it’s a small e-mail world after all

More than 30 years ago, research by psychologist Stanley Milgram suggested that any person on the planet can be connected to any other person by an average of six social ties. This “small-world hypothesis” with its famed “six degrees of separation” caught on in popular culture, inspiring the Kevin Bacon game, where movie stars are connected through a chain of film work to the actor. And it seems to work for e-mail as well, report researchers in the August 8 Science. Peter Sheridan Dodds of Columbia University and his colleagues asked volunteers to attempt to reach 1 of 18 people from 13 countries by forwarding messages to acquaintances. Targets included a professor at an Ivy League university, an archival inspector in Estonia, and a vet in the Norwegian army. Of the more than 24,000 message chains that were generated, only 384 reached their target, but of those successful 384, just as in Milgram’s experiments, the searches took between 5 to 7 steps. There was evidence that the low chain completion was due to “individual apathy and disinclination to participate.” The researchers write, “if individuals searching for remote targets do not have sufficient incentives to proceed, the small-world hypothesis will not appear to hold, but that even a slight increase in incentives can render social searches successful under broad conditions.”

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 8/12/2003.