Sometimes it's ok to trail off.

Ever notice when you ask certain people a question or attempt to siphon some feedback, they start to answer then mumble until incoherent? I've encountered this many times, even done it myself on occasion, I believe. What causes this? Is there some function in the brain that just spasms and this is a biproduct? There probably is no answer and there never will be. How do I know this? I studied Physical Attributes of the Cerebral Metatorso and hypothesized that this impossibility is not only impossible, but completely unhappenable. Furthermore, I don't eat fish. Perhaps this is because they swuss foob nuzzelt preed duba choofu snig mmmffns...