Why Do We Touch Our Mouths So Much? (continued)

I asked this question in arecent post. If you look at people sitting in an audience, about one-third of them will be touching their mouth.

A few days ago I was on the subway. Of the persons sitting, the usual fraction were touching their mouths. Nobody standing was touching their mouth with their hands but now and then I noticed them purse or lick their lips.

Which suggested an answer to my question: We get a small amount of pleasure from touching our mouths. The pleasure declines after it is “harvested” and takes several minutes to become available again. This mechanism evolved because it kept our lips moist. At the time it evolved, people spent little time sitting. The pleasure was obtained by pursing or licking your lips, which moistened them. Predictions: 1. if you watch people whose hands are busy, they will purse or lick their lips roughly as often as people in an audience touch their mouths. 2. The more you lick or purse your lips, the less you will touch them with your hands. 3. The more you touch your lips with your hands, the less you will purse or lick them.

Pagophagia (compulsive ice eating) is similar. It iscaused by anemia(too little iron). In the Stone Age, there was no ice. An intense desire to crunch something in your mouth would have led you to crunch bones. Bone marrow is high in iron. It’s another mechanism that worked well in the Stone Age but now malfunctions (not that there’s anything wrong with touching your mouth with your hand). My self-experimentation is all about this sort of thing. It’s easy to sit, so we don’t sleep well. It’s easy to be inside in the morning, so we don’t sleep well. It’s easy to eat breakfast, so we don’t sleep well. it’s easy to avoid faces in the morning, so we get depressed. And so on.