If they're neither psychic nor have any psychic training, the risk of detection is negligible. And frankly, any psychic worth their salt should be able to peg me as one as well, because the presence of mind shielding tends to be easily detectable if you know what you're looking for.

I'll stick to passive listening rather than scanning, at least at first. Even if another psychic catches me at it, it's generally not considered rude as long as you're not actively prying, and especially not in an unknown situation.