Six Degrees of Separation takes its name from the theory that any human being on the planet is linked to everyone else by just six steps or introductions.  We include it in Chapter 9 in its adapted form as a visual research activity which Rob Lakin describes in greater detail here: how to do it and why.

If the theory itself interests you,  you can find all sorts of resources onnline which discuss it , two of which are

• this article in The Guardian newspaper from 2008, purporting to prove that the concept of Six Degrees holds up OR
• this article from Harvard Business Review about the science of the theory