This may help predict social movements, consumer reactions or possible outbreaks of epidemics, researchers said.
Scientists, including those from the Universidad Autonoma of Madrid, made use of one of the properties of the social networks that can also be observed in Twitter; known as "the friendship paradox": your friends have, on average, more friends than you.
In the case of Twitter, after analysing a sample of data from 40 million users and 15 billion followers in 2009, the researchers were able to show that each user had an average of 25 followers, who in turn had an average of 422 followers, that is, almost twenty times as many.
Researchers randomly selected a group of users and took some of their followers as the sensor group.
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They found that those "sensor-friends" play a more important role than what was previously believed, because they receive information long before the previously chosen users.
"We were really surprised. We thought the method would give us a few hours early warning, but instead it gave us several days, and sometimes even weeks or months," said co-senior author, James Fowler, from the University of California-San Diego (US).
In general, this new method turns out to be very simple and effective for monitoring social networks, researchers said.
Data from just 50,000 Twitter users is enough to achieve these levels of prediction and to know what will "go viral" across the entire Internet.
The system can be used in real time, about different topics, in different languages and geographical areas, thus allowing for different contexts to be covered.
The study was published in the journal PLoS ONE.