This week's experiment is a chance for you to do some scientific research on a problem that has never been solved. We all yawn, and you have probably noticed that if someone else yawns, you do too. Why? There are several hypotheses, but none has enough solid evidence to become an accepted theory.

For this investigation, you will need:

- several people in different situations

Experimentation has shown that when one person yawns, others around him will often yawn too. You don't even have to actually yawn. Just saying the word "yawn" can sometimes cause people to yawn. So can the sound of a yawn, even if you can't see the person that is yawning. In fact, reading this experiment may cause you to do it. Why? No one knows.

One idea was that it had to do with a lack of oxygen in the blood, but that was easy to disprove. Putting volunteers in a room that had lots of extra oxygen in the air, and comparing that with volunteers in a room with very little oxygen did not show any difference between the two groups.

Another idea was that we yawn because of boredom, but athletes often yawn just before they compete. That does not sound like a boring time to me.

To try some research of your own, try yawning in different situations. For example, I know from my experience as a science educator that while I am teaching, someone in the audience yawning will not make me yawn too, but if I yawn on stage, it seems to make quite a few people in the audience yawn.

Try yawning while shopping, in a doctor's waiting room, at a fast food restaurant, etc. After yawning, watch for a few minutes, to see how many people yawn. Pay attention to who yawns. For example, is it easier for parents to make children yawn than for children to make their parents yawn?

Recent studies have shown that yawning is contagious in chimpanzees, but it does not seem to work that way for all animals. Try yawning in front of your cat or dog, to see if it is contagious for them. From my experience, a cat can make me yawn, but my yawns don't seem to have any impact on cats or dogs.

Do your yawns have a different effect on the same person in different situations? What about at different times of the day? Or in different emotional states?

There are all sorts of things that you can investigate with yawns. Who knows, you might be the one that figures out the real "why" in yawning.