Nnews
Science | DOI: 10.1145/2209249.2209255
Gregory Goth
Degrees of separation
Researchers now have the capability to look at the
small-world problem from both the traditional algorithmic
approach and the new topological approach.
The ideA of six degrees of separation—that is, that ev- ery person in the world is no more than six people away from every other person on
earth—has fascinated social scientists
and laymen alike ever since Hungarian
writer Frigyes Karinthy introduced the
concept in 1929.
iMage by WiKiPedia user dannie-WalKer
For the greater public, the cultural
touchstone of the theory was the 1990
play entitled Six Degrees of Separation
by John Guare. Although the drama
was not an exploration of the phenomenon by any means, it spawned
countless versions of parlor games.
For scientists, however, the wellspring
of the six degrees phenomenon, also
called the small-world problem, was
a 1967 study undertaken by social psychologist Stanley Milgram, in which
a selected group of volunteers in the
Midwestern U.S. were instructed to
forward messages to a target person
in Boston. Milgram’s results, published in Psychology Today in 1967,
were that the messages were delivered
by “chains” that comprised anywhere
between two and 10 intermediaries,
with the mean being five.
In the ensuing years, the problem
has become a perennial favorite among
researchers of many disciplines, from
computer scientists exploring proba-
a study of 721 million Facebook users showed an average of 3. 74 intermediaries between a
source and target user, as opposed to social psychologist stanley milgram’s mean of five.
bilistic algorithms for best use of network resources to epidemiologists
exploring the interplay of infectious
diseases and network theory.
Most recently, the vast architectur-
al resources of Facebook and Twitter
have supplied researchers with some-
thing they never possessed before—the
capability to look at the small-world
problem from both the traditional al-
gorithmic approach, which explores
the probabilities of how each person
(or network node) in a chain seeks out
the next messenger using only the lim-
ited local knowledge they possess, and
the new topological approach, which
