Facebook's Sheryl Sandberg offered an apology Wednesday for what she characterized as poor communication about a controversial experiment that tested users' emotional reactions, although she did not concede any problems with the study itself.

"This was part of ongoing research (that) companies do to test different products, and that was what it was. It was poorly communicated," said Sandberg, according to The Wall Street Journal, which said the social network's chief operating officer spoke with business executives and entrepreneurs in New Delhi, India.

"And for that communication we apologize," she added. "We never meant to upset you, "

Sandberg is the first senior Facebook executive to address a controversy that erupted after researchers reported they tested the emotional reactions of nearly 700,000 Facebook users for one week -- without their knowledge -- by reducing the number of positive or negative updates from friends that appeared in their news feeds.

Critics say the study manipulated users' emotions without getting "informed consent" or meeting other ethical standards that apply to academic or government research involving human subjects.

A Facebook researcher announced the study earlier this month in a scientific journal article that said their findings could have implications for public health. But since then, Facebook has argued the study was no different from other tests that online companies conduct to gauge users' reactions to different messages or advertising.


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The difference could be significant, legal experts say, because research to develop proprietary products or services isn't subject to the strict ethics oversight that usually applies to published research aimed at advancing scientific knowledge.

Sandberg's statements did not mollify some of the study's outspoken critics.

"If so many people are uncomfortable, it is better to start listening, rather than issue weak, 'We regret you are upset'-type statements," Zeynep Tufekci, a sociologist and assistant professor at the University of North Carolina School of Information, said in an email interview with this newspaper.

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