What is homophily in simple terms?

It is the tendency for people to bond with and spend time with others who are similar to them in age, education, tastes or views — the idea behind "birds of a feather flock together."

Are friends similar because of homophily or because they influence each other?

It can be both. People select similar others as friends and also become more alike after becoming friends. Because the two are hard to separate with observational data alone, researchers use experiments and more sophisticated analytic methods.

Homophily

👥 Sociology By CampusDown Wiki Editorial Team Last updated October 27, 2026

Homophily is the tendency for people to form ties more often with others who resemble them in race, gender, age, education, occupation or values, often summed up as "birds of a feather flock together." Conceptualized by Paul Lazarsfeld and Robert Merton in 1954, it became a core concept in social network research through the 2001 review by Miller McPherson and colleagues. It is important for understanding information flow, social segregation and online polarization.

Contents

1. Origins of the concept
2. Selection or influence?
3. Methodological issues and significance
4. FAQ
5. References

Origins of the concept

Studying friendships among residents of U.S. housing projects, Lazarsfeld and Merton (1954) called the tendency to befriend similar people homophily. They distinguished status homophily, ties between people with similar social positions such as race, sex, age, religion, education and occupation, from value homophily, ties between people with similar values, attitudes and beliefs. Synthesizing decades of research, McPherson, Smith-Lovin and Cook (2001) concluded that homophily appears in nearly every kind of tie, including marriage, friendship, work, advice and online connections, with divisions by race and ethnicity the strongest. As a result, they argued, the information people receive, the attitudes they form and the interactions they experience are localized by social position.

Selection or influence?

Following adolescent friendships, Kandel (1978) analyzed whether friends are similar because they selected similar others in the first place or because they became alike after becoming friends, and reported that both processes operate. Analyzing a university email network, Kossinets and Watts (2009) reported that homophily arises not only from individual preferences but also from structural conditions that create opportunities to meet similar others, such as shared classes or clubs, and that the process amplifies over time. Currarini, Jackson and Pin (2009) used an economic model to explain how the degree of homophily varies with group size. Research such as that of McPherson, Smith-Lovin and Brashears (2006) has also prompted discussion that homophily's influence may grow as core discussion networks shrink.

Methodological issues and significance

A major challenge in network research is determining whether friends who behave alike influenced each other or were connected because they were similar to begin with. Shalizi and Thomas (2011) showed that homophily and social contagion are in principle generically confounded in ordinary observational data. Aral, Muchnik and Sundararajan (2009) reported from data on adoption of an online service that a large share of apparent influence effects may actually reflect homophily. Homophily is used with the strength of weak ties to explain how new information spreads, and with the filter bubble to explain how online polarization emerges.

FAQ

What is homophily in simple terms?: It is the tendency for people to bond with and spend time with others who are similar to them in age, education, tastes or views — the idea behind "birds of a feather flock together."
Are friends similar because of homophily or because they influence each other?: It can be both. People select similar others as friends and also become more alike after becoming friends. Because the two are hard to separate with observational data alone, researchers use experiments and more sophisticated analytic methods.

Sources reviewed: 2026-10-26

References

McPherson, M., Smith-Lovin, L., & Cook, J. M. (2001). Birds of a feather: Homophily in social networks. Annual Review of Sociology, 27, 415–444. The most-cited review of homophily — read this first for the concept and evidence in one place.
Lazarsfeld, P. F., & Merton, R. K. (1954). Friendship as a social process: A substantive and methodological analysis. In M. Berger, T. Abel, & C. H. Page (Eds.), Freedom and Control in Modern Society (pp. 18–66). New York: Van Nostrand. Where the term and the status/value distinction were coined — the conceptual starting point.
Kandel, D. B. (1978). Homophily, selection, and socialization in adolescent friendships. American Journal of Sociology, 84(2), 427–436. Separates selecting similar friends from becoming similar — the selection vs. influence question.
Kossinets, G., & Watts, D. J. (2009). Origins of homophily in an evolving social network. American Journal of Sociology, 115(2), 405–450. Uses university email data to separate individual preference from structural opportunity — homophily's origins, data-driven.
Currarini, S., Jackson, M. O., & Pin, P. (2009). An economic model of friendship: Homophily, minorities, and segregation. Econometrica, 77(4), 1003–1045. An economic model of friendship formation and group size — for the formal, theoretical angle.
Shalizi, C. R., & Thomas, A. C. (2011). Homophily and contagion are generically confounded in observational social network studies. Sociological Methods & Research, 40(2), 211–239. A methodological warning that homophily and contagion are confounded in observational data — essential when reading network studies.
Aral, S., Muchnik, L., & Sundararajan, A. (2009). Distinguishing influence-based contagion from homophily-driven diffusion in dynamic networks. Proceedings of the National Academy of Sciences, 106(51), 21544–21549. Shows how much apparent online influence is really homophily — useful for diffusion and marketing research.
McPherson, M., Smith-Lovin, L., & Brashears, M. E. (2006). Social isolation in America: Changes in core discussion networks over two decades. American Sociological Review, 71(3), 353–375. Tracks changes in Americans' core discussion networks — how homophily plays out in real relationship structures.

Reports and materials that use this theory (Korean)

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This article was last updated on October 27, 2026. It is based on widely recognized original works and textbooks; when citing it in a paper, please check the original sources listed in the references.