h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Old threads never die, nor even completely fade away it seems, KB

Same reason as when you stare fixedly at an object of a given color for a minute or so and then transfer your gaze to a neutral field, you see a rather blurred after-image in the reverse of the color of the object ypou were staring at in the first case, reason rooted in the opponent process mechanics of sensory-perception.

http://en.wikipedia.org/wiki/Opponent_process

http://gettingstronger.org/2010/05/opponent-process-theory/

http://www.alleydog.com/101notes/s&p.html

http://www.wisegeek.com/what-is-opponent-process-theory.htm

I sometimes retch when brushing my teeth in the morning too. I thought it was to do with the toothpaste taste when full with breakfast.

After eating raw onion, I always want to eat chocolate.

You beat me to it, KB - looking up old tea threads.

Wretching is a natural gag reflex, part of the autonomic system
which instinctively rejects intrusion into open bodily orifices.

Hint:
The molars at the back should be approached from the side so that
brush strokes run across the mouth rather than threaten to go down
the throat.


~jwf~

But I can happily brush my teeth at other times of day. It's more brushing behind front teeth that makes me gag.

Back of the front teeth, eh.

Sounds more like an olfactory gag response then.


~jwf~

Its possible to train to lose the gag reflex somewhat though... apparently

Clearing the nose first also helps to turn off the gag and retch response.