silence

This week we discussed the role of extralinguistic communication in creating an equal opportunity for members of a conversation to have the floor. We discussed several models for how silence in conversation is negotiated by the members of the group, including deferential nodding that maximizes the amount of communication even during silence and an aversion to silence that leads some to finish a speaker's sentence.
Personally, I can identify with the method of providing feedback in silences that let the speaker know I am listening. That is, when acting as a listener, I feel the need to fill in the silences left by the speaker with affirmations such as "uh huh" or "oh yeah?" This not only eliminates silences, but also reaffirms the status of the speaker has having the floor. I am communicating that I am listening and understanding the story, while still maintaining my deference of the floor to the speaker.
Do you think these methods are truly cultural? Or can anyone provide exceptions (i.e. americans who nod and smile)? What are your conversational styles?