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Hey! and then…Ouch!

Why does "Ouch!" always follow the "Hey"? Find out on this Moment of Science.

One thing we don’t want anyone to do is poke themselves with a sharp object after reading this Moment of Science. But the next time you accidentally get poked you might notice something interesting.

Say you reach into a pile of clothes where a needle is sticking up. If you are able to reflect for a moment as you are sucking your fingertip, you may realize that you have had two separate sensations.

The first of these is what we might think of as the “hey!” sensation. It conveys the information that something startling has happened to your finger, and that thing is unpleasant. A moment after that comes a deeper-down feeling of pain. This latter sensation might be called the “ouch!” It’s not startling so much as just plain bad.

What’s going on here?

In fact, there are several different kinds of fibers that send pain information to your brain. These are called “nociceptors,” and they respond not only to pins but to heat, cold, chemical changes, and other dangers. These receptors send their information through two different kinds of fibers: the large, fast “A” fibers, and the smaller, slower “C” fibers.

Because they are naturally coated with a conductive substance, “A” fibers transmit messages at about 330 feet per second, whereas “C” fibers can only handle about six-and-one-half feet per second.

The delay some people can distinguish between “Hey!” and “Ouch!” is thought to be due to this time lag. It also makes sense that the faster “A” fibers would be the ones whose job it is to get you to pull your finger away right now.

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