Being fascinated with psychopathic killers. Look at the nation’s highest-rated television series and best-selling books. Chances are many of them feature psychopathic killers. Scientists who have studied this behavior offer several explanations. One possible theory is that when we watch a psycho on TV, we enter into his or her mindset for a while. This allows us to not think about others’ needs, since psychopaths only think about their own needs. Another explanation argues that because psycho killers are predators, watching them takes us back a step in our evolutionary history to a time when humans had to become predators to avoid becoming prey. Finally, some scientists say that our craving for stories featuring psychopathic killers give us a rush of adrenalin, which after being released, are followed by other hormones that give us pleasure, such as dopamine and serotonin.