If it seems like your Facebook friends are a bit more depressed than usual, blame Facebook. The social media site recently revealed that it tweaked the news feed of about 700,000 users to see how they reacted to positive or negative posts. Facebook’s researchers were studying how emotions can be spread on social media, and basically used us as its lab rats. The study found that moods are, in fact, contagious – if you see more positive statuses, you’re more likely to post something positive, too. While Facebook has defended and praised the study, everyone else is less than thrilled. Researchers have condemned the study and said it breached ethical guidelines because of “a lack of informed consent.” Facebook argues the study was okay because we give the company permission to do research when we agree to its Terms and Service. But reports say Facebook’s Terms of Service didn’t include the word “research” until after the experiment was over – which is all the more reason for us to read those lengthy agreements before we click “OK.”