<p>I hope one would not think I was suggesting that profs at other schools are not engaged with their students, I have many friends who teach and include undergrads in research that would take issue with that. I was simply pointing out a single experience of an interaction a Chicago prof had with a student who was no longer in his class. To amykins point, what bothered S was the lack of interest by his classmates in the question. He said at Chicago there would have been a race to the board to join him in figuring it out. Conceivably, it is the atmosphere of joint engagement that is perhaps defining of the Chicago experience (though I am sure one will find instances of that as well at other schools).</p>