Exactly. Having seen pg speak many times, I can say that his 'umms' actually give you the feeling that he is thinking hard about the topic versus just rattling

Exactly. Having seen pg speak many times, I can say that his 'umms' actually give you the feeling that he is thinking hard about the topic versus just rattling out some predetermined idea. As I stated in my earlier comment, I think 'umms' can actually help the speaker establish genuineness with the audience.