Have you ever heard of Dunbar’s number? This is the number proposed by psychologist, anthropologist and biologist Robin Dunbar to allude to the number of people we usually relate to.
What are its origins and how does it relate to our ancestors and primates? And with the cerebral neoscort? In this article, we’ll answer all of these questions and also explain how Dunbar’s number relates to religious congregations, according to a recent study.
- Related article: “What is social psychology?”
What’s the Dunbar number?
The Dunbar Number is an issue published over 25 years ago by British psychologist, anthropologist and biologist Robin Dunbar (full name Robin Ian MacDonald Dunbar). It consists of the number of people we usually interact with, which is around 150.
According to Dunbar, this number is related to the size of our brain neoscort and its processing capacity. Remember that the cerebral neocortex (or neocortex) is the area of the brain that allows us to reason and think logically and consciously. In other words, it captures our higher mental functions and enables the functioning of executive functions.
Social brain hypothesis
Dunbar’s number is part of the Social Brain Hypothesis, also developed by Robin Dunbar, that there is a correlation between the size of the brain (in particular, the neo-cerebral cortex) and the number of social relationships we can make between people (Although this also applies to primates, as we will see later).
It is a number that has aroused a lot of curiosity in various fields and sciences, such as sociology and anthropology, but also other more “numbered” sciences, such as business administration and statistics.
Origin of this concept in the work of Robin Dunbar
What is the origin of the Dunbar number? Many years ago, primatologists (i.e., professionals who study the behavior of primates) observed the following: Primates have a highly social nature, which causes them to maintain (and have need) social contact with other members of your group.
But not only did they observe this, but in addition, they found that the number of group members with whom the primates maintained social contact was directly related to the volume of their brain neoscort. In other words, they determined that it exists an index of social group size in each species of primate, which differs from one to another according to the volume of the neocortex of each of them.
A few years later, in 1992, Robin Dunbar used the correlation that had been determined in nonhuman primates to predict the size of the social group in humans (i.e. he applied Dunbar’s number humans).
Specifically, Dunbar determined the Dunbar number in humans to be the size of 147.8 (which is usually rounded to 150), although Dunbar clarified that this was an approximate value.
Findings in human societies
The cerebral neoscort is an area of the brain that developed approximately 250,000 years ago. Dunbar began to research different nomadic societies, tribes and villages, to find the Dunbar number of each..
Thus, he studied the size of the social groups of all these societies, and found that the Dunbar number could be classified into three categories: from 30 to 50 people, from 100 to 200 and from 500 to 2,500.
As for his findings and observations, he also warned that a group of 150 people needed a very strong motivation to stay together.
In this sense, Dunbar concluded that in order for a group of this size to remain united and cohesive, its members had to invest at least 42% of their time in socializing with other members of the group.
Which groups have reached Dunbar’s number?
Dunbar also found that only groups or societies that were under great pressure to survive or had a very strong need (such as some nomadic tribes, subsistence peoples, and various military groups) could reach Dunbar’s number.
In addition, he found that these people were almost always in physical contact (or at least close to each other). In contrast, dispersed groups (whose members were not physically close) had fewer ties, fewer ties.
The importance of language
Dunbar not only studied the importance of socialization and needs in explaining Dunbar’s number, but also the importance and power of language. According to him, this could have emerged as a tool to facilitate socializations. This, in turn, could improve cooperation, production, survival …
Thus, language is a tool for cohesion in societies which in turn reduces the need to be in intimate contact with others, both physically and socially.
Relationship with religious communities
A recent (2020) article by Bretherton and Dunbar, relates Dunbar’s number to religion; specifically, with the church growth literature. Thus, this study reveals that Dunbar’s number could also be applied to the size and growth of religious communities.
The study goes a step further and also analyzes other aspects surrounding Dunbar’s famous number; More specifically, the researchers made the following findings or conclusions:
On the one hand, they found that larger congregations have less active participation from each of their members. On the other hand, and this has a lot to do with Dunbar’s number, congregations that have only one leader typically have a participant count of around 150.
In addition, these congregations (with 150 members) are stratified into even smaller functional or social groups.
But what about congregations with more than 150 members? Researchers have revealed that they are suffering major internal tensions leading them to have to reorganize internally. These same congregations (of more than 150 members), in fact, need structural subdivisions so that the active participation of their members takes place.
The article, very interesting to read, essentially provides a theoretical framework that unifies the observations of the literature on church growth, alongside the social brain hypothesis and Dunbar’s number.
- Bretherton, R. and Dunbar, R. (2020). Dunbar’s issue goes to Church: The Social Brain Hypothesis as the third line in the study of Church growth. International Association for the Psychology of Religion.
- Dunbar, R. (1988). Primate social systems. Chapman Hall and Yale University Press.
- Dunbar, R. (1992). Neocortex size as a restriction on group size in primates. Journal of Human Evolution 22 (6): 469-493.
- Dunbar, R. (1993). Co-evolution of neocortex size, group size and tongue in humans. Behavioral and Brain Sciences 16: 681-735.