<P> Six degrees of separation is the idea that all living things and everything else in the world are six or fewer steps away from each other so that a chain of "a friend of a friend" statements can be made to connect any two people in a maximum of six steps . It was originally set out by Frigyes Karinthy in 1929 and popularized in an eponymous 1990 play written by John Guare . </P> <P> Theories on optimal design of cities, city traffic flows, neighborhoods, and demographics were in vogue after World War I. These conjectures were expanded in 1929 by Hungarian author Frigyes Karinthy, who published a volume of short stories titled Everything is Different . One of these pieces was titled "Chains," or "Chain - Links ." The story investigated--in abstract, conceptual, and fictional terms--many of the problems that would captivate future generations of mathematicians, sociologists, and physicists within the field of network theory . Due to technological advances in communications and travel, friendship networks could grow larger and span greater distances . In particular, Karinthy believed that the modern world was' shrinking' due to this ever - increasing connectedness of human beings . He posited that despite great physical distances between the globe's individuals, the growing density of human networks made the actual social distance far smaller . </P>

Who was the psychologist responsible for popularizing the concept of six degrees of separation