What is Dunbar’s Number?

Dunbar’s Number, proposed by British Anthropologist Robin Dunbar, measures the “cognitive limit to the number of individuals with whom any one person can maintain stable relationships”.

The number, which approximates to 150, would seem to have important implications for social design.

1. It suggests that there is an upper-limit to the number of meaningful relationships we can cultivate, either online or off. Most likely the number would be different for everyone, but at least acknowledging a limit can be healthy because it keeps down pie-in-the-sky visions of what people do. It’s always good to remember that we have limits.
2. It suggests that a lot of the activity on social sites isn’t really about “stable relationships”. It should be clear, but isn’t always, that 845 connections on LinkedIn aren’t really friends or even associates. Most of the social ties, if they even exist, are much looser than that. So though the number is high, it might not mean that the person is well-connected more than it means they’re hungry for a high number of connections. So Dunbar’s number, even if it is off by 100, is yet more indication that the social relationships on sites aren’t what they always appear to be. The question becomes: what kind of relationships are they?

Dunbar came up with the number after studying other primates and then applying that knowledge to humans. He verified it, so to speak, by analyzing the number of people in various social groups around the world and in different situations. For example, he found the size of certain tribal villages to be about 150.

Similar to the Magical Number 7, it would be easy to misapply Dunbar’s Number. For example, I can imagine systems being built to allow only a certain number of contacts, for example. That’s an extreme case, but given what extremes people go to stick to numbers it wouldn’t surprise me.

Nevertheless, Dunbar’s Number might be good to keep in the back of the mind in order to stay reasonable.