A recent study found that Facebook tends to lead to agenda-setting rather than changing the opinions of users.
Agenda-setting is the idea that the media determines what stories and events are important and newsworthy. The study suggested that based on what stories certain people were shown on Facebook, their opinions on what the current important topics are shifted.
However, agenda-setting is not the same as changing opinions. This means that Facebook isn’t changing people’s political views with what it is showing.
You can read more about the study here.