What is the Dunbar number; who discovered?

Robin Dunbar, a British anthropologist, and professor at Oxford University, developed a theory in 1992 within the scope of the "Lucy to Language" project, which was initiated on the occasion of the centennial of the British Academy. To test it, he examines the social relationships of monkeys among themselves. According to research conducted by Robin Dunbar in collaboration with scientists from the universities of Liverpool, Manchester, and Edinburgh, we need to have a set of cognitive skills in order to maintain our friendships. However, the word "friend" refers to people with whom we are in a friendly relationship rather than acquaintances. These cognitive abilities, also referred to as "mind reading" by social scientists, express the capacity to understand what another person is thinking. This allows us to demonstrate behaviors that help us cope with our complex social world, including being able to chat with people. This research suggested for the first time that superiority in these skills is related to the size of some key areas of the brain, particularly the frontal lobe.

Dunbar's number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships—relationships in which an individual knows who each person is and how each person relates to every other person. This number was first proposed in the 1990s by British anthropologist Robin Dunbar, who found a correlation between primate brain size and average social group size.

Researchers at the Magnetic Resonance and Image Analysis Research Center at the University of Liverpool took anatomical MRI images of the brains of 40 volunteers and measured the size of their prefrontal cortex, a brain region involved in higher-order thinking. Participants were then asked to rank everyone they had contact with socially rather than professionally in the past seven days. Participants also took a test that determined their mind-reading skills.

Robin Dunbar says that those who have more friends and do better on the mind-reading test have more nerve volume in the region of the orbital frontal cortex, the part of the forebrain located above the eyes. Understanding such a link between an individual's brain size and the number of friends contributes to understanding the mechanisms behind why humans' brains are larger than those of other primate species. The frontal lobe of the human brain has grown dramatically, especially in the last half million years.

As a result, Dunbar finds that the human neocortex can only develop meaningful relationships with a certain number of people. He says that this number is "150" in underdeveloped regions as well as in big cities. That's why this number is called the "Dunbar Number". The research reveals evidence that there is a link between the number of friends and the size of the brain's orbital prefrontal cortex. Accordingly, this region of the brain is larger in people with many friends. The results of the research were published in the journal Proceedings of the Royal Society B.

When we look at our relationship style among the 150 people who make up our social world, some patterns emerge. In the first place, there are our closest people, those who are with us in difficult times, those we can never give up, these usually do not exceed 3-5 people. Above this core group is another group, usually around 10 people, with whom we are more distant. This group is called the "sympathy group" by social psychologists, above it is another circle of 30 or more people. When we look at the numbers that make up all these circles, although a pattern does not stand out, when we consider the circles to include each other, we witness that they increase by tripling. While we can't be entirely sure why these circles are increasing by a factor of three, research shows that each of these circles of acquaintances is in tune with the way we connect with the people who make up those circles. For example, we communicate with the inner circle of five people at least once a week, with a group of 15 people at least once a month, and with 150 people at least once a year. With those who remain above this number, maybe we only say hello once. Dunbar says that we spend 40% of our social time on the 5 closest people and 20% on the 10 people we feel close to.

Researcher Dr. Joanne Powell, from the Department of Psychology at the University of Liverpool, says that perhaps the most important finding of their research is that the relationship between brain size and social network size is associated with "mind reading" skills. Powell adds that this means that the size of our brains determines our social skills and that it is possible for us to have a large number of friends. Robin Dunbar states that the volunteers participating in the research are generally graduate students of similar ages and potentially similar social activity opportunities. According to Dunbar, although leisure time, geography, personality, and gender are all factors that affect friendship, we also know that some of these factors, especially gender, are also related to mind-reading skills. Dunbar emphasizes that their studies show a link between understanding what other people think and social network size.

Although the number 150 is suitable for people over a certain age today; difficult for young people. Especially when we consider the different platforms of social media. However, according to Dunbar, the reason why this number is not higher is related to our genes. This number is a function of the size of the human brain's neocortex. This number is the neurological limit for maintaining healthy and equitable relationships in a social group. Once this limit is crossed, people's social attachment to each other becomes unsustainable as they can no longer conceptualize each other as human beings. As a result of crossing the border, things can no longer function without hierarchy and social roles. Laws, rules, and norms are needed to keep these groups together. All this happens because the human brain did not evolve in large groups, but rather in small groups where it communicated face-to-face.

When Dunbar looks for the application of the number 150 in anthropology, when he examines 21 different hunter-gatherer societies about which we have precise information, he finds that this number is 148.4 people. Today, the Hutterites and Amish living in North America are in groups of 110 people on average. When the number of group members exceeds 150, they split the group. They show the reason for this as the alienation of people from each other when the number is exceeded.

Another example is that in organizations with less than 150 employees, there are basically fewer problems in mutual relations; When this number grows, a formal hierarchy is needed in order to be able to work efficiently.

The Dunbar number was tested on social media in 2011 by a study conducted by Bruno Goncalves, Nicola Perra, and Alessandro Vespignani. In this research based on Twitter, people's Twitter interactions were studied for four years. As a result, it was found that people only had meaningful interactions with “150” people, regardless of the number of followers.

It is seen that; There is a limit to the number of people we can keep at a certain level of intimacy. The Dunbar number shows us that a significant portion of our relationships is either passive or unproductive. When a new person enters your life, someone has to go to the next level to make room for them.