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The phrase "six degrees of separation" represents the idea that anyone in the world can be connected to anyone else through a chain of acquaintances with no more than five people in between. The idea first gained light in a 1929 short story called Chains by Hungarian writer Karinthy Frigyes.

It's a Small World

More generally, this idea is part of the so-called small world phenomenon. In the 1950s, two researchers set out to prove the theory mathematically but did not meet with quick results. In 1967, noted social psychologist Stanley Milgram carried out a series of experiments to test the problem using real-world social networks.

Milgram randomly selected people to send postcards to a particular target. The senders knew the recipient's name, occupation, and general location. They were instructed to send the card to a person they knew on a first-name basis who they thought was most likely, out of all their friends, to know the target personally. That person would do the same, and so on, until the postcard reached the target.

Although the participants expected the chain to include many intermediaries, almost all were less than six steps.

Artificial Intelligence

Milgram's experiment is an example of local search, a topic covered in introductory sessions of CMPSCI 383 as well as, undoubtedly, any undergraduate course in artificial intelligence.

A local search starts out at a given point in the network — the first person — and moves along to each successor in the path. At any given point in the path, the only parts of the network being searched are those adjacent to the current point. In our example, each person — each point on the path — performs a "local search" on all of their acquaintance and then passes the letter on to the best candidate friend, who then performs another local search, and so on.

Local search is surprisingly effective.

Our Experiment

User:GMorehou is attempting to conduct this experiment on Facebook as an extracurricular activity for CMPSCI 383.

The Medium

Although this experiment has been conducted before by e-mail, Facebook appears to be an interesting and fairly good medium for our attempt. Generally the majority of friend relationships on Facebook are based upon two people having met face to face at least once. Facebook intuitively feels like a great medium on which to coduct this experiment, and it also seems as though college students may be more likely to participate in such a trial.

Due to the digital, searchable nature of the medium, certain challenges are presented. If the full name and target network of the recipient were given, people could simply run a search and forward the letter directly. Therefore, the destination address will necessarily have to be even fuzzier than the ones given in Stanley Milgram's experiment!

The destination address will contain several clues, none of which alone or together are enough to pinpoint the recipient to a particular local Facebook network.

The Letter

Creation of unique letters

The text of the letter is standard. New copies of the letter with unique IDs will be created by users visiting a web application tied into the Facebook API. This web application will only allow one letter per verified Facebook user and will keep track of generated letter IDs in order to prevent mass injection of unique, registered letters into the network.

The web application will keep track of the following information for each letter generated:

• issue date
• first name of requester
• last initial of requester (optional)
• occupation of requester (optional)
• Facebook network of requester
• Facebook ID of requester (not publicly disclosed)

Persons uncomfortable with this information being stored by the application and publicly disclosed (with the exception of the Facebook ID) should not participate.

Text of the letter

Below is the standardized text of the letter. A unique ID and list of forwarders is included as an example.