When it comes to intelligence, we all have bad days. Heck, we even have many bad moments, such as when we forget our car keys, forget a friend's name, or bomb an important test that we've taken a day after staying up all night worrying about it. Truth is, none of us-- including the world's smartest human-- is perfectly consistent in our cognitive functioning. Sometimes we are at our very best and feel like our brain is on fire, and at other times, we don't even recognize ourselves.
