Facebook like button years of questions from the public about whether it had an intention to incorporate a "Dislike" button, Facebook officially rolled out "Reactions" to users worldwide on February 24, 2016, letting users long-press on the like button for an option to use one of five pre-defined emotions, including "Love", "Haha", "Wow", "Sad", or "Angry". Reactions were also extended to comments in May 2017. The like button is one of Facebook's social plug-ins, in which the button can be placed on third-party websites. Its use centers around a form of an advertising network, in which it gathers information about which users visit
Criticism of Facebook their behavior. For instance, in "A 61-Million-Person Experiment in Social Influence And Political Mobilization," during the 2010 elections, Facebook users were given the opportunity to "tell your friends you voted" by clicking on an "I voted" button. Users were 2% more likely to click the button if it was associated with friends who had already voted. Much more controversially, a 2014 study of "Emotional Contagion Through Social Networks" manipulated the balance of positive and negative messages seen by 689,000 Facebook users. The researchers concluded that they had found "some of the first experimental evidence to support the controversial claims that