The problem is that this question gets asked once or twice a month, and it comes up so often that a lot of us are tired of seeing it, especially since if you don't answer it, people are all like, "Ah, no responses, eh? I must be RIGHT!"
These threads end up in arguments a lot, and they tend to get everybody all riled up.
Mucca, if you want scientific evidence, look in the archives for a post by SDSubbio or something to that extent for the text "PR abstracts" or something like that.
Plus, you'll find a lot of threads that talk about other answers to this question. One that came up is, "Just because there's no scientific evidence, doesn't mean it doesn't work." We actually don't know why airplanes fly. We use lift and drag to describe fundamental reactions, but we still don't know WHY planes fly. No scientific proof. But they do, and we have a whole industry out of what's basically a paradox.
PRing is based on NLP research and cognitive science. It's been said that they've ripped off other systems and added their own touches to it. In either case, the placebo effect would probably not affect a comprehension test, since you would have actually comprehended the text, not "felt" like you did.
The real question is, "Does the system work?" and the answer is, "Yes, it does."
We might not know why, or how, but ask people who are comprehending material at 3 times the regular speed, and they'll tell you more than a bunch of graphs and lines will.
-Ramon http://razor.ramon.com
