Did he really understand or could he just parrot an answer? Generally I find if you can't step through with someone taking the socratic approach then you don't truly understand it. Not to say there's not room for facts, particularly at the boundaries of our knowledge, but from the description I get the impression that you were trying to teach and the professor wanted someone to recite.

There is no question of parroting, as these was not classroom exercises, but discussions between grown-ups trying to grapple with something difficult in the laboratory. After the Professor's explicit explanations, the student was able to carry on intelligently with the discussion and did not get stuck as he did with my Socratic explanations.

That still leaves the possibility that he only understood things in a rote-ish way. But if so, that was enough to get him unblocked and thinking about the other related stuff we were talking about. That's valuable in itself, and will contribute to his understanding of the original sticking point.

For some, understanding grows with reciting. There's nothing wrong with memorization iff it is followed by understanding.

And if you "step through", it's not a socratic approach any more. It's a test.

> And the student had no trouble understanding.

But did he still understand it a week later?