The original study was replicated in 2003 with email and (of the messages that reached their destination) the median number of connections it took accomplish it was 5 to 7.
To explore just how connected we humans are, in the 1960s the psychologist Stanley Milgram selected about 300 people at random in Nebraska and Boston and asked each of them to start a chain letter. The volunteers were sent a packet of materials with a description of the study, including the name of a “target person”— a randomly chosen man in Sharon, Massachusetts, who worked as a stockbroker in Boston. They were instructed to forward the packet to the target person if they knew him or, if they didn’t, to send it to whichever of their acquaintances they deemed most likely to know him. The intention was that the acquaintance, upon receiving the packet, would also follow the instructions and send it along, until eventually someone would be found who did know the target person and would send it directly to him.
Many people along the way didn’t bother, and broke the chain. But out of the initial 300 or so individuals, 64 did generate chains that ultimately found the man in Sharon, Massachusetts. How many intermediaries did it take until someone knew someone who knew someone who knew someone… who knew the target? The median number was only about 5. The study led to the coining of the term “six degrees of separation,” based on the idea that six links of acquaintanceship are enough to connect any two people in the world. The same experiment, made much easier by the advent of e-mail, was repeated in 2003.18 This time the researchers started with 24,000 e-mail users in more than 100 countries, and 18 different target people spread far and wide. Of the 24,000 e-mail chains those subjects started, only about 400 reached their target. But the result was similar: the target was contacted in a median of five to seven steps.
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