I tracked down the study that Dr. Melfi read that caused her to fire Tony. Evidently, if you treat sociopath with understanding, you’ll make them better sociopaths. Here’s a link: http://www.criminology.fsu.edu/crimtheory/samenow.htm  Scroll down the page to get to the study, it’s fascinating. I found this in yet another article about the charms of The Sopranos, "The Long Con" by Emily Nussbaum in New York magazine. http://nymag.com/news/features/33517/  to read the story. Nussbaum thinks that we viewers were suckered into caring for a monster and that Melfi was right to fire him.