In "Mass Psychology and Ego Analysis"Sigmund Freud retrieves the theories of a sociologist of his time named Le Bon. According to Le Bon, the individual gains immense power by associating with a group and feels security in being part of it. However, Freud adds that this sense of belonging leads to a loss of individual consciousness. Thus, the sensations that permeate the group tend to have a great influence and to override individual consciousness. In recent years in Brazil, massified behaviors have been clearly observed, currently amplified by social media. The analysis that Freud conducted on this type of behavior remains fully valid and useful in today's world. It is this analysis that is available to the reader now in "Mass Psychology and Ego Analysis."