There is a quote from the Stoic philosopher Seneca which frames this debate: “When a person spends all of her time in foreign travel, she ends by having many acquaintances, but no friends. And the same must hold true of people who seek intimate acquaintance with no single author, but visit them all in a hasty and hurried manner.”
It’s clear that Seneca believes two things here. First, Seneca believes that having lots of friends is anti-correlated with having close friends. This assumption makes sense if you think that social resources are finite. For example, if you have 10 hours to spend time with friends this week, you can either allocate those 10 hours among 10 different friends or spend it all with one single friend. Assuming that friendship is a function of the amount of time spent with someone, you’re going to cultivate a closer relationship with the one person than you would with any of the 10. Seneca’s second belief is that it is more valuable to have friends that are close rather than numerous.
Seneca has his opinion. But which is really better: more friends or closer friends?
In the corner opposite Seneca, supporting “more friends” is a theory from sociologist Mark Grannovetter. In his landmark paper on The Strength of Weak Ties, Grannovetter makes the claim that the economic value of one’s social network is not in the number of close friends you have, but in the number of arms-length acquaintances you have. It’s the weak-ties that matter, not the strong-ties. Grannovetter’s argument centers around the idea that people who you are really close to—your strong ties—share much of the same social and professional sphere that you do. They are unlikely to introduce you to new ideas or new job opportunities or any sort of information that you wouldn’t already be likely to come across without their help. Weak-ties, on the other hand, are not generally part of the same world. They have different jobs, specializations, college majors, friend groups of their own, and they are a part of environments from which you can potentially learn. Strong-ties make the world smaller, weak-ties make it bigger.
A bigger world may mean a world with more opportunities, but it goes without saying that economic gain is not the only standard by which to judge a potential relationship. Backing up Seneca, coming down squarely on the side of “closer friends,” is a theory by anthropologist Robin Dunbar, commonly known by the shorthand of “Dunbar’s number.”
Dunbar’s theory, argued in his 1991 paper on Neocortex size as a constraint on group size in primates, is that there are fundamental limits to the number of people that a human (or a chimp, for that matter) can know well. These limits are cognitive. Our social minds can only handle so much social information before getting overloaded. Dunbar’s number is most often quoted at 150, specifying, in Dunbar’s words, “the number of people you would not feel embarrassed about joining uninvited for a drink if you happened to bump into them in a bar.” This is supposed to be the optimal group size if you want everyone to know everyone else pretty well. And it can be extrapolated to suggest that this is also pretty close to the limit of one’s social groups—that is, only about 150 of your Facebook friends are people you really care about.