Writing
How often should you contact friends to stay close?
It depends which layer of your life someone sits in. The five people closest to you need contact roughly once a week to stay there, the next fifteen need something closer to once a month, and the fifty after that can run on a few check-ins a year. Dunbar’s layers are a set of four circle sizes, roughly 5, 15, 50 and 150 people, identified by the Oxford evolutionary psychologist Robin Dunbar as the natural groupings a person’s social effort sorts itself into. Go quiet on someone for around six months, and Dunbar’s research suggests the friendship drifts down a layer without either person deciding that on purpose.
Where do the 5, 15, 50 and 150 numbers actually come from?
Robin Dunbar is an evolutionary psychologist at the University of Oxford who, from the 1990s onward, studied the relationship between primate brain size and typical social group size, then applied the same method to humans. His best-known figure, Dunbar’s number, puts the upper limit on stable human relationships at around 150. That number isn’t a guess. Inside it sit smaller, nested layers: roughly 5 people in the innermost circle, 15 in the next, and 50 in the one after that, each layer demanding less individual attention than the one inside it.
How often does each layer actually need contact?
The inner five, the people Dunbar’s research treats as the core support circle, tend to need contact close to weekly to stay there. The next fifteen can hold their place on something closer to monthly contact. The fifty beyond that, described in Dunbar’s work as the wider friendship group, can often run on a handful of check-ins across a year rather than a fixed monthly rhythm. The numbers aren’t a strict schedule so much as a rough natural rate below which a relationship tends to start slipping outward.
| Layer | Typical size | Roughly how often |
|---|---|---|
| Inner circle | ~5 people | About once a week |
| Close friends | ~15 people | About once a month |
| Wider friend group | ~50 people | A few times a year |
| Wider network | ~150 people | Occasional contact |
What actually happens if you go quiet for six months?
Six months without contact is the rough point at which Dunbar’s research finds a relationship tends to shift down a layer: from someone in the fifteen to someone in the fifty, or from the inner five to the fifteen. Nobody sends a notice. There’s no single missed message that causes it, just an accumulated gap that eventually re-sorts where someone sits, and by the time it’s noticed, the drift usually already happened months earlier.
Does keeping a friendship take as much effort as starting one?
Less, according to a 2018 study by Jeffrey Hall, a communication professor at the University of Kansas, who found it takes roughly 50 hours together to move from acquaintance to casual friend, and around 200 hours to become close friends. Maintaining a friendship that’s already crossed that threshold costs a fraction of that ongoing, which is part of why a relationship that took years to build can still drift with surprisingly little neglect: the investment already made doesn’t disappear, it just needs topping up rather than repeating.
So should everyone contact their friends on the same schedule?
No, and this is where a fixed weekly reminder stops being useful. Two people can both sit in someone’s inner five and need completely different rhythms to feel maintained, because “normal” was set by how that specific friendship has always run, not by a rule. This is the layer where a tool like Coppice is built to help: tracking drift against a person’s own established rhythm rather than applying one schedule to everyone, since Dunbar’s layers describe typical group sizes, not a personal contact calendar for any one friendship.
Common questions
Is Dunbar’s number actual science, or just a popular idea? It’s actual research: Robin Dunbar published the original correlation between primate neocortex size and group size in 1992, and the 150 figure has since been tested, and debated, across decades of further study. The precise number gets argued over, but the general pattern, that stable relationships cluster into nested layers of decreasing size, holds up well.
Does a text count the same as a phone call or seeing someone in person? Not quite. Dunbar’s own comments on digital contact suggest a voice, on a call or in person, carries emotional cues that a text strips out, so a short call tends to do more for a relationship than a longer text exchange, even though both count as contact.
What if you can’t manage weekly contact with your inner five? Life gets in the way, and one missed week doesn’t reset anything. The drift Dunbar describes happens over months, not days, so an inner-five friendship can absorb an occasional gap without moving layers, as long as the gap doesn’t become the new normal.
Sources
- Dunbar, R. I. M. (1992). Neocortex size as a constraint on group size in primates. Journal of Human Evolution, 22(6), 469-493. The origin of the layers and the 150 figure.
- Roberts, S. G. B., and Dunbar, R. I. M. (2015). Managing relationship decay. Human Nature, 26, 426-450. The six-month threshold at which a close friend drops a layer.
- Hall, J. A. (2019). How many hours does it take to make a friend? Journal of Social and Personal Relationships, 36(4), 1278-1296. Roughly 50 hours to a casual friend, 90 to a friend, 200 to a close friend.
Coppice is an iPhone app that notices when someone you care about is drifting out of touch and nudges you at the right moment. Get it on the App Store.