Take a look at this. Attack on Titan [Possible spoilers for you]

This person on tumblr made a post showing when xxxxx and eren are training you'll see she is holding her neck.

Perhaps this is out of habit?
http://you-put-your-left-armin.tumblr.com/post/59872811587/i-want-you-to-take-a-look-at-something-i-noticed