Brain Rule #1: The human brain evolved, too. We don't have one brain in our head—we have three. We started with a "lizard brain" or our brain stem. This part of our brain is responsible for the body's housekeeping chores: breathing, heart rate, sleeping, waking. On top of that sits our mammalian brain, which is similar to the brain of a cat. This part of the brain is responsible for the four F's: Fighting, Feedling, Fleeing, and ...reproductive behavior. On top of that sits a thin layer of Jell-O known as the cortex—the third, and powerful, "human" brain. Each region of the cortex is highly specialized with sections for speech, vision, and memory.