym in Brooklyn. As it turned out, Silverglade not only knew of Pierre’s Bedford-Stuyvesant gym, he knew Nate Boyd, Pierre’s trainer. It was Boyd who made the final connection. When Ward arrived at the gym, both Pierre and Watts were there. “It was amazing,” Watts recalls. “Pierre was blown away.”

Unlike the people who participated in Milgram’s and Watts’s experiments, Ward and Pierre were motivated by a camera crew and a mention on ABC News. Most people don’t have that. Nevertheless, for Watts the TV experiment provided another bit of evidence that the idea of six degrees of separation has a lot of truth behind it. Kleinfeld is more skeptical. “I still find one of the most interesting questions to be why people so much want to believe that we live in a global village, all holding hands.”