Dunbar's Number
The 150 Limit
The human neocortex correlates directly with group size. Based on brain volume, humans can maintain stable social relationships with approximately 150 people.
This is "Dunbar's Number."
The Mechanism: Recursive Mentalizing
Why 150? Because relationships require computational power.
To have a friend, you must run a simulation of their mind in yours ("Theory of Mind").
- 1st Order: "I know..."
Most humans max out at 5th Order Intentionality. This computation happens in the DMN (specifically the mPFC and TPJ). The hardware literally cannot track more than ~150 complex dynamic models.
The Fracture
In the modern world, we have thousands of "Followers" but fewer intimate friends than ever before. We exceed our cognitive bandwidth daily.
We treat strangers like enemies because our brain codes anyone outside the 150 as a potential threat. We are tribal software running on a global network.
The Inheritance of Perspective
You are not designed to care about a billion people. When you scroll the news and feel the weight of the world, you are hacking your own empathy circuits. It is okay to narrow your focus. Tend to your fire. Tend to your 150.