In acting, there is something in the world of improv referred to as 'blocking'. The basic idea is that whenever someone introduces and idea you have to think "yes, and" as opposed to just "no". The house is on fire! Yes and my cat is on the top floor, we have to save it! If you don't know what to do with it you shouldn't just completely ignore it. Along the same lines it doesn't help just to stall and say yes its on fire and send it back to the other person with nothing added. Also, check out this article at www.thewayofimprovisation.com, where the case is made that saying "Yes, and" can also be blocking if it de-rails the established reality. I think these things have interesting parallels in music.
In jazz jam sessions (like our weekly Tuesday jam) people are constantly playing with people they have never met. If one person plays a certain type of groove and someone else ignores it completely then the music is infused with all kinds of tension, and not just the musical kind. It is far better to say- Ok, they are doing this, what can I do to fit in or take that somewhere new. No matter what they are presented with, a skilled improviser will find a way to work with it.