Facebook users' online behaviour reveals intimate details about their personality which could allow strangers to predict their sexuality, political views and religion, researchers say.
Experts say that by studying 'likes' – the system used to show approval on the social networking site – it is possible to accurately predict what a person is like in real life.
Whether it is drug users being more inclined to show approval for Big Momma's movies or people with high IQ showing a taste for curly fries, the patterns are not always immediately obvious to the untrained eye.
Michal Kosinski, operation director at the University of Cambridge's Psychometrics Centre, said: "We believe that our results, while based on Facebook Likes, apply to a wider range of online behaviour.
"Similar predictions could be made from all manner of digital data, with this kind of secondary 'inference' made with remarkable accuracy – statistically predicting sensitive information people might not want revealed.
"Given the variety of digital traces people leave behind, it's becoming increasingly difficult for individuals to control."
The study, based on the Facebook profiles of 58,000 people in the US, found that online behaviour can be used to make surprising accurate predictions about users' race, age, IQ, sexuality, personality, substance use and political views.