The presence of empathy (in Rhon) and anti-empathy/sadism (in Aristo) is explained by two extraneous structures in the brain, KEB and Kyle Afferent Body (KAB). The first sends out signals of emotions, while the second interprets them. The Aristos were genetically engineered for resistance to pain, and the structure that is supposed to interpret telepathic signals is defective. They do not interpret emotions as such, instead they receive only emotional signals of pain, which their brains re-routes to the sexual pleasure centers. The perfect prey for Aristos are the empaths, since the empaths sends out stronger pain emotions, which translates into greatest pleasure.