While the best way to deal with a sociopath is to avoid him or her entirely, sometimes circumstance doesn't allow for that. What happens when the time comes to defend yourself against your own child, a ruthless ex-spouse, a boss, or another person in power? Using the many emails and letters she has received over the years, Dr. Martha Stout uncovers the psychology behind the sociopath’s methods and provides concrete guidelines to help navigate these dangerous interactions.

We know of psychopaths from chilling headlines and stories in the news and movies - from Ted Bundy and John Wayne Gacy to Hannibal Lecter and Dexter Morgan. As Dr. Kent Kiehl shows, psychopaths can be identified by a checklist of symptoms that includes pathological lying; lack of empathy, guilt, and remorse; grandiose sense of self-worth; manipulation; and failure to accept one’s actions. But why do psychopaths behave the way they do? Is it the result of their environment - how they were raised - or is there a genetic component to their lack of conscience?

Patric Gagne realized she made others uncomfortable before she started kindergarten. Something about her caused people to react in a way she didn’t understand. She suspected it was because she didn’t feel things the way other kids did. Emotions like fear, guilt, and empathy eluded her. For the most part, she felt nothing. And she didn’t like the way that “nothing” felt.

Psychopathy is a personality disorder that has long captured the public imagination. Newspaper column inches have been devoted to murderers with psychopathic features, and we also encounter psychopaths in films and books. Individuals with psychopathy are characterized in particular by lack of empathy and guilt, manipulation of other people and, in the case of criminal psychopathy, premeditated violent behavior. They are dangerous and can incur immeasurable emotional, psychological, physical, and financial costs to their victims and their families.

We are accustomed to think of sociopaths as violent criminals, but in The Sociopath Next Door, Harvard psychologist Martha Stout reveals that a shocking 4 percent of ordinary people, one in 25, has an often undetected mental disorder, the chief symptom of which is that that person possesses no conscience. He or she has no ability whatsoever to feel shame, guilt, or remorse. One in 25 everyday Americans, therefore, is secretly a sociopath.