"UH, THE COLLEGE DAUGHTER WILL LOVE THIS". Harper's Index reports the average number of "uhs" used by college science professors while lecturing is 1.39 per minute. The average number used by college humanities professors is, uh, 4.85 per minute. I have made the College Daughter paranoid about this, as it is a pet peeve of mine. I think I indicates you can speak faster than you can think. That is especially bad if you come from West Texas, where speaking is painfully slow. (Our poor computer suffers this same fate. I can type faster than it can process, so it periodically locks up so I cannot type any more. I had to take a break, for example, between speak and faster and go get a drink.)
You would like to think a college professor could think as fast as he could speak, since they are educating our young people. It could be that they really just do not have that much to say and are killing time.
Preachers do this at times also. Have you ever sat through a sermon when the preacher clearly preached his sermon in 15 minutes, but did not want to quit? So, he just preaches it over again.
So you see, it is a good principle all around: only speak when you have something to say. Otherwise, let the silence speak for itself. You will find it does not hurt anyone, and you will appear much more intelligent waiting out the silence that filling the air with "uh".
And breathe through your nose.