The author] reveals [in this book] that a shocking 4 percent of ordinary people--one in twenty-five--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.... They can do literally anything at all and feel absolutely no guilt.... Fundamentally, sociopaths are different because they cannot love. Sociopaths learn early on to...