And furthermore, lots of people are really, really dumb. I got an A in honors high school chem and that was only five years ago, and I had to visit Wikipedia to check every word more obscure than "solution" in that description of saline - the average patient probably did worse or didn't take the class at all, took it longer ago if they did take it, and remembers less. Heck, there's probably a scarily high percentage of people who wouldn't even understand you if you told them it was saline.

Now there is an interesting question: can you be held morally responsible for lying if you just don't have the time/patience/ability to explain something moderately complex to someone really stupid? What if they don't even know the word "placebo" - then what do you do? Explain scientific controls and psychosomatic effects while you're trying to extract a bullet, or what have you, from your patient?

I would imagine that's not a case of stupidity, but of the brain working in a way that's (usually, more or less) efficient. Instead of analyzing the specific words you're using, the nurse, who has no reason not to trust you, analyzes the content of what you're saying, the urgency and manner with which you're presenting the evidence against this chemical that's just "blahblahblah" to the brain.

This is a way of filtering out irrelevant content and only paying attention to what is (likely) to be relevant. I had a related problem when learning to drive--my brain doesn't instantly process "right" or "left" as belonging to the specified direction, but when the instructor or person giving the test bellowed a word at me, I knew to turn and turned whichever way made more sense to me in context--which wasn't always the right decision. I don't think everyone has this thinking style, as evidenced by my instructor's irritation with me, but it's certainly not overall a bad one--in general, it's probably better to pay attention to information from the environment when operating heavy machinery, to the emotional content of a social situation rather than to etymological clues, and so on.