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Homophily (from Ancient Greek ὁμός (homós) 'same, common', and φιλία (philía) 'friendship, love') is a concept in sociology describing the tendency of individuals to associate and bond with similar others, as in the proverb "birds of a feather flock together".[1] The presence of homophily has been discovered in a vast array of network studies: over 100 studies have observed homophily in some form or another, and they establish that similarity is associated with connection.[2] The categories on which homophily occurs include age, gender, class, and organizational role.[3]

The opposite of homophily is heterophily or intermingling. Individuals in homophilic relationships share common characteristics (beliefs, values, education, etc.) that make communication and relationship formation easier. Homophily between mated pairs in animals has been extensively studied in the field of evolutionary biology, where it is known as assortative mating. Homophily between mated pairs is common within natural animal mating populations.[4]

Homophily has a variety of consequences for social and economic outcomes.[5]

Types and dimensions[edit]

Baseline vs. inbreeding[edit]

To test the relevance of homophily, researchers have distinguished between two types:[2]

  • Baseline homophily: simply the amount of homophily that would be expected by chance given an existing uneven distribution of people with varying characteristics; and
  • Inbreeding homophily: the amount of homophily over and above this expected value, typically due to personal preferences and choices.

Status vs. value[edit]

In their original formulation of homophily, Paul Lazarsfeld and Robert K. Merton (1954) distinguished between status homophily and value homophily, find that individuals with similar social status characteristics are more likely to associate with each other than by chance:[6][2]

  • Status homophily: includes both ascribed characteristics (e.g. race, ethnicity, sex, and age) and acquired characteristics (e.g., religion and education).
  • Value homophily: involves association with others who think in similar ways, regardless of differences in status characteristics.


Race and ethnicity[edit]

Social networks in the United States today are strongly divided by race and ethnicity,[7] which account for a large proportion of inbreeding homophily (though classification by these criteria can be problematic in sociology due to fuzzy boundaries and different definitions of race[8]).

Smaller groups have lower diversity simply due to the number of members. This tends to give racial and ethnic minority groups a higher baseline homophily. Race and ethnicity also correlates with educational attainment and occupation, which further increase baseline homophily.[2]

Sex and gender[edit]

In regard to sex and gender, baseline homophily of networks is relatively low compared to race and ethnicity. Men and women frequently live together, and are both large and equally-sized populations. Most sex homophily is of the inbreeding type.[2] Especially in schools, students tend to have a high gender homophily.[9]


Most age homophily is of the baseline type. An interesting pattern of inbreeding age homophily for groups of different ages was found by Marsden (1988).[10] It indicated a strong relationship between someone's age and the social distance to other people with regard to confiding in someone. For example, the larger age gap someone had, the smaller chances that they were confided by others with lower ages to "discuss important matters."[2]


Homophily based on religion is due to both baseline and inbreeding homophily.[2]

Education, occupation and social class[edit]

Family of birth accounts for considerable baseline homophily with respect to education, occupation, and social class.[2]


Homophily occurs within groups of people that have similar interests as well. We enjoy interacting more with individuals who share similarities with us, so we tend to actively seek out these connections. Additionally, as more users begin to rely on the Internet to find like minded communities for themselves, many examples of niches within social media sites have begun appearing to account for this need. This response has led to the popularity of sites like Reddit in the 2010s, advertising itself as a "home to thousands of communities...and authentic human interaction."[11]

Social media[edit]

As social networks are largely divided by race, social-networking websites like Facebook also foster homophilic atmospheres.[12] When a Facebook user 'likes' or interacts with an article or post of a certain ideology, Facebook continues to show that user posts of that similar ideology (which Facebook believes they will be drawn to). In a research article, McPherson, Smith-Lovin, and Cook (2003) write that homogeneous personal networks result in limited "social worlds in a way that has powerful implications for the information they receive, the attitudes they form, and the interactions they experience."[13] This homophily can foster divides and echo chambers on social networking sites, where people of similar ideologies only interact with each other.

Causes and effects[edit]


Geography: Baseline homophily often arises when the people who are located nearby also have similar characteristics. People are more likely to have contact with those who are geographically closer than those who are distant. Technology such as the telephone, e-mail, and social networks have reduced but not eliminated this effect.

Family ties: Family relationships often produce relatively close, frequent contact among those who are at great geographic distance. These ties tend to decay slowly, but can be dramatically restructured when new marriages occur.

