Dunbar’s number: why depth beats breadth

Here’s a confession I’m not proud of. I’m the guy who lights up a room and then forgets to call you back.

Put me in a party and I’m approachable, funny, quick. I’ll meet you, click with you, swap numbers, mean every word of “we should catch up.” And then I’ll vanish. Not out of malice — out of some quiet, lifelong wiring. I grew up mostly with my grandmother in Agartala, my parents at a distance, and I became an introvert who is genuinely comfortable alone. I make new connections easily. I’m just terrible at watering them afterwards.

For years I told myself the lie that this was fine — that a big network was the relationship. More contacts, more LinkedIn connections, more people who’d recognise my face. It felt like progress. It felt like building something.

Then I read about a British anthropologist named Robin Dunbar, and the whole illusion fell apart.

The number your brain actually allows

Dunbar’s argument is simple and brutal: there’s a ceiling on how many stable relationships your brain can maintain, and that ceiling is roughly 150 people. He arrived at it by correlating the size of the neocortex in primates with the size of their social groups, then extrapolating to humans. Not 150 because it’s a nice round number — 150 because that’s about all the social bookkeeping your hardware can run at once.

And it isn’t a flat 150. It’s a set of nested rings, each roughly three times the size of the one inside it:

• ~5 — your loved ones. The 2 a.m. people.
• ~15 — close friends. The ones you’d grieve.
• ~50 — friends. The dinner-party list.
• ~150 — meaningful contacts. People with a real relationship, not just a face.
• ~500 — acquaintances.
• ~1,500 — people you could simply recognise.

Look at that for a second. The outer rings are huge and the inner ring — the one that actually holds your life up — is five. Five.

You don’t have a relationship problem. You have an allocation problem. You’re spending your finite social budget on the outer rings and starving the inner one.

Why we collect instead of deepen

Because collecting is effortless and deepening is effort.

That gap is the spine of everything I write about — and of the book — the move from effort to effortless, and how the easy option quietly wins. Adding a contact costs one tap. It gives you a little hit of “I’m connected, I’m building, I’m growing my network.” Deepening a friendship costs a phone call you don’t feel like making, a flight to a wedding, the patience to sit with someone through a bad year. The reward arrives slowly, if at all.

So the brain does what brains do: it picks the option with the better short-term UX. We rack up 1,500 faces and call it a network, while the five people who’d actually drop everything for us drift one un-returned message at a time. What’s effortless to do is just as effortless to neglect. And nothing is more effortless to neglect than a friendship that will, technically, survive being ignored for one more month.

I know this because I lived it. After my matriculation in 2001, when I left Agartala for Chennai, I made a conscious decision to let go of most of my school friends. Incoming mobile calls were expensive; my girlfriend — now my wife of more than twenty years — and I communicated through letters carried by a postman. Two decades on, I look back and realise most of the people who were once in my inner circle simply aren’t anymore. Some of that was unavoidable, geography and time. But a lot of it was me, choosing the effortless drift.

What changed when I stopped counting

The shift was small and unglamorous. I stopped trying to grow the network and got deliberate about filling the top three rings — the 5, the 15, the 50.

Deliberate is the key word. I started treating my inner circle like the most important allocation decision I make, because it is. (If you want something to actually do with this, there are templates and frameworks over at the resources.) That meant two things, and the second one is harder than it sounds.

First, protect the inner ring. I stay away from people who sap my energy, who blame everyone else for their problems, who trade in toxic gossip. Not because I’m above them — because a spot in my five is a finite, precious resource and I refuse to spend it on someone who drains it. In a world that tells you to be available to everyone, choosing who not to give your depth to is an act of self-respect.

Second, show up for the ones who’ve earned the spot, especially when it’s inconvenient. My wife is everything I’m not here — she maintains genuine, warm relationships with people from every walk of life, and I’ve learned more about depth watching her than from any book. Family and close ones need our support, and we don’t get to opt out because we’re busy or tired. Raising kids can be draining; answering a seven-year-old’s hundredth “why” demands a patience I don’t always have. But that’s the work. That’s the watering. You can’t collect your way into a relationship that holds.

The hard part nobody admits

Here’s the honest bit. Choosing depth means choosing loss.

Every spot you give to the inner five is a spot you’re not giving to the crowd. Every evening you spend truly present with one person is an evening of fifty shallow hellos you didn’t collect. In the Instagram age, that feels like falling behind. Some people find contentment in a few close relationships; others need a wide social network — there’s no single right answer. But the quality of the connection and the support it actually gives you will always matter more than the count.

And depth has a cost the breadth-collectors never pay: vulnerability. You can have 1,500 acquaintances and never once be truly known. To get into someone’s five, you have to let them see the unfiltered version of you — the small-town kid, the founder who took his wife’s salary to pay employees, the introvert who’s still learning how to call people back. That’s the price of admission to the inner ring, and it’s non-refundable.

I’m not writing this as someone who’s arrived. I’m writing it as someone still learning, still travelling, still occasionally the guy who lights up the room and forgets to call — you can read more of that story here. But I count differently now. I don’t ask how many people I know. I ask: who are my five — and when did I last actually show up for them?

Your brain gave you room for about a hundred and fifty. It only gave you the heart for five. Stop spending the first to avoid the work of the second.