[edw519]

"Is there a single question..."

No. And there shouldn't be.

Instead of spending time and energy trying to determine the perfect quesiton, why don't you just spend that same time and energy actually talking to people.

Talk about anything. Listen as much as you talk. "Engage" them. After 5 minutes of sincere (this is key!) interaction and a half dozen subjects, you'll probably have a pretty good idea of where their heart is.

A low tech solution that has been working very well forever. All it takes is a little practice.

OTOH, if you don't do this and probe with a single question, you'll look phony and won't learn anything.

[frossie]

Agree with edw519 entirely. I should add that we always arrange for a sightseeing tour and meals with interview candidates in order to facilitate talking on a variety of subjects. These activities are chaperoned not by the people who will interview them, but people who would work with them if they got hired. We also give them interview tips, and brief them on the background and style of the people who will interview them. The best interview is one without surprises.

(We're not google, we only shortlist 4 people at a time, and hire rarely, so we can afford to take the time).

[Tangurena]

Exactly, What the OP is looking for is some sort of "litmus test" to apply to candidates.

http://en.wikipedia.org/wiki/Litmus_test_(politics)

There exists no single question that is usable to filter good from bad candidates. Interviews are littered with nonsense like "what is your greatest weakness" because some idiot thought that to be some useful litmus test.