You have three brains—the triune, the limbic, and the cortex—and they’re all fighting for dominance as you go about your life. The so-called lizard brain (the triune) is perhaps the one we tend to think of as instinctual and gives us our basic instincts like, for example, staying alive or not touching fire. The limbic brain controls our emotions like fear and desire, while our cortex gives us the knowledge that makes us human. Basically, the three brains talk to one another and vie for rank in certain situations… it’s sort of like Three’s Company except with brain systems. For instance: you’re reminded of something sad by your cortex and it triggers your limbic system, or you get cut off in traffic your lizard brain can trigger the cortex and the limbic. It is a pretty fascinating subject, and Robert Sapolsky waxes poetic about the three distinct “characters” that live up inside your head.