Patric Gagne realized she made others uncomfortable before she even 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.

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 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.

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.

Most people are both repelled and intrigued by the images of cold-blooded, conscienceless murderers that increasingly populate our movies, television programs, and newspaper headlines. With their flagrant criminal violation of society's rules, serial killers like Ted Bundy and John Wayne Gacy are among the most dramatic examples of the psychopath. Individuals with this personality disorder are fully aware of the consequences of their actions and know the difference between right and wrong....