Facebook studies the personal characteristics of its users and uses the information available about them to post targeted ads.
A patent provided by the social network shows how character traits, including emotional stability, can be determined by people’s messages and status updates.
Facebook is still involved in a scandal over the privacy of its users after their data was used by a consulting firm.
Facebook says it has never used personal testing in its products.
Facebook offers a tool that allows the user to control the privacy of his data
The patent, first introduced in 2012, was registered as Michael Nowak and Dean Eckles.
Nowak has worked for Facebook for 10 years, while Eckles is now studying at the Massachusetts Institute of Technology.
The patent has occurred twice, most recently in 2016.
The BBC has seen e-mails from Eckles and other Facebook staff to Cambridge University psychologists discussing data analysis to infer users’ personal characteristics, and talk about using such research to improve the product for users and advertisers.
Cambridge Analytica, a political consultancy, has claimed that it used a similar technique, known as marketing psychology, in its work, although it denied the use of Facebook’s personal test data in the 2016 US presidential election.
The patent in Facebook says potential sources of data may include “status updates, notes, messages, posts, comments, or any other communications from which linguistic data can be extracted.”
Eckles told in an interview that his search included asking Facebook users to complete questionnaires asking personal questions, explaining that FSBOC was behind these questionnaires.
He acknowledged that “marketing psychology advertisements targeting users raise some ethical concerns,” but said he doubted they would be applied at any time.