Forbes writes: Facebook conducted a massive psychological experiment on 689,003 users, manipulating their news feeds to assess the effects on their emotions.

The details of the experiment were published in an article entitled “Experimental Evidence Of Massive-Scale Emotional Contagion Through Social Networks” published in the journalProceedings of the National Academy of Sciences of the United States of America.

The short version is, Facebook has the ability to make you feel good or bad, just by tweaking what shows up in your news feed.

The experiment tested whether emotional contagion occurs between individuals on Facebook, a question the authors (a Facebook scientist and two academics) tested by using an automated system to reduce the amount of emotional content in Facebook news feeds. The authors found that when they manipulated user timelines to reduce positive expressions displayed by others “people produced fewer positive posts and more negative posts; when negative expressions were reduced, the opposite pattern occurred.”

Read the full article Gregory S. McNeal from Forbes here.