We often take it for granted that we know the difference between a cat and a dog. Where and how do we store the visual information that categorizes “catness” in our minds, so that the next time we see a cat, we know that it is not a dog?Earl Miller has studied this process of categorization with monkeys to better understand the human brain’s processes. Miller’s research is focused on the prefrontal cortex, the part of the brain responsible for higher level intellectual or “executive activities”. A monkey’s brain is monitored to see how its “cat- recognition” neurons fire electric signals that enable this process to work. He has determined that the prefrontal cortex is extremely active when the monkey learns a task, and then goes “offline” when the task becomes automatic. Like humans learning to drive a car, at first we focus mental effort on each act of steering or braking, but eventually driving becomes somewhat routine. Mapping neural and chemical pathways for these executive brain functions may ultimately lead to therapies for dysfunctions such at attention deficit hyperactivity disorder and autism.