It's no secret that Facebook is a goldmine for advertisers seeking to target specific demographics — but it may surprise you to discover just how much of your personality is revealed by simple activities there. Researchers from the University of Cambridge and Microsoft Research have been quietly (and innocuously) collecting data on Facebook user likes and personality traits using applications like "MyPersonality" on Facebook, and now they're showing how the data can be used. Simply by tracking what things you've liked on Facebook, the researchers say they're able to determine things like your sex, ethnicity, political leanings, and religion with accuracies over 80 percent.

The findings were published today in the Proceedings of the National Academy of Sciences, based on data that you can dig into yourself on a public wiki. Demographers have always been able to come up with shockingly accurate data based on what seems like limited information, but the new study makes it crystal clear that Facebook likes are a richer source of personal information than they seem. Just because you have set your personal information to private doesn't mean that somebody can't find out a lot about you based on what you've left public.

Clicking the "like" button on "The Joy Of Painting With Bob Ross," is one of several indicators that it's likely that your parents didn't separate before you turned 21, while (appropriately, this week) liking "Austin, Texas" could be combined with other likes to indicate drug use. Although Facebook likes are an especially good way of gathering data, just ignoring that button probably isn't enough to put a veil between your profile and demographers. "Similar predictions could be made from all manner of digital data," says Michal Kosinski, "statistically predicting sensitive information people might not want revealed."