When shown a tempting image, such as a juicy cheeseburger, or asked to solve a hard problem, activity in parts of the brain associated with emotional response (the amygdala and orbitofrontal cortex) supersede activity in the part of the brain tasked with thoughtful, rational thinking (the prefrontal cortex). Other experiments show that after someone is forced to exert self-control, activity in the prefrontal cortex diminishes altogether.
