The nice man from Tokyo Gas came today to turn on the stove and hot water at the place I'll be staying for the next two weeks or so. I used one of my patented tricks on him, something that works every time to convince Japanese people that I am Wonder Gaijin, capable of linguistic feats that absolutely transcend the humanly possible. This is also, importantly, a method that can be applied in a wide variety of situations, and which speaks to some deep function of human intersubjectivity.
It works like this. The gas guy (or any given Japanese person) is talking a blue streak at me, which usually happens pretty quickly after I greet them with a reasonably confident "Konichi wa" and explain to them that "I don't speak much Japanese" in decent Japanese. I do not understand much, if any, of the specifics of what he's explaining to me. But about halfway through the chat I pick out a word - you can pick out pretty much any word, you don't understand any of them, remember - and stopped him, puzzled. I repeated the word a couple of times, then went to grab my dictionary. I figured out what the word was, made a slight "o" of recognition while nodding gently, then looked at him, cueing him to continue. I then proceeded to not understand the bulk of what followed.
As he was leaving, the mechanic told me that in the entire time he'd been working the job, I was the best Japanese-speaking foreigner he'd met. At least, I think that's what he said.
The lesson here is pretty simple. If you make a big, ostentatious deal out of not understanding one very specific element of a conversation, presentation, or what have you, then your interlocutor is likely to assume that you understood everything else that they said. It's a misdirection, a slight-of-tongue, a gaslighting - the one point of misunderstanding effectively distracts from even the possibility that you didn't understand anything else being said, either. This could be an effective tool/weapon in, say, a graduate classroom ("What exactly do you mean by gradation?") or a boardroom ("I'm not sure I'm following your point about ISO ratings."). I hope all of you use this insight responsibly, but I'm more concerned with the deeper structure we're encountering here . . . in precisely what way does a protestation of ignorance make your erstwhile silence seem like comprehension?