The TSA spend $1B in 2013 on 'behavioral detection'. Below a part of the list.
I don't have 'a bobbing adam's apple', perhaps that's the reason why I didn't have problems entering the US last summer. I expected to have a lot of delays, my daughter and me were making fun of it and agreed to not get impatient.
The reason? If I enter a festival, a themepark, a border, an airport et cetera here in Europe they always take me aside for a more thorough check. I once read an article on the rules here in the Netherlands. Security and police check people who act and look not like the mass. Conclusion: That's me!
This proofs also that different countries have different rules.