Psychologists at Stanford and UC are apparently researching
the meaning of interjections like "uh" and "um". I can't comment on the research itself (since I haven't seen it), but an article on the work merely states the obvious. I'm wondering now: don't most people understand why they say "uh" and "um"?
When I was a kid, my father (a seasoned public speaker) explained that people use "uh" and "um" as placeholders to retain conversational control. In normal conversation, pauses of more than a breath usually signal "end of transmission", which means someone else gets to talk. When a speaker realizes she needs to think for a moment mid-sentence, and she's not willing to give up control yet, she interjects an "um" to stave off any potential respondents.
While this is natural (or at least common) in casual conversation, it's widely considered poor form to do the same in formal or public speech. It shows that you haven't thought your sentence through, and it makes you sound stupid.
The strange thing about the article is that, because they've "discovered" the role of these words, they seem to think the words have new legitimacy and value.
"In school we were taught not to use these phrases, but the fact is, everybody uses them," said Fox Tree, who says her high school debate teachers used to discourage the use of "um's" and "uh's." "So we think they must have a role."
The article stops short of suggesting that these words are good to use, but it seems like that's where they're leading. I hope the next generation of public speakers isn't taught to embrace these linguistic tools, intentionally punctuating its speech with dramatic "um"s. Listening to the State of the Union Address would be even more unbearable than it already is.