Could it be a Big World after All?
Abstract
The idea that people are connected through just "six degrees of separation," based on Stanley Milgram's "small world study," has become part of the intellectual furniture of educated people. New evidence discovered in the Milgram papers in the Yale archives, together with a review of the literature on the "small world problem," reveals that this widely-accepted idea rests on scanty evidence. Indeed, the empirical evidence suggests that we actually live in a world deeply divided by social barriers such as race and class. An explosion of interest is occurring in the small world problem because mathematicians have developed computer models of how the small world phenomenon could logically work. But mathematical modeling is not a substitute for empirical evidence. At the core of the small world problem are fascinating psychological mysteries.
The "small world problem" takes its name from an experience familiar to us all. As Milgram (1967) describes it:
Fred Jones of Peoria, sitting in a sidewalk cafe in Tunis, and needing a light for his cigarette, asks the man at the next table for a match. They fall into conversation; the stranger is an Englishman who, it turns out, spent several months in Detroit studying the operation of an interchangeable-bottlecap-factory. "I know it's a foolish question," says Jones, "but did you ever by any chance run into a fellow named Ben Arkadian? He's an old friend of mine, manages a chain of supermarkets in Detroit..."
"Arkadian, Arkadian," the Englishman mutters. "Why, upon my soul, I believe I do! Small chap, very energetic, raised merry hell with the factory over a shipment of defective bottlecaps"
"No kidding!" Jones exclaims in amazement.
"Good lord, it's a small world, isn't it?" (p. 61)
The question of how people are hooked up had long been an entertaining parlor game among mathematicians where it took such forms as: If you choose any two people in the world at random, how many acquaintances are needed to create a chain between them? (Kochen, 1989; Garfield, 1979). Ithiel de Sola Pool at MIT and Manfred Kochen of IBM collaborated on mathematical models of the small world problem and circulated unpublished papers within an invisible college of colleagues for two decades. They were reluctant to publish, Kochen (1989) explains, because "we never felt we had 'broken the back of the problem.'" (p.viii)
But Stanley Milgram believed he had solved the problem, or at least made substantial empirical progress, through an ingenious experiment. Milgram (1967) asked "starters," supposedly "randomly" chosen people from psychologically distant locations like Kansas or Nebraska, to send a folder through the mail to a target person in places like Cambridge, Massachusetts or Boston. The starters were given information about the target person and written instructions to send the folder through the mail to someone they knew on a first-name basis who would be more likely to know the target. That person was to send the folder on to someone even closer. Returned tracer postcards tracked the progress of each chain.
Would any folders reach the target person? Milgram was delighted at how fast the answer came. His first target person was the wife of a divinity student living in Cambridge:
Four days after the folders were sent to a group of starting persons in Kansas, an instructor at the Episcopal Theological Seminary approached our target person on the street. "Alice," he said, thrusting a brown folder toward her, "this is for you." At first she thought he was simply returning a folder that had gone astray and had never gotten out of Cambridge, but when we looked at the roster, we found to our pleased surprise that the document had started with a wheat farmer in Kansas. He had passed it on to an Episcopalian minister in his home town, who sent it to the minister who taught in Cambridge, who gave it to the target person. Altogether, the number of intermediate links between starting person and target amounted to two! [emphasis in original] (pp. 64-65) }}}
In a second study, using Nebraska starters and a target who lived in Sharon, Massachusetts and worked in Boston, Milgram (1967) reported that "chains varied from two to 10 intermediate acquaintances, with the median at five" (p. 65). Any person appeared to be able to reach another person with an average of six jumps--the empirical basis for the famous phrase "six degrees of separation."
Milgram's fascinating findings have slipped away from their scientific moorings and entered the world of imagination. The notion that we live in a "small world" where people are connected by only "six degrees of separation" has become part of the intellectual furniture of educated people. "Six Degrees of Separation" is the name of an acclaimed play by John Guare. "Six Degrees of Lois Weisberg" is the title of a famous article by Malcolm Gladwell (1999) explaining how people who span subcultures have enormous social power. "Six Degrees of Kevin Bacon" is a parlor game for movie buffs. "Six Degrees of Separation" is a popular web site, which explains that it was inspired by the idea of six degrees of separation to create a place which would connect millions of people from around the world. "It's a Small, Small World" sing dolls in their national costume at Disneyland in a heart-warming exhibition celebrating the connectedness of people all over the world.
In the digital age, many of us believe, the world has shrunk even more, turning us into a "global village." But is this really the case? Tom Wolfe (2000) argues that the conventional wisdom--that "no person on earth (is) more than six mouse clicks away from any other"--is nothing but "digibabble" (p. 67). People in the western world have been told for over a hundred years, he points out, that technology is making the world smaller and what we have witnessed instead is people banding together along ethnic bloodlines with bloody consequences as in the Middle East and the Balkans. Could our coming together through technology have had the unintended consequence of driving us apart? Cultural groups may set up psychological boundaries when geographic boundaries slip away.