One issue for designers of social network apps and mobile networks is the effective number of people any particular user interacts with, can interact with, and at what degree of intensity (time or emotional commitment). And it might be fair to say that face-to-face human relationships are one thing, while online social networks are another.
LinkedIn might be a social network, but mostly of people one never sees, do not really know or spend time with in any way other than occasional online messages. One analogy is that most of us on LinkedIn could not consistently match faces and names of our own connections.
Simply put, there are clear and sharp limits to emotional closeness and the number of meaningful relationships any person can have, in a face-to-face, real-world context.
The absolute limit of people any single person can even put a name and face together with numbers about 1500, according to Robin Dunbar, who developed a theory on the size of human groups now called Dunbar’s number.
Few consider that an effective social or communication network, one simply recognizes a person.
The Dunbar number suggests there are clear limits to the size of any single person’s face-to-face social network. Casual friends—the people you’d invite to a large party--might number only about 150.
Dunbar discovered that the number grows and decreases according to a precise formula, roughly a “rule of three,” where each group of more intimate friends is about a third the size of the larger group.
The number of people you might call close friends—perhaps the people you’d invite to a group dinner--number a maximum of 50. You see them often, but not so much that you consider them to be true intimates.
There’s a smaller circle of fifteen, who are the friends that you can turn to for sympathy when you need it, the ones you can confide in about most things.
The most intimate Dunbar number, five, is your close support group. These are your best friends (and often family members).
Looking at mobile network communications, some researchers have found that whether any user has a large or small network of contacts, the amount of time spent communicating was about the same.
Dunbar and a research team found, after analyzing some six billion calls made by 35 million people in an unnamed European country throughout 2007, that the rule holds for mobile communications.
The team assumes that the frequency of calls between two individuals is a measure of the strength of their relationship. To screen out business calls and casual calls, the researchers included only individuals who make reciprocated calls and focus on individuals who call at least 100 other people.
The team found some 27,000 people who call on average 130 other people.
“Compared to those with smaller networks, those with large networks did not devote proportionally more time to communication and had on average weaker ties (as measured by time spent communicating),” say researchers Giovanna Miritelloab, Esteban Morobcd, Rubén Laraa, Rocío Martínez-Lópeza, John Belchambera, Sam G.B.Roberts and Robin Dunbar.
Mobile users tend to distribute their time very unevenly across their network, with a large proportion of calls going to a small number of individuals, they note. “These results suggest that there are time constraints which limit tie strength in large personal networks.”
A study of Facebook and Twitter networks likewise found that contact frequency matched “real world” communications closely. The absolute sizes of these layers and the mean frequencies of contact with alters within each layer match very closely the observed values from offline networks, say R.I.M.Dunbar, Valerio Arnaboldia, Marco Conti and Andrea Passarella.
“Our analyses indicate that online communities have very similar structural characteristics to offline face-to-face networks,” they say.
A study by Pew Research Center found that the median number of Facebook friends is 200. How that compares to “real world” human networks is debatable. One study of LinkedIn first-level contacts found that 27 percent of LinkedIn users had between 500 and 999 first degree connections.
As with Facebook, “friends” and LinkedIn first level connections are not the equivalent of friends one knows on a face-to-face basis. In many cases, far from it. If you use LinkedIn, and think about it, nearly all the connections are business or commerce related, and almost never involve on-going relationships with people you eat with, for example.
And even some who doubt the general premise Dunbar limit do note that any bucket of people (group with tags) on a very-large contact list tend to number less than 150.
Dunbar's Number suggests no human can maintain more than 150 stable social relationships. Operationally, you would not feel uncomfortable joining that person for a drink at a bar. Most of us do not reach the "Dunbar limit."
The Dunbar number is actually a series of maximum limits. Some people might be able to know 500 acquaintances or 1500 people for whom you actually know a name.
At the upper limit, 100 to 200 is who you’d ever be able to personally invite to a large party. Perhaps 50 is the limit of those who can be close friends.
About 15 is the number of people you rely on for sympathy and confide in about most things. Five is your close support group (typically best friends and family).
Social networks online arguably are different from other human networks. Most people might have social sets online that resemble their real world interactions. But a few power users on social media also exist. The issue is that such social networks are not the same as human face-to-face networks.
