Ah! That's interesting! I've never actually had that be difficult at all. Every time I ask "I'm just trying to get X. Is that something you can speak to?", I get a pretty concise answer, even if the response itself is meandering and non-committal (that's a "no", if you're unclear).

Would you have an example of a discussion where you weren't able to determine if both people were working towards the same goal?