People experience fear for lots of different reasons, including scary movies, scary holidays, and scary weather. But I got my heart rate up recently by doing something that barely fazes some folks: I went to the dentist.

While I reclined in the chair, feeling anything but relaxed, my heart danced the rhumba and my hands curled into tight balls.

"Yy gaaahch," I said. "Huh unn eye uwhwayy uh?"

(Translation, for those who do not speak Dental Patient: "My gosh. What am I afraid of?")

The dentist has a friendly smile full of inspirational teeth. Even though her name is Dr. Carrie--just like that star of the Stephen King book and movie--she isn't the least bit scary.

But what she was going to do to me was. My rational brain knew she was shooting me full of anesthesia to prevent pain, yet the little animal inside of me was scared of pain anyway. The little animal wanted out of the chair.

And this, my friends, is what we call a touch of dentophobia.

I say it's only a touch of dentophobia because a real phobia is a serious thing, much more serious than my meager case of the willies.

A phobia is an intense, persistent fear of a specific object or situation. Often, the fear is so bad that the person who has it can't lead a normal life. In one instance I learned about as a college student, a woman with a bad case of agoraphobia developed a cyst that grew to weigh 303 pounds. Her fear of going out in public was so bad she let this cyst get to be the size of a linebacker. Amazingly, doctors were able to remove it successfully.

But enough of that. Why, if I knew Dr. Carrie was getting me good and numb, was I still afraid?

The answer, I have learned, is that I couldn't help it. Dr. Peter Lang, a graduate research professor at the University of Florida, studies fear. He's also director of the prestigious National Institute of Mental Health Center for Study of Emotion and Attention.

Lang told me that the whole idea of "waking up in the morning...doing things because we want to" is not how human beings really work, no matter how much we like to think it is. Yes, we do have a rational mind that helps us make decisions based on compelling evidence. Our subconscious minds, however, do a lot of the driving.

Lang and other researchers believe that humans--like other animals--have two basic modes. One is "appetitive." Like the word "appetite," appetitive describes things we want. Our other mode is defensive. These are our two motives: Either we want something, or we are protecting ourselves against a threat. This is how the human species has managed to perpetuate itself and survive.

In my case, I wanted to get that yucky hole in my tooth filled. But I was afraid that Dr. Carrie might hurt me with her drill. In this particular battle, healthy teeth won. But it doesn't mean my inner animal didn't throw a fit inside my rib cage.

So, what was happening to me in that dentist's chair, anyway?