The Prof that I worked for when was in academia, who was really quite bright - his PhD was in non-linear control systems, had a wonderfully endearing habit of being quite open when he didn't understand something - he did this in way that made it obvious he was asking because he was generally genuinely interested in what people were telling him and wanted to make a decent effort to understand it.

I seem to remember that he was particularly delighted when, although he had no programming experience, someone explained how Unix fork() works!