A crucial task in the analysis of on-line social-networking systems is to identify important people — those linked by strong social ties — within an individual’s network neighborhood. Here we investigate this question for a particular category of strong ties, those involving spouses or romantic partners. We organize our analysis around a basic question: given all the connections among a person’s friends, can you recognize his or her romantic partner from the network structure alone?
Using data from a large sample of Facebook users, we find that this task can be accomplished with high accuracy, but doing so requires the development of a new measure of tie strength that we term `dispersion’ — the extent to which two people’s mutual friends are not themselves well-connected. The results offer methods for identifying types of structurally significant people in on-line applications, and suggest a potential expansion of existing theories of tie strength.