They are, it turns out, adept at mimicking normal emotive behaviours, but are incapable of experiencing emotions in the same way normal people are. They use what they know to manipulate the situation, and are more than willing to use one's empathy against one.
This is because they are genetically predisposed to psychopathic behaviours. Their amygdala (the place in the brain responsible for processing emotion and emotive responses) is underdeveloped - actually smaller than in a normal person - and, in extreme cases, what is there is not functioning correctly.
In short, they feel zero empathy and actually derive pleasure in seeing other people upset. These are the crazies who tear others down and pretend to be sad about it, when everyone else knows they do it for fun.
You know the advice the article gave for those facing a psychopath at work? Do not engage. They're better at the game than you. Run. Run far, far, far away.
I know a few people who match this description. In any case I can use this article. This article, which I can't find now, damn it, is filed in memory box 'Useful Information That Could Inform a Character One Day.'
How I love accidental research!
Barbarous Latin, such as was formerly used by lawyers in their pleadings, Now applied to 'medical Latin.'
- John Hotten's Slang Dictionary, 1887
Also kitchen-, bog-, or apothecaries'-Latin.
- John Farmer's Slang and Its Analogues, 1905