Review of FRIENDS

Dunbar’s number and the science of friendships

Our social networks are vital to who we are as a species. We’re hypersocial compared to nearly any other species. We form close friendships, extended kin and social networks, are relatively friendly to strangers, and navigate complex social webs in nearly every facet of our lives.

But what do we really know about friendships? How many does the average person have? What determines who becomes our friend? How long do friendships last? In Friends: Understanding the Power of our Most Important Relationships, friendship expert, Robin Dunbar provides a comprehensive science account of everything you ever wanted to know about the science of friendships.

Have you ever heard of “Dunbar’s number”? It’s rather famous in science circles, anyway. It’s a number devised by Robin Dunbar himself and it is the statistical average number of actual friends a person has. It’s a number that Dunbar has studied cross-culturally and across various contexts.

A friend is someone whose name you know, along with stuff about them and their family; people you wouldn’t mind talking to in public if you were to see them unplanned. But within this 150 are inclusive “layers” of other friendships: 50 good friends, 15 best friends, and five closest friends, with 1.5 intimate friends (usually a spouse and/or very best friend). Outside that 150-person friend layer? An additional 350 (for a total of 500) acquaintances (think coworkers), and a 1,500-person layer of people’s names you know, but little else. And finally, a layer of 3,000-5,000 faces you know.

Dunbar’s number forms the foundation of Friends, but the book goes beyond the science and meaning of this number to explore all the intricacies of friendships.

How much time we spend with friends (we spend less time with each friend as they move to the outer layers), how much time it takes to make a friend (about 45 hours of time together) and for them to move through to the most inner layers of friendship (an additional 150 hours), and what factors we look for in friends (e.g., language, location, education, hobbies, world view, humor, and music). He explores our most intimate friendships – romantic relationships – and sex-differences in friendships. And after we learn about what makes friendships, we learn why they end.

Friends really is a science world tour of everything there is to know about friendships from a psychological perspective. I also found particularly interesting how consistent these results are cross-culturally, which should be expected as social relationships were foundational to our long evolutionary history as humans. But also that these friendship layers also seem to play out in a decidedly modern context – online!

If you’re curious about friendships, this is a must-read book. It’s quite research heavy in presentation (and pretty long at 360 pages of main text), but written well and on a topic that resonates with everyone who may read it.

Published: April 2022

Publisher: Little, Brown

Format: Hardcover

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If you think this sounds interesting, bookmark these other great reads:

• Artificial Intimacy: Virtual Friends, Digital Lovers, and Algorithmic Matchmakers by Rob Brooks (2021)

• Different: Gender Through the Eyes of a Primatologist by Frans de Waal (2022). Read my review.

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