The evolutionary psychologist Robin Dunbar calculated that humans can maintain relationships with about 150 people at a time. But that number varies depending on the strength of the relationships, according to the forthcoming book, The Start-Up of You: Adapt to the Future, by LinkedIn cofounder Reid Hoffman and entrepreneur-author Ben Casnocha. The book is due out Feb. 14, and portions of it appeared in the Feb. 6 edition of Fortune.
It was the excerpt on Dunbar’s Number that caught our eye:
“Just as a digital camera cannot store an infinite number of photos and videos, you cannot maintain an infinite number of allies or acquaintances. The maximum number of relationships we can realistically manage — the number that can fit on the memory card, as it were — is described as Dunbar’s Number, after the evolutionary psychologist Robin Dunbar. In the early 1990s, Dunbar studied the social connections within groups of monkeys and apes. He theorized that the maximum size of their overall social group was limited by the small size of their neocortex. Based on our neocortex size, Dunbar calculated that humans should be able to maintain relationships with roughly 150 people at a time. He also found that many businesses and military groups organize their people into cliques of about 150. Hence, Dunbar’s Number of 150.”
All well and good. But where the excerpt gets really interesting is when the authors apply an analogy to Dunbar’s Number:
“There is indeed a limit to the number of relationships you can maintain, but a crucial qualifier is that there is not one blunt limit of 150; in fact, there are different limits for different types of relationships. Think back to the digital camera. Either you can take low-resolution photographs and store 100 of them in total, or you can take high-resolution photographs and store 40. In relationships, you may have only a few close buddies you see every day, yet you can stay in touch with many distant friends if you e-mail them only once or twice a year. But there’s a twist: You can actually maintain a much broader social network than the people you currently ‘know.’”
Fascinating, but how can you use this info? Thankfully, the authors offer a possible means for mining your low-res relationships: recruiting. “Weak ties in a career context,” they write, “were formally researched in 1973, when sociologist Mark Granovetter asked a random sample of professionals how they had found their new job. It turns out that 82% of them found their position through a contact they saw only occasionally or rarely. In other words, the contacts who referred jobs were ‘weak ties.’”
For more on Granovetter and the research behind The Start-up of You, see the “plus” section, below.
It was in 1982 that Stanford Professor Mark Granovetter wrote The Strength of Weak Ties: A Network Theory Revisited. To their credit, authors Hoffman and Casnocha have created a web page where you can find links to all the sociological studies cited in their book, including Granovetter's. And if you liked Granovetter's study about the power of weak ties, then you'll really appreciate Rutgers professor Daniel Z. Levin's research on dormant ties, a synopsis of which appeared in the inaugural edition of Build.