I first noticed this effect in college, when the prof would be talking about something that didn't make sense to me. If I remained silent, he'd never explain (of course) and I'd remain ignorant. However, whenever I asked him, everyone would start furiously writing down his explanation in their notes. So I got into the habit of saying "I don't understand". Inevitably, there would be quite a number of other people who…
Did you usually just say "I don't understand"... or was it more like "I get how a works with b when c occurs. But you lost me when you were talking about how it happens over z, I don't get the distinction, could you go into that?" It's not about plain ignorance, but conscious incompetence. That can be a great deal of work to attain in a given domain, getting to that "I know what I don't know" place so you can actuall…
I'm a teacher and I like students who ask me to re-explain or re-present a step in an argument. In fact, I use techniques designed to find out how much my students know and 'how they know it'. I teach fairly basic Maths, and different students learn the basics in different ways.
I'd like a student who could articulate which step in a complex argument is the issue even more! I usually ask follow up questions to find out where the issue is without putting the questioner on the spot.