How the brains of psychopaths and heroes show that humans are wired to be good

At fourteen, Amber could boast of killing her guinea pig, threatening to burn down her home, and seducing men in exchange for gifts. She used the tools she had available to get what she wanted, like all children. But unlike other children, she didn't care about the damage she inflicted. A few miles away, Lenny Skutnik cared so much about others that he jumped into an ice-cold river to save a drowning woman. What is responsible for the extremes of...