Man, I spent an hour going back and looking for that study.
It’s done by some Stanford University guys....Mathew Gentzkow is one. https://news.stanford.edu/2017/01/18/stanford-study-examines-fake-news-2016-presidential-election/
The entire study: https://web.stanford.edu/~gentzkow/research/fakenews.pdf
The study basically says that you can feed a ton of fake news into the social media scene, and the bulk of it really doesn’t matter...people don’t retain that level of knowledge.
After reading the piece, I started to think about college classes, high school, and how the bulk of information you are given....usually is forgotten within a month or two....same type of memory issue. Personally, I’d like to see more research like this done.