I noticed this before they instituted the "random arrow iPad." I'm not sure about their level of social aptitude though. I got sent to the quick screening line 5 or 6 times in a row, but the people I saw flagged for the slower screening were people who I thought looked calm but less whitebread than me. People with their hair dyed blue, holes in the knees, etc.

I think the person who is actually reading people is the person who checks your ID and boarding pass. Though honestly I think that process would be pretty easy to fool either way.