“There is nothing to which nature seems so much to have inclined us, as to society,” wrote Montaigne in “Of Friendship”, an essay celebrating and mourning his BFF, Etienne de La Boétie. According to research cited by the evolutionary psychologist Robin Dunbar, however, men are much less likely to have a “best friend forever” than women, who are more socially skilled in general. This finding might have surprised Montaigne, who supposed women lacked the “constancy of mind” even to be adequate friends to their husbands.
Dunbar belongs in the rarefied ranks, along with Avogadro and Euler, of those who have had a number named after them. His own is 150, which represents a rough cognitive limit to the number of people we can have a stable social relationship with, and so is more or less the natural human group size. In this pleasantly chatty book, a miscellany of modern research on sociableness, he rehearses this argument and his other famous idea – that language evolved so that gossip could replace time-consuming mutual grooming – as well as citing lots of other social-science experiments. Some, to be sure, will not amaze anyone who is not a literal extraterrestrial: “We gain a surprising amount of information from the nonverbal cues that we wrap around our words when we speak,” for example, though it’s not surprising at all. Others are more interesting: the fact, for example, that people who sing together in choirs subsequently enjoy an increased pain threshold, or that conversations involving more than four people are unstable and will usually split into two.
Dunbar discusses what is known about the neurochemical mechanics of such bonding effects in music and other communal activities, as well as how people actually pursue friendship in the modern world. The main theme is that sociality is computationally extremely expensive for our poor grey matter – the number of friends you have is correlated with the size of your brain areas associated with social processing – but the expenditure has remarkably concrete health effects. People with better social support networks are more likely to recover after heart attacks or strokes; more broadly, having friends can save your life. “This finding has really caught everyone completely by surprise,” Dunbar emphasises.
Our circle of around 150 “friends-in-general” contains smaller concentric circles, too. Most people have an inner “sympathy group” of around 15 people to which we devote about 60% of our total “social effort”, and a smaller ring of about five intimate friends, which Dunbar dubs the “support clique”. One intriguing aspect of his treatment is that he doesn’t distinguish too much between friends and family: “In many ways,” he remarks, “family are just a special kind of friend and so play the same role.”
Montaigne would disagree – he says, for example, that friendship sometimes requires criticism, but sons should not criticise their fathers, so they can’t be true friends. The point of Dunbar’s picture, though, is that we only have a certain number of mental “slots” for amicable relationships of any kind: “We first slot all our family members in and then, if we have any spare slots left, we set about filling them with unrelated friends,” he suggests. “It seems likely that friends in this sense are a relatively recent phenomenon, and are a consequence of the dramatic reduction in family size that has occurred over the last two centuries, especially in Europe and North America.” Indeed, people in cultures that still respect traditional extended-family ties tend to have fewer friends. If you’re spending so much time with aunts and cousins, after all, something else has to give.
It follows, too, that spending a lot of time on social media – because of the pretty hard limits to the brain’s social capacity – might preclude maintaining as many face-to-face relationships. From his analysis of high-volume tweeters, Dunbar suspects there might be a real problem here: “It implies a degree of social isolation that I had never really anticipated.”
None of which makes for especially cheerful reading when physically hanging out with your friends is actually illegal. In normal times, “the endorphins triggered by the presence of friends tune the immune system and give us enhanced resistance to [...] bugs”, as Dunbar celebrates, but right now they might just give us Covid. Meanwhile, Zoom tends to force sociality into the straitjacket of the office-meeting form, representing another victory in the creeping corporatisation of personal life. “Eating and drinking with close friends needs to be done regularly,” Dunbar wisely reminds us, which will only sharpen the reader’s hunger for an eventual return to communal feasting. Perhaps we can even imagine a time when “eat out to help out” is no longer the name of a plague-spreading subsidy initiative but simply a slogan of good psychic health.
• Friends: Understanding the Power of Our Most Important Relationships is published by Little, Brown (£20). To buy a copy go to guardianbookshop.com. Delivery charges may apply.
