Revisiting six degrees and hubs

In 1967, Stanley Milgram conducted the famous experiment that told us there are six degrees of separation between any two people. He gave letters to 160 people in Nebraska and asked them to pass them along to someone who could eventually get the letters to a particular stock broker in New York. It took about six links for each letter to get to the stock broker.

In 2001, Duncan Watts repeated the experiment, asking 61,000 people to forward emails to eventually reach 18 targets worldwide. The emails took roughly six hops to reach their targets, giving Milgram’s original conclusion more credibility due to the larger sample.

But a secondary conclusion of Milgram didn’t hold up. In Milgram’s experiment, half of the letters reached the target via the same three friends of the stock broker. These people were deemed “hubs.” In Watts’s experiment, only 5% of messages reached their targets via hubs. Watts’s thesis is that while hubs exist — some people are far more connected than others — they’re not as important in spreading ideas as once supposed.

See “Is the Tipping Point Toast?” in the February 2008 issue of Fast Company for more on Duncan Watts and his skepticism regarding the importance of hubs.