Your brain's Twitter limit

Twitter’s approach to easy social connections lets people build big networks, often quickly. Celebrities attract millions of followers. Even non-celebrities can develop many thousands of friends; some resort to automation tools to build their following more rapidly. But what do all these connections mean? Clearly, one can’t interact with all these people on a regular basis. New research shows that there’s an upper limit to how many truly interactive social contacts we can handle.

Long before Internet-based social networks existed, British anthropologist Robin Dunbar proposed that the size of our brain’s neocortex limited the number of stable social relationships a human can handle. He estimated that it was between 100 and 230, with 150 being the most commonly used single value. This has become known as “Dunbar’s Number.”

Scientists at Indiana University decided to put Dunbar’s Number to the test by analyzing the Twitter activity of 1.7 million individuals. The team, led by Bruno Goncalves, found that Twitter users’ relationships topped out in the exact range predicted by Dunbar: 100 to 200 maximum. (Full paper: Validation of Dunbar’s number in Twitter conversations.)

While new users begin with few active friends, as identified by frequent and regular exchanges, the number of these relationships grow over time. Then, even for the most active users, their social bandwidth maxes out – they hit the proverbial wall, and simply can’t keep building active relationships.

The correlation of social network friend limits to Dunbar’s prediction for in-person relationships certainly suggests that he was on the right track in suggesting that there is a neurological constraint at work.

So, don’t be impressed by people with many thousands of Twitter friends; chances are, their REAL friend count is well below Dunbar’s limit. (I include my own Twitter numbers in that caution!)

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