Fish on a Stick

This Wondermark comic from mid-September struck me as a little lesson in linguistics, although as is often the case, I am not enough of an expert in linguistics to really figure out how to talk about it. I'm only good enough to see that there is some linguistics to be talked about here.

The lesson is that language involves not just what is said but a whole bunch of assumptions that we have that help us interpret what is said. I thought this might have something to do with the Gricean maxims, but I can't figure out how the two speakers' assumptions violate those maxims of quality, quantity, relevance, or manner.

The second man assumes that if something is carrying something and shouting out a description of it, that it must be for sale. The man with the fish, though, interprets the question not as "how much do you want for it?" but as "how much of the fish is on the stick?"

Any linguists out there want to help me with this one? Perhaps I should send it to Mark Liberman of Language Log.