How many friends can you have? For years, science has said that the limit is about 150. Has Facebook — or other social networks, for that matter — managed to change anything? Can the Internet help us maintain more friendships?

An Oxford anthropologist and evolutionary psychologist who is one of the leading experts on those questions decided to take a look. And for the latter question, Robin Dunbar found that the answer is largely no, even for social media users who friend others freely.

Dunbar, who gave his name to “Dunbar’s number” (which refers to that 150-person limit on casual friendships for any given individual) published his findings from a study of 3,000 adults in Royal Society Open Science this month.

“Given the extensive use of social media, the question as to whether Internet-based social networking sites have a positive or negative impact on social relationships has been much debated,” Dunbar wrote. “Cyberpessimists have argued that the Internet has detrimental effects on our social life. In contrast, cyberoptimists have insisted that the effects have been beneficial in many different ways.”

Dunbar outlines several levels of friendships and relationships in his work. According to his model, each person can maintain about five people in their support group of closest friends, about 15 people in a sympathy group who are close enough to confide in, about 50 close friends, about 150 casual friends and about 500 acquaintances. In all, Dunbar’s work indicates that any given human can identify about 1,500 faces, total.

The numbers aren’t exactly the same for everyone. For instance, Dunbar writes that there is some variation in size across personality, age and sex.

Dunbar’s recent results indicate that social networks stay about the same size as outlined above, even with the expanse of online “friendships” that are theoretically available on sites such as Facebook.

“The constraints that limit face-to-face networks are not fully circumvented by online environments,” Dunbar writes. “Instead, it seems that online social networks remain subject to the same cognitive demands of maintaining relationships that limit offline friendships.”

So why do “friend” groups get so large on Facebook? It might have something to do with how social networking sites label connections — most sites don’t allow users to sort friends by Dunbar layer. On Facebook, you can “friend” or “unfriend, even though users with larger networks are actually expanding their “friend” list with lots and lots of acquaintances, Dunbar concluded.

Friendship isn’t entirely blind to online connection, however: Although Facebook can’t give you more friends, it can help you maintain friendships through online contact that might otherwise deteriorate.

Friendships change, and not always for the better: Your connection to a member of that coveted circle of five best friends can “decay” over time without contact.

“Social media may well function to slow down the rate of decay,” Dunbar concluded. “However, that alone may not be sufficient to prevent friendships eventually dying naturally if they are not occasionally reinforced by face-to-face interaction.”

There’s one more big outstanding question here: What about the teens? Dunbar’s study focused on adults, in part because children and teens “are relatively poor at judging relationship quality,” and because teenagers tend to be more “exploratory” in their use of social media to find new friends — a phenomenon that is different from the general population.

But Dunbar also speculates that other aspects of teenage social media use might support his research findings, indicating that even for more exploratory teens, the task of maintaining large social networks eventually hits a limit. Particularly of interest to Dunbar? Teenagers have moved away from using open-ended sites such as Facebook as their primary social networks and instead rely on a handful of ever-changing, more private services, such as Snapchat.

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