One major pastime for grad students is complaining about how bad our undergrads are (they, I’m sure, complain about us—I know I did when I was their age). They aren’t perfect, but sometimes their missteps can actually be enlightening.
In the most recent lab I graded, they generated this plot:
And then we asked them to consider why the two lines were parallel, even though the growth rate of the two states of bacteria (which can interconvert) are so different. One of the responses was: “because the population sizes are increasing at the same rate”. To which I whacked my head on my desk, and wrote in “yes, but why are they increasing at the same rate?”.
I’ve been thinking about it more over the last couple days, and I realized the problem is not with the student, but with the question. “Why” tends to be too broad, with many possible answers. Unless the person you’re asking is interested in the exact same things you are, and even possibly in the same mood, they might then answer the “why” question with a totally different (though equally correct) answer.