Not everyone says "um", "er" or "ah" when they hesitate while speaking. It depends upon the language.
For example, speakers of Mandarin Chinese often say"zhege" which roughly translates as “this”. In English we say "um", "er", "ah", or other vocalisations for reasons that linguists are not entirely sure about. "Um", "er", and “ah” contain what linguists call "neutral vowel sounds" making them among the easiest sounds to make.
Watching all the talk shows here in the Philippines, I think ummm, errrr, and ahhhh are part of the showbiz lingo here in the ummm... Philippines
