Revelations about a secret mood manipulation experiment that Facebook conducted on nearly 700,000 social users created a lot of bad feelings this week.

The June 17 Proceedings of the National Academy of Sciences study, led by Facebook data scientist Adam Kramer, described altering users' exposure to positive or negative comments from friends for a week in 2012.

The results suggested that positive and negative emotions are contagious, in a small way, across social media. But negative feelings were the ones spreading widely with news of the study, as ethicists like Art Caplan of New York University's Langone Medical Center raised questions about its honesty.

The University of Wisconsin, Madison's Dietram Scheufele knows a thing about the