Why we can’t have more than 150 friends and still need more than that

Everyone’s talking about “social”: “social networks”, “social media”, “social web”, “social games”, “social apps”, social everything, increasingly culminating in the idea of “social business”. But what does it mean to be social in this context? Are you more social when you have 1,000 followers on Twitter or Facebook rather than just 100? It certainly seems that way when looking at many social media success stories.  However, can you actually be social with 1,000 or more people? Robin Dunbar, Professor of Evolutionary Anthropology at the University of Oxford,  believes that the cognitive limit to the number of individuals humans can maintain social relationships with is at 150. Much to the professor’s surprise, “Dunbar’s number” has made a considerable career on the Internet, certainly helped by the popularization of his findings through Malcolm Gladwell’s book “Tipping Point” and supporters such as marketing guru Seth Godin. Still, Dunbar’s number is not yet common knowledge, and among those who know it, it’s meaning is controversial. So, I figured it’s worth looking into the concept and its possible applications for business communications.

Based on studies with primates showing that there is a correlation between the size of their social groups and the size of their brain’s neocortex, Dunbar speculated in a 1992 paper that this correlation could be extrapolated to humans and predicted a group size of approx. 150. He then compared this number with data on social group sizes in human history such as the sizes of villages, tribes or units in ancient armies and found his hypothesis confirmed (within a band of variation). In a 2002 study, he also examined the “social network size in contemporary Western society based on the exchange of Christmas cards”, and again,  the “maximum network size averaged 153.5 individuals, with a mean network size of 124.9”.

If 150 is indeed the maximum of stable inter-personal relationships humans can maintain, Dunbar’s number also explains why larger groups don’t work without additional structures such as hierarchies or laws to organize the relationships. This is what Malcolm Gladwell picked up on pointing out that organizations suffer from a sharp productivity loss when growing larger than 150 employees. As a result, companies such as Gore, the manufacturer of Gore-Tex fabrics, organized their teams in smaller groups, so that they could keep strong working relationships.

Social GroomingFinally, managing more than 150 stable relationships would not only go beyond the brain’s capacity but also take too much time. In that regard, humans face the same challenge as primates: social grooming is laborious! It has been suggested, though, that humans might be able to increase the number of relationships with the help of social media, since it makes it easier to memorize a relation’s origin and then stay in touch, even over large distances. Dunbar counters, though, that dependable relationships need in-person meetings and social media still doesn’t remove the biological constraints (see for instance this video interview Dunbar had with the Guardian). And indeed, a recent study by Gonçalves, Perra and Vespignani (August 2011) validated Dunbar’s argument. They modeled activity of 1.7 m users on Twitter over six months and found “the data in agreement with Dunbar’s result; users can entertain a maximum of 100-200 stable relationships.”

Does this mean any number of social network connections larger than 150 doesn’t make sense? Well, it depends on what you are trying to achieve.  For instance, a mobile social network company called Path limited the number of friends users can have on their network to 150 (with reference to Dunbar), since their service is built for circles of close friends. That’s understandable. However, as early as 1973, sociologist Mark Granovetter pointed out that not only those people you are closely connected with are important for your network. In fact, they might even bring less value to it, because they probably know the same people and things that you do whereas your wider network of weak ties might open up access to new information and new networks. On a larger scale, the component of weak ties supports the concept of crowdsourcing as famously crafted by James Surowiecki back in 2004: If you really want to extract the wisdom of crowds, diversity is one of the critical success factors, and you will only get it out of a wide network with weak ties.

So, from my perspective, Dunbar’s number is certainly a factor business communicators have to take into consideration. If you want to have a group of people interact and collaborate productively to get things done, the size of this group shouldn’t go beyond Dunbar’s number. Making this group larger might lead to a loss in productivity, because an increasing amount of “noise” in the system can be distracting and will increase the need for coordination and filtering. Also, large numbers of followers or “fans” shouldn’t be mistaken as a proof of social interaction that is by default allowing for stronger relationships than traditional reach. Dunbar has shown that stable interpersonal relationships can’t be managed in large numbers, unless you do it one Dunbar group at a time. IBM employees, for example, operate thousands of internal and external social media platforms creating tens of thousands strong ties inside the organization and outside-in.

Conversely, if the goal is to open up a specific business unit or the whole organization to innovation, it is necessary to go far beyond the Dunbar number and include weak ties. In fact, too many strong relationships within the crowd you are working with will threaten the diversity needed to go beyond existing approaches. Online communities in particular are threatened by the “echo chamber effect“, because once a claim is made by one participant it’s extremely easy to have it repeated by like-minded people, resulting into the reinforcement of their beliefs and possibly hindering critical discourse. Memes or myths  are being created as a result and can block the way for innovation. In addition, the echo chamber effect can be aggravated by algorithms homogenizing search results within social networks, a phenomenon Eli Pariser called the filter bubble. In fact, I sometimes do have the impression that we as business communicators do suffer from the echo chamber in our social networks, because a Dunbar group is reinforcing myths such as  the loss of control on the social web at conferences and on the web. Thanks to Dunbar and others, we can better understand these mechanisms. It is a whole different discussion how to create a wide network with weak ties allowing for diversity and then aggregate the ideas for innovation. Perhaps, a discussion for another post. This one has already been long enough!

