How Facebook Knows You Better Than Your Friends Do

In the movie Her, Joaquin Phoenixs character falls in love with his computers operating system, which through the magic of machine learning and Hollywood comes to know and understand him better than anyone else. Its a futuristic critique of human reliance on technology. But according to one new study, its a future that may not be all that far away.

This week, researchers from the University of Cambridge and Stanford University released a study indicating that Facebook may be better at judging peoples personalities than their closest friends, their spouses, and in some cases, even themselves. The study compared peoples Facebook Likes to their own answers in a personality questionnaire, as well as the answers provided by their friends and family, and found that Facebook outperformed any human, no matter their relation to the subjects.

Thats a substantial finding, the researchers say, particularly given the fact that human beings are evolutionarily designed to have good personality judgement. Its what keeps us out of danger and influences our relationships. But the realization that, perhaps, computers are better equipped to make these judgements than humans are could help cut through the natural bias that pervades human interactions. Never mind what this says about how much of power Facebook wields.

Were walking personality prediction machines, says Michal Kosinski, a computer science professor at Stanford, but computers beat us at our own game.

The researchers began with a 100-item personality questionnaire that went viral after David Stillwell, a psychometrics professor at Cambridge, posted it on Facebook back in 2007. Respondents answered questions that were meant to root out five key personality traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism. Based on that survey, the researchers scored each respondent in all five traits.

Then, the researchers created an algorithm and fed it with every respondents personality scores, as well as their Likes, to which subjects voluntarily gave researchers access. The researchers only included Likes that respondents shared with at least 20 other respondents. That enabled the model to connect certain Likes to certain personality traits. If, for instance, several people who liked Snooki on Facebook also scored high in the extroverted category, the system would learn that Snooki lovers are more outgoing. The more Likes the system saw, the better its judgment became.

In the end, the researchers found that with information on just ten Facebook Likes, the algorithm was more accurate than the average persons colleague. With 150 Likes, it could outsmart peoples families, and with 300 Likes, it could best a persons spouse.

Whats more, at times, the Facebook model could beat the subjects own answers. As part of the survey, the researchers also asked respondents to answer concrete questions such as how many drinks they have a week or what type of career path theyve chosen. Then, they tried to see if they could predict how many drinks someone was likely to have in a week based on their answers to the personality test.

Once again, they found that Facebook Likes were a better indicator of peoples substance use than even their own questionnaires were. When people take the questionnaire, they present themselves in a slightly more positive way than they really are, Kosinski says. This tendency to self-enhance makes computers slightly more objective.

While the researchers admit the results were surprising, they say theres good reason for it. For starters, computers dont forget. While our judgment of people may change based on our most recent or most dramatic interactions with them, computers give a persons entire history equal weight. Computers also dont have experiences or opinions of their own. Theyre not limited by their own cultural references, and they dont find certain personality traits, likes, or interests good or bad. Computers dont understand that certain personalities are more socially desirable, Kosinski says. Computers dont like any of us.

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How Facebook Knows You Better Than Your Friends Do