Facebook has come under fire in the last few days after it was revealed the company had altered the news feeds of nearly 700,000 users in a psychological experiment. The scientists behind the experiment quickly put together an apology and explained the tests Facebook ran, but now one of the company’s top executives is speaking out about the project. COO Sheryl Sandberg called the experiment poorly timed and went on to apologize, reports The Wall Street Journal. During the one-week experiment, which took place in 2012, Facebook lowered the number of either negative or positive posts that users would see in their news feeds.