Two people with a mutual acquaintance are unusually likely to connect, which closes networks into clusters.
Simmel's insight, and the reason social networks cluster rather than spreading evenly. It is also why introducing two friends changes your relationship with both.
In practice
- Two colleagues introduced at a leaving do are working together within the year, and the person who introduced them is in neither conversation.
- A newcomer to a village is invited to one supper and knows fourteen people by Christmas, because each introduction pulls in the rest of the table.
- Further reading
- Wikipedia
- Subject
- Networks & Collective Behavior
- Essay
- How connections shape what crowds do