Our insula neurons don’t distinguish between disgusting smells and disgusting behaviors, explaining metaphors about moral disgust leaving a bad taste in your mouth, making you queasy, making you want to puke. You sense something disgusting, yech . . . and unconsciously, it occurs to you that it’s disgusting and wrong when those people do X. And once activated this way, the insula then activates the amygdala, a brain region central to fear and aggression.[4]