Organizations: School, work, and volunteer activities provide the great majority of non-family ties. Many friendships, confiding relations, and social support ties are formed within voluntary groups. The social homogeneity of most organizations creates a strong baseline homophily in networks that are formed there.[14]

Isomorphic sources: The connections between people who occupy equivalent roles will induce homophily in the system of network ties. This is common in three domains: workplace (e.g., all heads of HR departments will tend to associate with other HR heads), family (e.g., mothers tend to associate with other mothers), and informal networks.

Cognitive processes: People who have demographic similarity tend to own shared knowledge, and therefore they have a greater ease of communication and share cultural tastes, which can also generate homophily.


According to one study, perception of interpersonal similarity improves coordination and increase the expected payoff of interactions, above and beyond the effect of merely "liking others."[15] Another study claims that homophily produces tolerance and cooperation in social spaces.[16] However, homophilic patterns can also restrict access to information or inclusion for minorities.[17]

Nowadays, the restrictive patterns of homophily can be widely seen within social media. This selectiveness within social media networks can be traced back to the origins of Facebook and the transition of users from MySpace to Facebook in the early 2000’s.[18] One study of this shift in a network’s user base from danah boyd (2011) found that this perception of homophily impacted many individuals' preference of one site over another.[19] Most users chose to be more active on the site their friends were on. However, along with the complexities of belongingness, people of similar ages, economic class, and prospective futures (higher education and/or career plans) shared similar reasons for favoring one social media platform. The different features of homophily affected their outlook of each respective site.

The effects of homophily on the diffusion of information and behaviors are also complex. Some studies have claimed that homophily facilitates access information,[20] the diffusion of innovations and behaviors,[21] and the formation of social norms.[22] Other studies, however, highlight mechanisms through which homophily can maintain disagreement, exacerbate polarization of opinions, lead to self segregation between groups, and slow the formation of an overall consensus.[23][24]

As online users have a degree of power to form and dictate the environment, the effects of homophily continue to persist. On Twitter, terms such as “Stan Twitter”, “Black Twitter”, or “Local Twitter”[25] have also been created and popularized by users to separate themselves based on specific dimensions.

Homophily is a cause of homogamy—marriage between people with similar characteristics.[26] Homophily is a fertility factor; an increased fertility is seen in people with a tendency to seek acquaintance among those with common characteristics.[27] Governmental family policies have a decreased influence on fertility rates in such populations.[27]

See also[edit]


