Hmm interesting. I only ever get them when I get v* sick, even though I'mget reflux and indigestion quite a bit too yet never really had much of a problem with it. Still, it's a handy factor for me, every time I feel extremely nauseas, I burp, if it doesn't make me bellow "YUK!" I get a wave of relief knowing it's only worry or "imaginative" nausea.

I've been studying it for a long time. It turns out that it's a common symptom of Gastroenteritis (AKA "Stomach flu") which is where I first learnt that even some of the deeper intestine contents can be shoved back up into the stomach. Basically, the food might not go back up to the stomach whereas what I call "gut gases" move up, therefore causing the foul part.