I think alot of people confused +25% science SPAWN rate with +25% science effectiveness(humans DO NOT HAVE THIS), see it alot in theses forums. And this thread.
Edit and all that means, and i could be wrong which i am sure someone will correct me and i will learn something new, is that a humans base % on scientist generation starts at 25% instead of 0%, still a slight chance that you will have to wait til it gets to 100% to get a scientist.