You can only have this many friends. Science says so.

By MELISSA WELLHAM

How many friends do you have?

Not Facebook friends, real friends. People whose birthdays you can remember without the aid of social media, people who you’d have sent Christmas cards to back when you actually sent Christmas cards, people who you honestly care about.

How many do you have?

Science says you can’t have more than 150.

150. That’s very precise. Pray tell science, how’d you come up with this number?

Well, this number was developed by anthropologist Robin Dunbar, who wanted to figure out a way to see how many valued friendships people can have – a “proxy for meaningful social connection”.

Bloomberg Businessweek reports:

He was curious to see not only how many people a person knew, but also how many people he or she cared about. The best way to find those connections, he decided, was to follow holiday cards.

Working with the anthropologist Russell Hill, Dunbar pieced together the average English household’s network of yuletide cheer. The researchers were able to report, for example, that about a quarter of cards went to relatives, nearly two-thirds to friends, and 8 percent to colleagues.

The primary finding of the study, however, was a single number: the total population of the households each set of cards went out to. That number was 153.5, or roughly 150.

I initially thought that 150 seemed like too large a number.

150 people I wanted to send Christmas cards to? That seemed like a lot of postage when there are also actual Christmas presents to buy and Boxing Day sales to participate in. (I had my eye on a metallic snakeskin dress at Sportsgirl. What’s more important: friendship, or metallic snakeskin? Yeah, no competition.)

I was disbelieving, that is, until I sat down and wrote my Christmas cards at the end of last year (yes, I am someone who still does that). I wrote 120. And that’s the number I wrote after I cut down the list because I was getting bored of trying to come up with creative new ways of saying nice things about people.

The Dunbar number suddenly seemed very accurate – especially if I break the 150 down into the types of friends that I have.

According to Dunbar, these 150 friends are usually distributed along similar lines. You will have an inner circle of five or so friends – people you can call at any time of the day and night, about anything.

Then another circle of about an extra ten friends – the people you definitely want at your birthday dinner. Then another 35 people – your extended circle of friends, or friends from mothers’ groups, or other clubs. And then a final 100 – acquaintances. Filler friends.

There, 150. Boom.

There is a Portuguese saying that sums this up pretty accurately: “You have five friends, and the rest is a landscape.” Although, I want to be clear, that the landscape is beautiful and fulfilling and my life wouldn’t be the same without it (them).

Apparently there is also a limit to how many close friends you can have – and it’s usually considered to be between 6 and 12.  While I’m sure that those of you with 13 best friends are mentally protesting already, you’ll just have to cut that 13th best friend from the list. Don’t blame me: blame your brain. Because how many close friends we can have, has to do with the size of our brains.

But the way that facebook and twitter have become everyday tools for communicating with friends and family actually makes me wonder whether social networking is rewiring our brains. Are we becoming more capable of maintaining larger friendship circles?

Studies are released every day that insist that the internet is changing the way our brains operate, whether for better or for worse. We are apparently less able to concentrate for long periods of time. We are better able to multitask.

Our sense of privacy and self-preservation has been diminished. Surely it’s also possible that, thanks to twitter and facebook, we are a little bit friendlier? A little bit better at maintaining relationships with people we don’t see every day, or who live in different states? Or in different countries?

However, studies have shown that – even taking into consideration the power of social media – people still tend to have meaningful interactions with about the same number of people.

A paper published in 2011 found that on Twitter the average number of other people a user regularly interacts with falls between 100 and 200. And though the limit on how many Facebook friends one can have is a generous 5,000, the average user has 190—more than 150, but within what Dunbar sees as the margin of error.

Ultimately, analysing the size of your friendship circles feels like a fairly fruitless exercise. Surely we should be concentrating on the quality – instead of the quantity – of our friends?

Because even if you only have three friends, and never send a Christmas card to anyone else – that’s okay. If those three people are there to support you no matter what, and let you literally cry on their shoulders and don’t care that you are getting snot all over their favourite t-shirt, and can laugh with you hysterically for fifteen minutes at in-jokes that nobody else will understand – then you don’t need more than that.

Landscapes can be beautiful – but I would rather a portrait, detailed and expressive and human, any day.

How many close, close friends do you have? Do you think the Dunbar number sounds accurate?