People are accustomed to assuming of sociopaths that they are all violent criminals. But in The Sociopath Next Door, Martha Stout reveals that a shocking 4 percent of ordinary people have an often undetected mental disorder, the chief symptom of which is that the person possesses no conscience. They feel no guilt for anything at all. One of the primary characteristics of this disorder is that the individual has a charisma that makes them more charming than others, and tricky to identify.