Homophily

What is Homophily?

Homophily is the tendency for social connections to occur more often between similar people. The similarity might involve age, education, beliefs, interests, or other characteristics.

How homophily works

People do not choose friends from a random sample of the population. Schools, workplaces, neighborhoods, and clubs shape whom they meet. Personal preferences can add further similarity within that available pool.

McPherson, Smith-Lovin, and Cook's review distinguishes similarity arising from contact opportunities from additional similarity beyond that baseline. Both help explain the structure of social networks.

Homophily versus social contagion

Consider friends who belong to a running club. They may have joined because they already liked running. They may also encourage each other to run more. Shared interests and social influence can operate together.

Social contagion concerns behavior spreading through social connections. Homophily concerns similarity in those connections. Seeing similar behavior among friends does not tell you which process produced it; shared circumstances offer another explanation.

Why homophily matters

Who knows whom affects how information and opportunities travel. A network of similar people can repeatedly circulate the same views and miss others. But a snapshot of that network cannot establish that friends caused one another's beliefs or behavior. You need to know how the relationships and similarities developed.