Georg Kolb


14 thoughts on “Why we can’t have more than 150 friends and still need more than that

  1. This post, like many texts about Dunbar’s number, repeats the same mistake that I see in lots of places, when it comes to these 150. People look at Dunbar’s research, then they look at Facebook etc., and then say: “See! It makes no sense to have all these friends, you can only deal with 150!”

    And that is absolutely nonsensical, of course. Because Dunbar made his calculations based on observing the lives of simple tribes and primates. And these groups naturally do not have the computing / memory power that we have available today. Someone sitting in the jungle somewhere will indeed have a hard time keeping track of more than 150 people.

    But we don’t, of course! If you make a conscious effort to use the computer, and the social media platform’s memory help, you can absolutely increase your number. That is what our work at trnd is based on, and that is what — surprisingly — lots of people who quote Dunbar seem to ignore.

    It’s like saying “A normal person cannot go faster than 25 km/h, so a bicycle makes no sense at all.”

  2. Many thanks for your comment Martin. I was a bit surprised, though, because what I said is not as simple as you seem to believe.
    I did not say it doesn’t make sense to have more than 150 friends. What I said is that it actually depends on what you are trying to achieve. Dunbar’s number relates to groups with strong ties between their members. You need these strong ties, if you want to work closely in smaller groups. However, if you want to gain collective intelligence you do need very large groups with weak ties between their members, so they won’t be Dunbar groups anymore as a result.
    By the way, Dunbar did not only work with primates and tribes, he also did some research with contemporaries, such as the Christmas card experiment. And there were network analysts, confirming that Dunbar’s number was also true on Twitter. I mentioned both.

  3. Hey Georg,

    In the opening paragraph you question if it is possible to be social with a 1000 or more people, I was just curious what you mean exactly by the word “social” in this question. Are you referring to the term social as be “friends” with a 1000 or more people? I know social is a very broad term and has a variety of different meanings and definitions. When I think of being social with people I think of every day social interactions we have with people in which we have 100s of on a daily basis with a large magnitude different people, people we are social with but might not become friends with necessarily. With this definition yes we easily surpass a 1000 people in a week. Isn’t this why social skills are so important especially in the business world? I was just wondering if you could clarify what definition of social your referring too here exactly, thanks.

  4. Thanks for your comment Zach! You are right, the number depends on the defintion of “social”. Dunbar thinks of social relationships with strong ties, meaning that everyone in the social network knows everyone else without introduction. If you want to maintain an ideal network like this, you will struggle to get beyond Dunbar’s number.
    However, you can also have social relationships with weak ties, for instance with thousands of followers you might have on Twitter. The Dunbar network is great for close teamwork, a large network with weak ties is great for innovation in the sense of the “wisdom of crowds”. So, you just need to match the quality of your network with the goal you want to achieve, and that’s what I tried to explain in my post.

  5. Thanks for your fast reply Georg! Just to confirm the “social” you are discussing is in terms of social relationships or friends where Dunbars number applies and is involved in limited strong ties, not the “social” definition in terms of the unbounded number of every day social interactions we have with different people correct?

  6. In this post, I actually covered both: networks with strong and networks with weak ties. Both have their strengths and weaknesses. A Dunbar network is great for tight teamwork, but it can suffer from the bubble or echo chamber effect. People in a network with strong ties tend to confirm each others opinions. So, if you want to get fresh perspectives, it might be better to tap into a large network with weak ties, ideally with heterogeneous members.
    Everyday social interactions are yet another topic, They include interactions with strong ties (such as in your family or your team at work) and weak ties (such as random encounters on the subway).

  7. When you describe “weak ties” in everyday social interactions are you including the remainder of social interactions we have with people throughout the course of our day that might not necessarily be with a weak tie(acquaintances) or strong tie(family, friends)? Like you mentioned random encounters with people on the bus or any other interactions, conversations we have.

  8. No, I didn’t include our everyday social interactions, since the view on this blog was on corporate communications.

  9. But I was asking In everyday social interactions can we be social with everyone we come across, not just strong ties and weak ties but everyone we interact with on a daily basis? Thanks Georg final question

  10. Georg, is there anyway you can answer my final question up above? Thanks, Zach.

  11. I’m not a social scientist, but I would argue that we not only can, but actually are social with everyone we share a social system with. Think of systems such as states, religions cultures, any community really. I’m inclined to say every human can be social with any other human, but then again, sadly, there are human beings who would deny that. So, yes, we should be able to be social with every human we come across, and in most instances we are, at least when we live in a society that isn’t broken.

  12. Is the reason some people deny this because of social and cultural issues such as race discrimination , gender discrimination, different ethnic backgrounds, dehumanization that then in turn drives them not to be social with someone because of these reasons?

  13. So in summary we have the ability and capacity to be social with anyone but unfortunately some people think we can’t be social with certain people because of reasons like biases and discrimination, etc. which is technically false we have the ability. Is this correct? Thanks Georg that will be it.

  14. Is there anyway you answer my previous question. Thanks Georg it’s for research, promise last question. Thanks for all your help.


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