Whether we recognize the psychopath as the serial murderer in a film or the unexpressive character in a book, we have a harder time acknowledging them in our real world. Psychopathic individuals can be hard to recognize in a world crawling with mental illnesses because, unlike the physical symptoms we see in severe mental illnesses, such as hallucinations, agitation, or hostility, psychopaths do not completely manifest signs of any physical sort. So then, what are the distinctive personality characteristics that set psychopaths apart, and what causes them?