Psychopaths aren't devoid of human empathy, they just have the ability to switch it on and off, a new study suggests—though they do tend to default to "off". The study hooked criminals diagnosed with psycopathy up to a brain scanner, and showed them video clips of two hands touching each other: in neutral, violent, caressing, or rejecting ways. If researchers asked the subjects to identify with the person whose hand was being treated that way, the part of the brain related to pain lit up, the BBC explains. Otherwise, it lay relatively dormant.
Researchers are calling the phenomenon the "empathy switch," and say it offers new hope for psychopaths. "The predominant notion had been that they are callous individuals, unable to feel emotions," the study's senior author says. "Now that we've shown they have empathy—even if only in certain conditions—we can give therapists something to work with." (Read more psychology stories.)