I should clarify a little - don't take that to mean it's okay to be pretentious, and yes, sometimes you do have to talk down to somebody else's level. (In fact, depending on your level of native intelligence, you may have to do that pretty much all day, every day!) But the take-away is to start "normal", (high), and only fall back if you have to. I've known more than a few people who worked very menial, boring jobs suggesting an IQ in the mid double digits but who were in fact highly intelligent and would not appreciate being condescended to. Their choice of work and mode of life is simply due to having a different set of priorities.