There is a very esteemed Canadian psychologist named Robert Hare, creator of the hare psychopathy checklist- revised. Apparently, he views psychopathy and something like the spectrum of colours. Murderers among psychopaths is as uncommon as murderers among non psychopaths. It's simply a range of lacking in empathy, from a minor lack of empathy, to an extreme lack of empathy. I think he postulated that 5% of all men have some degree of psychopathy. I'm sure that as women continue to emerge as equals in the workforce, we will see new tests to discover their level of psychopathy. To me, this makes far more sense than the idea that people choose to be heartless.