A major Federal Trade Commission complaint has been filed against Facebook for conducting a secret study on nearly 700,000 Facebook users, without their consent or knowledge, for the purposes of internal research. The filing by the Electronic Privacy Information Center claims that Facebook “purposefully messed with people’s minds” by testing changes in emotional states by purposefully altering the news feeds of users. Beyond the questionable ethics of social-media experimentation, EPIC said the study also violated terms of a 20-year consent decree that requires the social-networking company must protect its users’ privacy. The complaint also outlines sanctions and that Facebook to be forced to disclose the feed determining algorithms it uses.

Researchers from Facebook, the University of California, San Francisco and Cornell University conducted the study from Jan. 11 to Jan. 18, 2012, on 689,003 English-speaking Facebook users. The research sought to show whether emotions can be influenced with no face-to-face contact. By manipulating Facebook’s news feed algorithm, the researchers sought to create “emotional contagion.” People with more positively influenced feeds made more positive comments and those with more negative posts were more negative in posting.

While the study was for Facebook’s internal purposes, the complaint follows outrage from Facebook users and online privacy-rights advocates after the results were published by the Proceedings of the National Academy of Sciences. Once the news emerged, researchers and eventually Facebook COO Sheryl Sandberg said that the research simply was not explained well by the company. PNAS editor-in-chief Inder M. Verma published an “editorial expression of concern” saying it was consistent with Facebook’s data use policy. When users sign up, they are giving “informed consent” that their data might be used in research. Because the research was conducted internally by Facebook, it did not fall under the auspices of Cornell’s Human Research Protection Program, the statement says.

Facebook issued a brief statement that the company will not comment on the complaint. The statement further notes that as a private company Facebook is under no obligation to follow what is known as the “common rule” among researchers, to obtain informed consent from study participants and allow them to opt out if they don’t want to be part of the research.