Editing Stanley Milgram (section)

==Small-world phenomenon==
{{main|Small-world experiment}}
The [[six degrees of separation]] concept was examined in Milgram's 1967 "small-world experiment", which tracked chains of acquaintances in the United States. In the experiment, Milgram sent several packages to 160 random people living in Omaha, Nebraska, asking them to forward the package to a friend or acquaintance who they thought would bring the package closer to a set final individual, a stockbroker from Boston, Massachusetts. Each "starter" received instructions to mail a folder via the U.S. Post Office to a recipient, but with some rules. Starters could only mail the folder to someone they actually knew personally on a first-name basis. When doing so, each starter instructed their recipient to mail the folder ahead to one of the latter's first-name acquaintances with the same instructions, with the hope that their acquaintance might by some chance know the target recipient.

Given that starters knew only the target recipient's name and address, they had a seemingly impossible task.  Milgram monitored the progress of each chain via returned "tracer" postcards, which allowed him to track the progression of each letter. Surprisingly, he found that the very first folder reached the target in just four days and took only two intermediate acquaintances. Overall, Milgram reported that chains varied in length from two to ten intermediate acquaintances, with a median of five intermediate acquaintances (i.e. six degrees of separation) between the original sender and the destination recipient.

Milgram's "six degrees" theory has been severely criticized. He did not follow up on many of the sent packages, and as a result, scientists are unconvinced that there are merely "six degrees" of separation.<ref>{{cite web|url=http://www.uaf.edu/northern/big_world.html |title=Could It Be A Big World After All? |publisher=Uaf.edu |access-date=June 22, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090301152432/http://www.uaf.edu/northern/big_world.html |archive-date=March 1, 2009 }}</ref> Elizabeth DeVita–Raebu has discussed potential problems with Milgram's experiment.<ref>{{cite web|author=Elizabeth DeVita–Raebu |url=http://discovermagazine.com/2008/feb/if-osama.s-only-6-degrees-away-why-can.t-we-find-him |title=If Osama's Only 6 Degrees Away, Why Can't We Find Him? &#124; Human Origins |publisher=DISCOVER Magazine |date=January 28, 2008 |access-date=June 22, 2009}}</ref>

In 2008, a study by Microsoft showed that the average chain of contacts between users of its '.NET Messenger Service' (later called [[Microsoft Messenger service]]) was 6.6 people.<ref>{{cite arXiv|eprint=0803.0939 |title=Planetary-Scale Views on an Instant-Messaging Network|author1=Jure Leskovec|author2=Eric Horvitz|class=physics.soc-ph|year=2008}}</ref>