Similarity bias (also called affinity bias) is the pull toward people who resemble us in background, interests, style or views, and it can quietly tilt decisions about hiring, promotion and who gets the interesting assignment.

Where it comes from

Psychologist Donn Byrne spent years showing that people like others more when they share their attitudes, a line of work he summarized in 1971.¹ Sociologists later found the same pattern in friendships, advice networks and workplace ties and gave it a name, homophily.² In 2012, Lauren Rivera published a study based on 120 interviews with hiring professionals at elite U.S. investment banks, consulting firms and law firms. Evaluators looked for candidates who shared their leisure pursuits, experiences and ways of presenting themselves, and this often weighed more heavily than productivity alone.³

Where it goes wrong

Similarity feels like "fit," which makes it easy to defend. Rivera is clear that the employers she studied were hiring qualified people; shared culture decided between strong candidates. The trouble starts when "fit" stays undefined, because each evaluator then fills it in with a picture of themselves.

Talent Takeaway

  • Define fit as a short list of behaviors the job requires, such as how someone handles disagreement or picks up a new skill.
  • Score candidates against that list before you notice who you enjoyed talking to.
  • Those of us who develop others do some of our best work with people who think and talk quite differently from us, and every seat we open to someone unlike us widens the circle of people who get to grow.

¹ Byrne, D. (1971). The attraction paradigm. Academic Press.

² McPherson, M., Smith-Lovin, L., & Cook, J. M. (2001). Birds of a feather: Homophily in social networks. Annual Review of Sociology, 27, 415–444.

³ Rivera, L. A. (2012). Hiring as cultural matching: The case of elite professional service firms. American Sociological Review, 77(6), 999–1022.

Further reading: Rivera, L. A. (2015). Pedigree: How elite students get elite jobs. Princeton University Press.