You may have heard that Facebook manipulated the content of user's New Feeds during January of 2012 so that some users saw more positive posts than others, which other Facebook users saw more negative posts.  How did this affect these users?  Did those who say negative posts become more negative and vice versa?  The answer is that the research indicates that some of them - though a very, very few of them - did subsequently write posts that were similar to the ones that saw on their News Feed.  How big of an effect is this?  Is it unethical?  Does agreeing to Facebook's Terms of Use constitute "informed consent".  I examine these questions in this episode of The Psych Files.