Humans Can Maintain a Maximum of 150 Stable Relationships

Did you know your brain puts a literal cognitive limit on the number of stable, meaningful relationships you can maintain?

This is Dunbar's Number: 150.

Research confirms that our energy-hungry brains (consuming 20% of our energy!) evolved specifically to manage complex social ties. But that ability has a hard cap.

In the 1990s, British anthropologist and psychologist Robin Dunbar found a direct link between the size of a primate's neocortex (the part of the brain responsible for thought and complex social behavior) and the size of its social group. Extrapolating to humans, the number of stable relationships that can be maintained at any given time is consistently 150 - and hasn't changed even in the age of digital media.

For a social group to remain stable, its members must be able to coordinate their behavior, meet needs, and resolve conflicts. As the group size increases, these requirements become more demanding on cognitive resources.

Here is how your network breaks down, cognitively speaking:

• The Core 5: The innermost circle of family/friends you are emotionally closest to (your "shoulders to cry on").

• The Next 10: Good friends you see at least once a month (Total 15).

• The Next 35: A wider circle of friends or "weekend backyard barbecue group" (Total 50).

• The Outer 100: A broader social circle of people (e.g., colleagues) you know, recognize, and wouldn't feel awkward chatting with at an airport (Total 150).

This research perfectly validates an observation I've seen play out countless times:

→ Meaningful Social Support - reliable people who provide emotional support (such as active listening and reassurance) and promote feelings of being valued and connected.

→ Reduced Stress Load - dependable family/friends who give practical assistance (like helping with tasks or chores); and engage with you in relaxing activities that provide a distraction from worries.

→ Stronger Mental and Physical Health - a social network that boosts mood, fosters sense of purpose, and increases overall happiness. Strong social ties are associated with lower blood pressure, lower cholesterol, and a reduced of risk of heart disease. Social connection can also help the immune system fight off illness.

The effort we invest in those Core 15 people directly pays dividends in our long-term health.