The hidden rules behind our best friendships

Hidden intrinsic rules underlie the shapes of our friendships and social connections, influenced by everything from our gender to our sleep schedules, says Oxford University Emeritus Professor Robin Dunbar.

The anthropologist and evolutionary psychologist is know for coming up with 'Dunbar's number' of 150, which he says is the highest number of stable relationships we can maintain with at any one time.

He also says our friendships tend to be governed by a network of patterns we aren't necessarily aware of.
 
Dunbar nods to one of the great modern philosophical quandaries: how many, among your Facebook friends can really be described as a friend.

"This is the dilemma of Facebook and similar social media," he says. "It's the way they want you to sign up as many people as possible ... but in reality our social world is very small. Typically it's somewhere round about 150 people.

"It's not to say you can't sign up more people on Facebook, or indeed that you don't know more people in everyday life, but the 150 limit really is the number of people who have meaningful relationships with."

And there are more patterns that have arisen from study that give more clues about our surprisingly unique social fingerprints.

"We really were surprised by this, looking at people's phone calling pattern, and the time the time they devote to each of the friends and family in their list. Not too surprisingly some people you call more often ,and some people you call perhaps once a year at Christmas to catch up and say 'how are you?'

"But what transpired that we hadn't expected was that the pattern in which you allocate your time and effort to the different people in your social network varies between people in quite marked ways, so it's very much like a fingerprint, and the pattern is quite unique to you.

"Roughly speaking we spend something around three hours a day engaged in social interaction with people - that doesn't count the time you spend at work, in work-related interactions.  Most of it's obviously done in the evenings and the weekends.

"Of that three hours a day, around about 40 percent is devoted to just five people, your five closest friends and family. And then another 20 percent is devoted to the next 10 closest people to you - these are averages.

"So those 15 people consume about 60 percent of your total social effort whether you measure this by emotional capital, or as simply time spent with them.

"On the other hand the other 135 people that make up the rest of your social network have to make do with something that comes close to about 7 seconds each [a day]. So they've got to wait quite a few months before they get a decent look-in."

Another rule Dunbar utilises is a "30 minute rule", developed by Canadian sociologists, which he says has proven very robust.

"Your willingness to make the effort to go round and see somebody depends critically on how far away from you they actually live. If they live 30 minutes away from you, you'll go and see them at the drop of a hat.  

"If they live beyond that 30 minute limit then you'll be more selective in whether or not you'll just drop in on them. You''ll only do that for big occasions, like a big birthday or something.

"It doesn't seem to make any difference if it's 30 minutes on foot, 30 minutes by bicycle or 30 minutes by car."

Despite carrying out many of our friendships by phone or digitally he says the 30 minute rule still applies.

"It seems that the medium of communication doesn't seem to matter too much; if you look at people's face to face contacts, the frequency with which they telephone people in their social circles, their texting frequencies, the frequency with which they post to them on Facebook or other social media - it's all pretty much the same.

"We treat Facebook much as we would treat a face to face contact. There is a view that we phone people that we can't go and see very often - and up to a point that's true, but that's the once in a year phone call at Christmas, say, to see how great grannies doing.

"But in fact we telephone people who live near us more often because we see them more often, because we want to make social arrangements to catch up with what they've been doing today.

"These modes of communication are kind of interchangeable, despite the opportunities that digital media offer us."

Dunbar says without cultivation, friendships tend to decline back to acquaintanceships.

"It probably takes about three years of not seeing them at all. It probably isn't your best friends ever, or at least the level of decay on those friendships is very very slow indeed.  

"I think there's a very small cluster of very good friends that you've had over the years that are kind of resistant to this. These seem much more like family relationships, which are much more resistant to decay than friendships are - and we've always assumed that's largely because they're embedded in a very extended interconnected network, say Aunty Jane can tell you what's happened to cousin Pat, whereas friendships tend not to be quite so embedded in networks of that kind."

A recent study he undertook looked at how moving away from home affected young people's networks.

"The way in which the males and females maintained friendships and how they kept them going through being separated was really strikingly different.

"What allowed the girls to maintain old friendships was by investing much more time than they had formally into keeping contact with them. Primarily language and conversation-based; phoning or texting, and Facebook posts to them.

"Whereas conversational contacts had absolutely zero effect on the boys' friendships. They boys' relationships died or did not die, irrespective of how often they talked to each other.

"Parents with teenage sons will know this phenomenon very well, it's the grunting teenager - boys don't talk," he chuckles. "But what was very striking was - what made the difference between a friendship decaying and a friendship remaining stable over distance was making the effort to go and do stuff together.

"Whatever they used to do, whether playing five-a-side football together, or climbing mountains, or just going and having a beer together. That was much more important. So... boys peering morosely into their beer may look an unhappy lot, but actually they're bonding."

Women typically have a wider circle of friends than men, he says.

"I'm not sure there are such big differences in the outer layers. But it's particularly so for the inner layers, the closest friends - the shoulders-to-cry-on friends who will drop everything to give you support, or the layer outside that - the sympathy group, the people you really feel emotionally engaged with, which is typically about 15 people.

"That's because [women's] social cognitive skills are much better than men's, and that allows them to keep more social balls in the air at the same time without dropping them."

From a study examining phone company records and later studies, he says there's a difference to be seen in the friendships of night owls and morning people, and a similar division between introverts and extroverts.

"Clearly the world is divided into people who are primarily daytime people, and the rest who are primarily nighttime people, and the two don't mix. It's inevitable really, because if you're a daytime lark and your friend is an owl, and you want to go to bed and they want to go clubbing this is not going to work.

"Introverts on the whole tend to prefer introverts as friends, and extroverts tend to prefer extroverts. But extroverts and larks who feel more confident in social environments don't mind being rejected once or twice, and are prepared to have weaker relationships.

"The amount of social time you have available is the same for introverts and extroverts, it's just a question of how many people you partition it among. The extroverts and the larks, in parallel, seem to prefer to have more friends but to spread their time more thinly between them."