Dunbar number

Hello! In this article we take a closer look at the Dunbar number, a mythical value that is supposed to estimate how many connections the human can have.

Researchers imply that there is a cognitive limit on the number of relationships for any person. Is it a “natural” parameter or obtained? What factors influence the Dunbar number? And how can we describe our relationships with it? Here, we talk about the Dunbar number and attempt to clarify a few important questions related to its impact.

Introduction to the Dunbar number

The core of Robin Dunbar's, a British anthropologist, original study [1] is testing the relation between the brain’s neocortex volume and the size of the social group for primates.Neocortex is responsible for the higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language. Social group size means the number all dyadic (pair) relationships that the individual of particular species has. To define a “relationship” between two primates, R. Dunbar used the possible foraging parties (whom the individual interacted with to gain food).

The author took data on theaverage size of social group for each of 38 categories* of animals from the primate-like family. The researcher then plotted the average group size against the neocortex volume ratio of the respectable primates’ category.  As a result, R. Dunbar observed the statistically meaningful correlation (r^2 = 0.764 with P<0.001) between these two variables**.

Now, for the main inference of this study which makes it drastically relevant to the topic of building relations. As the next step, R. Dunbar suggested to use that linear dependence between neocortex size and social group volume to infer the size of communities for homo sapiens, ourselves.

Dunbar number questions and answers

What is the Dunbar number ontologically?

The most important thing to recognize about the Dunbar number: it is an average number of connections for the sample from a particular species. The metric was invented by a human to characterize how capable the species is in building relations. It should rather be used to compare the social capabilities of different species (humans and monkeys). But it shouldn’t be applied as an exact limit universally.

So, is the “Dunbar number” just a single value related to species?

Yes, it is a statistical metric indicating how many connections on average individuals belonging to the species have.

Does the Dunbar number vary from person to person?

Yes. Recent reconstruction [3] of Dunbar’s analysis method suggests that, based on neocortex volume estimation, the number of connections may vary between 2 and 336 (95% confidence interval). Hence, the number of connections varies significantly even within the single species. Although, for a particular person, there can be a specific number of relationships they are comfortable dealing with.

Is it innate and constant through life?

Probably not. The Dunbar himself considers several models of cognitive resource requirements for relationship building [1]. The author of the current article doesn’t know yet whether the Dunbar number changes over time, but common sense implies that happens. Factors that might affect the connections limit change are the environment, occupation, attention from others, and relationship type.

What can the Dunbar number say about building relationships?

There are a few ways how the notion of the Dunbar number can help you manage your relationships. Assess how many people you are comfortable keeping in touch with. Then, obtain insights on your relationship-building habits.

First, your “Dunbar number” can tell you what format of relationships is more relevant for you. Do you maintain the narrow circle of tight ties? Do you tend to spend a little bit of time with various people? Or, you are able to mix these approaches?Being aware of your interpersonal relations habits, you can more clearly communicate them to others. That helps build more trustful and predictable relations.

Second, minding the Dunbar limits of your network, you can estimate how much time and heart you have for new people. That empowers casual time management. Can you promise a new mate to hang out on the weekend if there are already several people who might affect the plans?

Third, and the most tricky, reason is that one can move people between circles, knowing the self-capacity at each level. If you think a person can have a greater impact on your life, bring them closer. Or increase distance if maintaining the relationship incurs too much expense.

Bonus: on the memeness of Dunbar number (the author’s view)

Here, we use the “memeness” as a quality to be remembered well, meaning that the discussion around the Dunbar number goes on being kept up by the author himself and other researchers.

As the original Dunbar’s study and subsequent “deconstructions” show, there is no exact limit on how many relationships one can maintain. Then, why has the Dunbar number engaged the minds of researchers and relationship management enthusiasts for more than 30 years?

We think this is about the idea. The mere idea that there is a universal limit on the number of our connections. It sounds really attractive. This is like a determinative law of nature that tells a lot about humanity as a kind. Hence, it is a very tempting challenge to try to measure such a “fundamental” biological constant as a researcher.

Second, the Dunbar number is the domain’s assembly point. Every researcher tipping into the human networks structure wouldn’t pass by the studies of a connections' limit. And the Dunbar’s number, as the early and the most popular among such ideas, would be almost certainly featured. For example, the original Dunbar’s study has been cited 3600+ times, according to Google Scholar. That’s a huge number of citations for every domain.

And the last, the “Dunbar number” is a rememberable word combination! Had it not been given a sound name, the concept itself would not be so tenacious in the mass media.

Conclusion

In conclusion, it doesn’t matter whether the particular value of Dunbar’s number is legit or not. Its main impact lies in the fact that the idea keeps provoking and uniting the researchers around the world. And the subsequent studies inspired by the R. Dunbar's idea help us understand interpersonal relations better.

* Technically, groups studied by Dunbar were neither “categories” nor “species” but “genera” (genus — rank or level of biological classification between family and species). But we will use the word “species” or “category” for simplicity.
** That means that the chance of variable “falling” around this trend line purely by random is less than 0.001%. So, that indicates that the result is non-random. But the actual goodness of that fit (line slope) may not be this reliable.

References

1. R.I.M. Dunbar, Neocortex size as a constraint on group size in primates, Journal of Human Evolution, Volume 22, Issue 6, 1992, Pages 469-493, ISSN 0047-2484, https://www.sciencedirect.com/science/article/abs/pii/004724849290081J
2. Wikipedia - Neocortex https://en.wikipedia.org/wiki/Neocortex
3. Lindenfors Patrik, Wartel Andreas and Lind Johan, ‘Dunbar's number’ deconstructed, 2021, Biol. Lett.1720210158 https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2021.0158
4. https://oxsci.org/end-of-dunbars-number