WASHINGTON: Scientists have developed a computer algorithm that predicts whether a photo will go viral on Facebook by watching how fast it is shared.

 Stanford researchers said the clues to predicting which of the many millions of photos on Facebook will spring from obscurity and go viral lie in ‘cascades’. The term ‘cascades’ is used to describe photos or videos being shared multiple times.

 “It wasn’t clear whether information cascades could be predicted because they happen so rarely,” said Jure Leskovec, assistant professor of computer science.

 According to data provided by Facebook scientists in a recent collaboration with university scientists, only 1 in 20 photos posted on the social network gets shared even once. And just 1 in 4,000 gets more than 500 shares – a lot but hardly an epidemic.

 In a paper to be presented at the International World Wide Web Conference in Seoul, Korea, the researchers will describe how they accurately predicted, 8 out of 10 times, when a photo cascade would double in shares; that is, if a photo got 10 shares, would it get 20? If it got 500, would it reach 1,000, and so on?

 The team including Leskovec, Stanford doctoral student Justin Cheng, Facebook researchers Lada Adamic and P Alex Dow, and Cornell University computer scientist Jon Kleinberg began by analyzing 150,000 Facebook photos, each of which had been shared at least five times.

 The data were stripped of names and identifiers to protect privacy.

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