It's like PageRank for people. Unlike websites, however, it seems that people can be too well-connected. In a study published this week, David Westerman and his colleagues showed students mocked up Twitter accounts reporting information on swine flu. They found that tweeters with an intermediate number of followers — 7,000, rather than 70 or 70,000 — were judged as most likely to know what they were talking about and to be telling the truth.
A similar study from 2008 found that strangers on Facebook were ranked as most likeable—and even physically attractive—if they had a middle-ranking number of friends. The sweet spot was around 300, rather than a few tens, or a thousand.
Too few connections, it seems, shows that someone doesn't inspire trust or affection. But too many is the mark of a hoarder, someone who spends their effort on boosting their numbers, not on genuine interaction. It's not hard to estimate from a person's friend or follower count how they spend their online social time, and how much attention you'd get if you joined that person's circle.
Westerman's Twitter study also found that tweeters were rated as most competent when there was a narrow gap between the number of people following them and the number of people they followed. This, the authors suggest, may be a cue that the person behind the account is sociable, inquisitive and a good reciprocator.
Results such as these show how people are adapting to online life — no surprise, given that our species has managed to adapt to every other physical and social environment on the planet. True, the effect of network size on likeability and credibility is pretty small — it's hard to argue that counting someone's followers is a better measure of their credibility than reading their tweets. but then, people have only just begun working out how to parse this information. And as it becomes more common for people's first contacts to be via online social networks, and as networking sites become places people go to for breaking news, this kind of information may become more important.
These findings also hint at what online society might be doing to the size of our social groups. There are various measures and predictions of this, the most famous being 150— Dunbar's number, based on plotting the size of the neocortex against social group size in humans and other primates. (Going by that, a Facebook friend is worth half a real-world friend, which sounds plausible.)
Robin Dunbar's idea (I'm writing off the top of my head here) is that primates without language have to maintain social bonds by grooming. We do so with language, which is less time- and energy- intensive, and can involve more than two people at once. So we can live in larger groups.
But even talking only allows you to connect with so many people at once. In the flesh, large conversational groups fragment naturally, because it's easier than shouting or trying to get a word in edgeways. But online, physical space is not limited, and there's not the same problem with everyone trying to speak at once. It's also much easier, and less awkward, to eavesdrop on an interesting conversation without joining in.
All this should make it possible for people to maintain larger social groups, albeit with weaker connections. On the other hand, a recent study by Dunbar and his colleagues found that people who spent lots of time on social network sites did not have larger offline networks, or closer offline relationships. So maybe what we're seeing is people developing online and offline social worlds that, to a degree, serve different purposes.
These kind of findings also suggests that as norms about online social behaviour develop the upper limit of people we connect to online could be set, not just by the physical demands of keeping in touch, but by the social demands placed on us by the judgment of our peers.
However, my pathetic Twitter numbers (54 followers, 21 following at time of writing) shows that I'm the last person you should trust on this.