  1. ^ Ferguson, Niall (August 15, 2017). "The False Prophecy of Hyperconnection". Foreign Affairs. Retrieved October 1, 2017. At the same time, birds of a feather flock together. Because of the phenomenon known as "homophily", or attraction to similarity, social networks tend to form clusters of nodes with similar properties or attitudes.
  2. ^ a b c d e f g h McPherson, M.; Smith-Lovin, L.; Cook, J. M. (2001). "Birds of a Feather: Homophily in Social Networks". Annual Review of Sociology. 27: 415–444. doi:10.1146/annurev.soc.27.1.415.
  3. ^ Retica, Aaron (10 December 2006). "Homophily". New York Times.
  4. ^ Jiang, Yuexin; Bolnick, Daniel I.; Kirkpatrick, Mark (June 2013). "Assortative Mating in Animals". The American Naturalist. 181 (6): E125–38. doi:10.1086/670160. hdl:2152/31270. JSTOR 10.1086/670160. PMID 23669548. S2CID 14484725.
  5. ^ Jackson, Matthew O. (2010-11-01). Social and Economic Networks. Princeton University Press. doi:10.2307/j.ctvcm4gh1. ISBN 978-1-4008-3399-3. JSTOR j.ctvcm4gh1.
  6. ^ Lazarsfeld, Paul F., and Merton, Robert K. 1954. "Friendship as a Social Process: A Substantive and Methodological Analysis." Pp. 18–66 in Freedom and Control in Modern Society, edited by M. Berger, T. Abel, and C. H. Page. New York: Van Nostrand.
  7. ^ Moody, James (November 2001). "Race, School Integration, and Friendship Segregation in America". American Journal of Sociology. 107 (3): 679–716. doi:10.1086/338954. ISSN 0002-9602. S2CID 145265678.
  8. ^ Deaux, Kay (2018-05-01). "Ethnic/Racial Identity: Fuzzy Categories and Shifting Positions". The Annals of the American Academy of Political and Social Science. 677 (1): 39–47. doi:10.1177/0002716218754834. ISSN 0002-7162. S2CID 149999583.
  9. ^ Shrum, Wesley; Cheek, Neil H.; Hunter, Saundra MacD. (October 1988). "Friendship in School: Gender and Racial Homophily". Sociology of Education. 61 (4): 227. doi:10.2307/2112441. ISSN 0038-0407. JSTOR 2112441.
  10. ^ Marsden, P. V. 1988. "Homogeneity in confiding relations." Social Networks 10:57–76.
  11. ^ "Homepage - Reddit". www.redditinc.com. Retrieved 2020-10-10.
  12. ^ Aiello, Luca Maria; Barrat, Alain; Schifanella, Rossano; Cattuto, Ciro; Markines, Benjamin; Menczer, Filippo (2012-05-01). "Friendship prediction and homophily in social media". ACM Transactions on the Web. 6 (2): 1–33. doi:10.1145/2180861.2180866. ISSN 1559-1131. S2CID 12761051.
  13. ^ McPherson, Miller; Smith-Lovin, Lynn; Cook, James M. (2003-11-28). "Birds of a Feather: Homophily in Social Networks". Annual Review of Sociology. 27 (1): 415–444. doi:10.1146/annurev.soc.27.1.415.
  14. ^ Chancellor, J.; Layous, K.; Margolis, S.; Lyubomirsky, S. (2017). "APA PsycNet". Emotion. 17 (8): 1166–1180. doi:10.1037/emo0000311. PMID 28358560. S2CID 14600185. Retrieved 2021-10-02.
  15. ^ Chierchia, Gabriele; Coricelli, Giorgio (2015). "The impact of perceived similarity on tacit coordination: propensity for matching and aversion to decoupling choices". Frontiers in Behavioral Neuroscience. 9: 202. doi:10.3389/fnbeh.2015.00202. PMC 4516978. PMID 26283940.
  16. ^ Mark, N. P. (2003). "Culture and competition: Homophily and distancing explanations for cultural niches". American Sociological Review. 68 (3): 319–345. doi:10.2307/1519727. JSTOR 1519727.
  17. ^ Karimi, Fariba; Génois, Mathieu; Wagner, Claudia; Singer, Philipp; Strohmaier, Markus (2018-07-23). "Homophily influences ranking of minorities in social networks". Scientific Reports. 8 (1): 11077. Bibcode:2018NatSR...811077K. doi:10.1038/s41598-018-29405-7. ISSN 2045-2322. PMC 6056555. PMID 30038426.
  18. ^ Tancer, Bill (2007-10-24). Time. ISSN 0040-781X http://content.time.com/time/business/article/0,8599,1675244,00.html. Retrieved 2020-10-10. Missing or empty |title= (help)
  19. ^ "White Flight in Networked Public? How Race and Class Shaped American Teen Engagement with MySpace and Facebook" (PDF).
  20. ^ Choudhury, M. D (2010). ""Birds of a feather": Does user homophily impact information diffusion in social media". arXiv:1006.1702 [cs.CY].
  21. ^ Christakis, N. A; Fowler, J. H. (2007). "The spread of obesity in a large social network over 32 years" (PDF). The New England Journal of Medicine. 357 (4): 370–379. CiteSeerX doi:10.1056/nejmsa066082. PMID 17652652.
  22. ^ Centola, D; R, Willer; M, Macy (2005). "The emperor's dilemma: A computational model of self-enforcing norms". American Journal of Sociology. 110 (4): 1009–1040. doi:10.1086/427321. JSTOR 10.1086/427321. S2CID 18831420.
  23. ^ Golub, Benjamin; Jackson, Matthew O. (2012-07-26). "How Homophily Affects the Speed of Learning and Best-Response Dynamics". The Quarterly Journal of Economics. Oxford University Press (OUP). 127 (3): 1287–1338. doi:10.1093/qje/qjs021. ISSN 0033-5533.
  24. ^ Centola D, Gonzalez-Avella JC, Eguiluz VM, San Miguel M. (2007). "Homophily, cultural drift, and the co-evolution of cultural groups". Journal of Conflict Resolution. 51 (6): 905–29. arXiv:physics/0609213. doi:10.1177/0022002707307632. S2CID 17351007.CS1 maint: multiple names: authors list (link)
  25. ^ Lorenz, Taylor (2018-07-03). "How Twitter Became Home to the Teen Status Update". The Atlantic. Retrieved 2020-10-10.
  26. ^ Fiore, A. T. and Donath, J. S. (2005). "Homophily in Online Dating: When Do You Like Someone Like Yourself?". MIT Media Lab.
  27. ^ a b Thomas Fent; Belinda Aparicio Diaz; Alexia Prskawetz (2013). "Family policies in the context of low fertility and social structure". Demographic Research. 29 (37).