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 behaviours.
"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."
We Tell Everyone Where We Are
Some platforms, like FourSquare, were designed to show the world our locations. Others, like <a href="http://www.huffingtonpost.com/news/instagram">photo-sharing app Instagram</a>, make it too easy for us to inadvertently give ourselves away. In fact, we're so accustomed to snapping "artsy" pics of puppies and salads that it's possible we're unintentionally sharing our whereabouts, particularly if the photos aren't categorized as "private." So if you call out of work sick, make sure you don't accidentally post a picture of yourself relaxing at the local beach. Or, if you're feeling paranoid and want to minimize unwanted attention, go to your Instagram "Options" page and select the "Photos Are Private" button.
We Don't Respond When We're Being Watched
For many years, we were able to read Facebook messages at our leisure -- and then promptly ignore them. But the social network <a href="http://newsroom.fb.com/News/434/A-New-Look-for-Facebook-Messages">rolled out a new feature</a> that lets users see when a recipient has read a chat or message they've sent. So if you want to avoid the awkward realization you've ignored someone, type a message back, don't open the message to begin with, or use this <a href="http://crossrider.com/install/14917-chat-undetected">Chat Undected extension</a> to regain your excuse for not responding.
We Stalk In Plain Sight
<a href="http://www.huffingtonpost.com/news/okcupid">OkCupid</a> and <a href="http://www.huffingtonpost.com/news/linkedin">LinkedIn</a> are used for notably different purposes, but these social networking sites share a potentially embarrassing feature. Both platforms show who has viewed your profile. When you're checking out someone else's profile they can see you, too, which makes cyberstalking a not-so-anonymous act. In order to privately dig into another person's information, both websites offer premium memberships that'll cost you a few extra bucks a month but will let you check out as many profiles as you want on the sly. Creepy? Nah...
We Tell The World We Love Sideboob News
On a given day, we might read a few news articles online, "Like" a slew of photos on Instagram or listen to a couple of tunes via Spotify. Thanks to <a href="http://www.huffingtonpost.com/2012/01/20/facebook-frictionless-apps_n_1213970.html">Facebook's Timeline apps</a>, all these activities can be posted to your Facebook profile without the use of a manual "share" button. That's right, all your co-workers know that you've been reading stories about celebrity sideboob sightings. Every app has different preferences, so be sure to read the details of what you're allowing Facebook to publish.
We Live-Tweet Our Commutes
Sometimes we want people to know where we are. And sometimes we forget to turn off Twitter's geo-location feature, which publishes the location where we're tweeting. Too many times we've left a digital footprint mapping out our route to work, along with our favorite coffee shops and our favorite after-work watering holes. <a href="http://www.huffingtonpost.com/2011/03/07/what-not-to-post-on-twitter_n_829903.html#s245051&title=Confessionals_Office_Gossip">Be wary of oversharing</a>. A simple Google search for your name will probably call up your Twitter handle. If you want to limit who can see your profile, go to Twitter's "Settings" page and check the "Protect my Tweets" box, or turn the location feature off (seen in the image to the left).
We Turn Ourselves Into Walking Advertisements
Occasionally, companies will offer customers rewards for "Liking" their brand on Facebook. You might be a sucker for incentives, but don't forget that once you "Like" an <a href="https://www.facebook.com/FacebookPages">organization's Page</a>, you'll receive corporate updates that have the potential to litter your News Feed. Your "Likes" might also show up in your friends' News Feeds. So "Like" accordingly!
We Neglect Our 'Other' Inboxes
When was the last time you checked your <a href="https://www.facebook.com/help/188872764494245/">"Other" Messages</a> on Facebook? This hidden folder displayed in the top left corner of the Messages screen holds posts from people you're not connected with on Facebook. But who remembers to look there? Not us. The same rings true for Direct Messages on Twitter, or InMail on LinkedIn. While these modes of communication can be awesome resources, sometimes we forget they exist.
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.
After feeding Facebook preferences into an algorithm, they created models which were able to determine male sexuality with 88% accuracy, race with 95% accuracy, political leanings with 85% accuracy and religion 82% of the time.
But few users clicked "likes" which explicitly revealed these traits.
For example, fewer than 5% of gay users clicked obvious links such as "Gay Marriage" and instead inference were drawn from more popular likes such a music and TV shows.
The finding could be used to direct personalised marketing to web users but also highlights potential threats to privacy.
Kosinski said: "I am a great fan and active user of new amazing technologies, including Facebook.
"I appreciate automated book recommendations, or Facebook selecting the most relevant stories for my newsfeed.
"However, I can imagine situations in which the same data and technology is used to predict political views or sexual orientation, posing threats to freedom or even life.
"Just the possibility of this happening could deter people from using digital technologies and diminish trust between individuals and institutions."