> There are fMRI scans that can show who is and isn't a psychopath. You show pictures to people while their brains are being scanned of situations that would evoke an emotional/empathetic response in non psychopathic people and watch for certain parts of the brain to light up. Some doctor was able to determine he was a psychopath just by looking at his own brain scan. https://www.smithsonianmag.com/science-nature/the-neuroscientist-who-discovered-he-was-a-psychopath-180947814/