I think it's safe to say that most people, including myself, think of ourselves as more competent across disciplines than we really are. I'm constantly having to correct that self-perception, reminding myself that I don't know very much outside my specialization. It might be as simple as picking up a book of linguistics and not even understanding what issues are at stake except very vaguely.
I'm interested in those places where disciplines are most obdurate, most settled in their own technical languages, where the insights don't automatically translate. To be really interdisciplinary you would have to actually know how to think in another discipline.