Washington (AFP) - A controversial Facebook experiment on mood manipulation "messed with people's minds," privacy activists said in a formal complaint to US regulators Thursday, seeking an urgent investigation.
In its complaint to the US Federal Trade Commission, the Electronic Privacy Information Center said the study -- which has been widely criticized online -- deceived consumers and violated an agreement on privacy settings.
"The company purposefully messed with people's minds," the complaint said.
It said that Facebook's manipulation of the news feeds of Facebook users to elicit positive and negative emotional responses also "failed to follow standard ethical protocols for human subject research."
The complaint asks the US regulatory agency to investigate, to order a halt to any similar practices and to require Facebook to make public its algorithm used for the news feed.
An FTC spokesman declined to comment on the complaint.
The privacy group, which joined other groups in complaints in 2009 and 2010 that led to Facebook's 20-year agreement with the FTC on privacy, said that the huge social network did not get users' permission to conduct the study and failed to notify participants that their data would be disclosed to researchers.
The complaint came a day after British authorities announced an investigation over the Facebook experiment.
Facebook's chief operating officer Sheryl Sandberg apologized this week for communicating "terribly" about the research and maintained that "we take privacy at Facebook really seriously."
Facebook clandestinely altered the emotional content of feeds of nearly 700,000 users, giving some sadder news and others happier news in the 2012 study aimed at better understanding "emotional contagion."
The research, published last month, prompted online anger and questions about the ethics of the study, and put the world's most popular networking site on the defensive.
A 2012 settlement with the FTC prohibits Facebook from misrepresenting the privacy or security of its data.