One of the guys I follow is Graham over at My Views on Science and News who pulls up articles from science news sites. A post he recently made was about a a study concerning persuasive speech conducted at the University of Michigan. I got really excited because I thought the science direct article would mention why the disfluency "um" was in the title. It wasn't, but it peaked my interest and now I want to write about it.
Filled pauses, or disfluencies (think uh um ah thee... etc.) can give us inferences in what the speaker is saying. There's many different examples of this but my favorite is one the was shown in the paper If You Say thee uh You Are Describing Something Hard. Which makes the argument that disfluencies are encountered because the speaker is planing a new utterance, describing something difficult, or is being distracted. I cannot directly link it to you, but if you have a college or university log in you might have access to it on one of the journal websites. You can find the full citation at the bottom of this page.
Here's how the experiment worked. If I take a native English speaker and hook them up to an eye tracking machine, while showing them a picture like this on a computer screen:
And they then hear LOOK AT THE RED UH...
they are most likely to look at that red Chinese looking character in the top corner (for the sake of this image it is a Chinese character). Being a native English speaker, the Chinese symbol would be foreign and different to them. This study suggests that disfluencies refer to unexpected objects.
The study goes on to show results for studies in which people were asked to click on objects, and also includes some ERP data. If you're interested I have the citation below:
Arnold, Jennifer E., Carla L. Hudson Kam, and Michael K. Tanenhaus. "If You Say Thee Uh You Are Describing Something Hard: The On-line Attribution of Disfluency during Reference Comprehension." Journal of Experimental Psychology: Learning, Memory, and Cognition 33.5 (2007): 914-30. Print.