How come we can't smell our own breath? --- Christen, Seattle, Wash.
Marshall Brain Answers:
Imagine that you walk into a tire factory for the first time. The initial thing that hits you is the incredible noise. Then when you take your first breath you cannot believe the smell - curing rubber, adhesives and solvents create a shocking mix of odors. The floor is vibrating because of a nearby piece of machinery and you can feel it through the soles of your shoes. It is warmer than you would like. You ask yourself, "how could anybody possibly work here???"
But an hour later you would find the situation completely different. Your body has adjusted. You don't even notice the smell, or the noise, or the vibration or the heat anymore. Because they are constant, your body has tuned all of them out.
The process is called habituation. And it is a good thing it's a built in feature of just about any animal's nervous system. Otherwise you would feel your clothing touching you every time you move, or hear the sound of every tiny noise (the air conditioner, the computer's fans, the ticking clock) in the room. It would all drive you absolutely nuts if you didn't habituate.
The smell of your own breath is the same way. The smell is constant, so your brain tunes it out and ignores it. But there is a way to smell it if you would like - check this page.