Melissa Dahl interviews R. Douglas Fields, a senior investigator at the National Institutes of Health, about the reasons why we sometimes snap:

Fields argues that there are nine major triggers that invoke the rage response, which he has assembled into the acronym LIFEMORTS: life and limb, as in your physical safety; and insult, meaning a verbal threat. The next six are self-explanatory: family, environment, mate, order in society, resources, tribe — you already know each of these are things you’d fight for if you felt they were in danger. The last is stopped, the idea that any animal (humans included) will ready itself to fight if it feels restrained or trapped. So for each of these nine triggers, the rage kicks in to prepare you for a potential fight, because you feel like something essential has been threatened.

These triggers evolved in our brains for a reason, and at times they give rise to defensive action that is as necessary for modern humans as it was for our early ancestors. But they can misfire, too, sometimes to violent, irreversible effect. Fields spoke with Science of Us about what happens inside the brain when we flip our proverbial lids, and how we can begin to control this impulse.