"Psychopaths do not lack empathy, rather they can switch it on at will..."

"... according to new research."

Psychopathy is a personality disorder characterised by superficial charm, pathological lying and a diminished capacity for remorse. Now scientists have found that only when asked to empathise did the criminals' empathy reaction, also known as the mirror system, fire up the same way as it did for the controls. Without instruction, they show reduced activity in the regions of the brain associated with pain.

I'll remember this next time I'm contemplating whether it's worth the effort to beg for mercy. I've always assumed that asking for empathy would only heighten whatever thrill the monster was obtaining from the attack.