Dunbar's numbers

Dunbar’s 6 Magic Numbers

You might have heard of the (in)famous Dunbar’s number, about the limit of the number of stable relationships we can maintain.

What does Dunbar’s number refer to?

A widespread and popular belief says that humans possess a cognitive capacity limited to keeping track of and maintaining stable relationships with approximately 150 people. This significant number, also known as Dunbar’s number, originates from extrapolating a regression line describing the relationship between relative neocortex size and group size in primates.

This number was first proposed in the 1990s by British anthropologist Robin Dunbar.

Is Dunbar’s number real?

A team of researchers recalculated Dunbar’s number using his original methods and higher volume and quality data. Their estimates went as high as 520 and were stretched over a wide enough range as to be nearly useless. The authors suggest that the original method used to calculate the number of friends a person can have is also theoretically flawed.

The point of this study isn’t to replace Dunbar’s number, but to dismiss the notion that such a number can be determined in the first place. The authors go so far as to end their paper with:

It is our hope, though perhaps futile, that this study will put an end to the use of ‘Dunbar’s number’ within science and in popular media. ‘Dunbar’s number’ is a concept with limited theoretical foundation, lacking empirical support.

However, this number has always been the subject of criticism. An alternative value based on empirical studies of American social groups is a much higher 291, nearly double Dunbar’s original. These studies also suggest that the median social network has 231 persons in it. That value wasn’t figured by crunching other numbers, but it kept coming up repeatedly when the authors of that study looked at the professional and social networks cultivated by different groups of people.

Dunbar’s other numbers

While the magic number above made it into popular media, Dunbar has other numbers, too:

  • 1500: The number of people we can name and recognize
  • 500: The number of not-so-close acquaintances we can keep
  • 150: Our stable relationships (this is one above)
  • 50: People we call friends or would invite to a group dinner
  • 15: The close friends we trust
  • 5: Our best friends and closest support group

Probably also wildly inaccurate, but the order of magnitude and the ratio of decrease is quite interesting. Well, I wish I could name 1500 people…

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