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Dunbar's number and why it is important for hospitality design.

The Science of Social Limits: How Dunbar's Number Shapes Human Connection and Design.

Dunbar's number and why it is important for hospitality design. Vintage illustration with "Dunbar's Number and Why It is Important for Hospitality Design" text overlay. Features ornate borders and figure.
 

Human connection is fundamental to our lives, influencing everything from our relationships to our societal structures. But is there a natural limit to how many meaningful connections we can maintain? According to Dunbar's Number, the answer is yes. This theory, developed by anthropologist Dr. Robin Dunbar, suggests that humans can sustain around 150 meaningful relationships, a figure rooted in our brain's cognitive capacity.


Understanding this concept not only reveals the constraints of social dynamics but also holds valuable insights for hospitality design, architecture, and organisational development.



“Show me the 5 people you spend most of your time with, and I’ll show you your future” is a well-known quote we have all heard many times. Your chances of success or failure, becoming fit or obese, smoking or not, being happy or depressed, happily married or divorced are all influenced by how many of your close friends do the same.

 “Dunbar’s Number,” a theory that suggests humans can only successfully keep up to 150 interpersonal relationships. Vintage illustration features a person holding an ornate frame with "150" inside. Ornate borders, geometric lines, and "Mr. Dunbar" text.
“Dunbar’s Number,” a theory that suggests humans can only successfully keep up to 150 interpersonal relationships.  | Emmanuel Lafont

It also seems to grow and contract to a precise formula, roughly a

“rule of three”: 1.5 our intimate relationship, 5 our intimate friendships (the ones we spend the most time with), followed by successive layers of 15 good friends (the friends we can turn to for sympathy), 50 friends (the people we’d invite to a group dinner), 150 meaningful contacts (the number of people we’d invite to a large party or wedding), 500 acquaintances, and 1,500 (the people we can recognise.)


Dunbar’s number  Illustration of concentric circles with a person reading. Text: 5 loved ones, 15 good friends, 50 friends, 150 contacts, 500 acquaintances, 1500 people.
Dunbar’s Number | Emmanuel Lafont

Whilst all these numbers belong to the same sequence, it’s the number 150 that is most well known as Dunbar’s Number, so named after Dr. Robin Dunbar, a British anthropologist and professor of evolutionary psychology at Oxford University. He theorised that humans could have no more than about 150 meaningful connections. People migrate in and out of these layers, but the idea is that space has to be carved out for any new entrants.


Dunbar became convinced that there was a ratio between brain sizes and group sizes through his studies of monkeys and apes. By observing their grooming habits, he discovered a definitive cohesive social circle within primates. Combining this with neuroimaging, he developed a theory that the size of the neocortex (the part of the brain linked with language, cognition, and conscious thought) relative to the body size is linked to the size of the cohesive social group and theorised that this ratio limits how much complexity a social system can handle.


Extrapolating this exact ratio from primates to humans, he arrived at the number of 148, casually rounded up to 150 as the natural upper limit of people in a group. As it turned out, the number 150 proved to be surprisingly common in organisations of all kinds.


The average group size among modern hunter-gatherer societies (where there was accurate census data) was 148.4 individuals. It was the average size of villages from the 6000 BC Neolithic villages in the Middle East (judging by the number of dwellings) to 11th-century English villages. Whilst the Spartans used a 144-man basic formation, most modern armies and fighting units still contain an average of 130 to 150 people. The Hutterites in South Dakota limit their farming

communities to 150 individuals and split them up when reaching this size.


These basic structures have lasted thousands of years under extremely testing conditions. In context, consider for a moment that almost everything we engage with daily, from the car, the airplane, and the television to the personal computer, the internet, and the smartphone, is only 100 years old. By contrast, our neocortex is roughly the same size as our Palaeolithic ancestors’ from 200,000 years ago. Although much has changed around us, our personal hardware has not, and thus these numbers are hard-coded within us no matter how advanced we may think we have become. Exceeding that number leads to all sorts of complications.



“It’s one of the magic numbers in group sizes,” contends Facebook Chief Product Officer Chris Cox, who joined in 2005 when the internet company had fewer than 100 employees. “I’ve talked to so many start up CEOs that after they pass this number, weird stuff starts to happen,”

Cox said at the Aspen Ideas Festival this summer. “The weird stuff means the company needs more structure for communications and decision-making.” Staying with Facebook, is there a difference between the physical and the digital world? Are the limits the same? Yes, according to Dunbar. It may look different at face value, but in reality, it is not.

“What Facebook does and why it’s been so successful in so many ways is it allows you to keep track of people who would otherwise effectively disappear. It’s really just providing you with another mechanism for contacting friends,”

Dunbar says.


150, as it turns out, is an invisible barrier for most social groups and organisations, beyond which growth, cohesiveness, culture, and relationships inevitably start to break down. To this end, it is an ongoing area of fascination for architects in its application to buildings and the backbone of countless businesses and social structures.


“It just looks as though it’s the same design features of the human mind that are imposing constraints on the number of individuals you can kind of work with mentally at any one time,”

Dunbar mentions.


Dunbar’s Number offers profound insights into the natural limits of human relationships and their impact on social cohesion. Whether in hospitality design, organisational structures, or community planning, understanding these boundaries helps create environments that foster meaningful connections and sustainable growth. By respecting the hard-wired social capacities of our brains, we can design spaces and systems that align with our inherent nature.


 

Information Reference Index:

How to Assemble the Ultimate Dream Team With Dunbar’s Number(s)

The Limits of Friendships

Can You Have More Than 150 Friends?

The Dunbar Number: How Biology is Linked to Organisation and Collaboration

Something Weird Happens to Companies When They Hit 150 People

Dunbar’s Number and Modern Networks

Social Structures and Cognitive Limits

150: The Magic Number of Social Connections

The Science Behind Dunbar’s Number

Dunbar’s Number: Why It Matters



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