Of course, not everyone is saying "um," "uh" or "well" when hesitated or for some reason are afraid or embarrassed to express their opinion. Everything depends on the language. For example, the Chinese media in this case, pronounced «zhege», which translates roughly as "it." In Russian, we usually drink "um" or "uh" or "ah", or other similar vocalizations, to interpret that letter using the already complicated. The sounds of "um" and "uh" contain what linguists usually called schwa. It sounds very simple for our vocal apparatus.
We realize it or not, as a rule, the two talking to each other person speak at a time. If a person decides that now it was his turn to speak, he does it. If at this moment all the other - listening. Any dialogue is like a ping-pong: inevitable short periods of silence - people take a pause to give the floor to the other party. But sometimes before the next phrase to formulate thoughts need a little more time, and then the one whose turn it is to talk, use the "uh" or "nuuu ..." or something like that, to give the other person to understand. It's just a subconscious phonetic signal: "Shut up now, I have not finished».