Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School by John Medina

If someone asks, "What is the single most important organ in our body?" Many of us will answer that it is our brain, and you’d be correct. But thank about it, how did you take in their question? How did you come up with a response? What allowed you to move your mouth, lungs and vocal chords to answer? That’s right, it was your brain. As the most important organ in our body, it governs our emotions, thinking, and behavior. In our daily lives, we need the brain to call the shots for nearly any of our responses. Imagine how different our lives would be if the brain sustaining our daily life is damaged. Although we cannot directly experiment with our brains to observe the effects of neurological injury, an accident that befell a railroad worker named Phineas Gage brought to light some mysteries of the brain.

At one point, Gage was using explosives to construct a railroad when the dynamite ignited early. The shock wave blew a 3-foot-long, 7-inch-wide steel rod through Gage's skull. The rod entered the left side of his face, penetrated his prefrontal cortex, and flew 30 yards behind him. Gage miraculously survived, and his body functions fully recovered. However, his personality changed forever. Gage used to be a kind man with an iron will, but after the accident he frequently engaged in rude and insulting behavior and tried to control other people. Furthermore, he was rarely submissive and often seemed very impatient with others' disagreements. Why was this so? It was because of the damage to his prefrontal cortex, making him unable to control his impulses.