Reaching back...decades ago when I was in anthropology class (I don't believe you guys never heard of this stuff - the whole complex cultural norms in conversation) one of the topics was about intercultural communication.

People in different cultures converse differently, which can at time be disconcerting and be misunderstood. Things like personal space. Cultural norms about when people conversing look at each other and look away. Gesture.

There was a story about a US ambassador to Brazil (I think. Somewhere in Latin America anyway.) The Brazilian, trying to be welcoming, kept approaching the ambassador and invading his personal space (a cultural norm among white North Americans). The ambassador felt uncomfortable (intimidated?) and kept backing away. The Brazilian, thinking that the ambassador wasn't getting the good vibes he was trying to express, kept closing in, and so on. The way I remember it, the two of them did this dance around a table a few times.

We were given an assignment. Describe the ways white and black American males converse differently. We all missed one glaringly obvious trait: when two white males converse, the listener watches the speaker and the speaker gave no more than an odd glance to the listener. Who looked at whom reversed when the other spoke. Among black males, the opposite was true. The speaker stared at the listener, the listener gazed elsewhere. I can speak to this behavior myself, having repeatedly observed it (though this may have been a temporary faddish mannerism - I hardly see it at all nowadays.)

Obama has a habit when he speaks of filling his pauses with an, "uhhhhh". He exhales when he does this, which signals that he's lost the train of thought. Were he inhaling, it would signal that he has a firm grip on the idea, but that he needs to marshall the proper phrasing. And appears much more sure of himself.

I'm usually pretty good at spotting emotional reactions in myself. Lemme look. . . .

"It Can't Be Just About Us"
--Frank Schnittger, ETian Extraordinaire