I have been unable to track down the paper, but a recent study demonstrated that listener comprehension was higher when filler words were used during speech.<p>I think they are stigmatized because often they are used heavily by those who have no idea what they are taking about. But the fix is to know what you are talking about rather than to eliminate 'umm' from your vernacular. These pauses give your audience time to think, give your audience cues on what parts are important, and let you pull together your own thoughts.