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Photo: The Canadian Press. All rights reserved.

FILE - In this Dec. 13, 2011 file photo, a sign with Facebook's "Like" logo is posted at Facebook headquarters near the office for the company's User Operations Safety Team in Menlo Park, Calif.  (AP Photo/Paul Sakuma, File)

Clicking those friendly blue "like" buttons strewn across the Web may be doing more than marking you as a fan of Coca-Cola or Lady Gaga.

It could out you as gay.

It might reveal how you vote.

It might even suggest that you're an unmarried introvert with a high IQ and a weakness for nicotine.

That's the conclusion of a study published Monday in Proceedings of the National Academy of Sciences. Researchers reported analyzing the likes of more than 58,000 American Facebook users to make guesses about their personalities and behaviour, and even whether they drank, smoked, or did drugs.

Cambridge University researcher David Stillwell, one of the study's authors, said the results may come as a surprise.

"Your likes may be saying more about you than you realize," he said.

Stillwell and his colleagues scooped up a bucketful of that data in the way that many advertisers do - through apps. Millions of Facebook users have surveyed their own personal traits using applications including a program called myPersonality. Stillwell, as owner of the app, has received revenue from it, but declined to say how much.

His study zeroed in on the 58,466 U.S. test takers who had also volunteered access to their likes.

When researchers crunched the "like" data and compared their results to answers given in the personality test, patterns emerged in nearly every direction. Since the study involved people who volunteered access to their data, it's unclear if the trends would apply to all Facebook users.

The study found that Facebook likes were linked to sexual orientation, gender, age, ethnicity, IQ, religion, politics and cigarette, drug, or alcohol use. The likes also mapped to relationship status, number of Facebook friends, as well as half a dozen different personality traits.

Men who liked TV song-and-dance sensation "Glee" were more likely to be gay. Men who liked professional wrestling were more likely to be straight. Drinking game aficionados were generally more outgoing than, say, fans of fantasy novelist Terry Pratchett. People who preferred pop diva Jennifer Lopez usually gathered more Facebook friends than those who favoured the heavy metal sound of Iron Maiden.