Facebook has considered profiling its users’ personalities and using the information to target adverts.
A patent filed by the social network describes how personality characteristics,including emotional stability, could be determined from people’s messages and status updates.
The firm is currently embroiled in a privacy scandal over the use of its data by a political consultancy.
Facebook says it has never used the personality test in its products.
The patent, first filed in 2012, is in the names of Michael Nowak and Dean Eckles.