Sudden head lifting - non aggressive arguments?

[BlueBird]

All of my pigs at some point have a moment when they are sitting close to another herd member there is a half second pause then one lifts their head as if the other lunged at them. I'm assuming it is the result of them losing some non-verbal, non-aggressive fight that I'm unaware of as it often happens at the breakfast bowl but not always. I'm not sure what it means. I'm also not sure who is the winner as the non-head raiser often carries on regardless. It was just a behaviour I was curious of and couldn't work out.

 

[Eriathwen]

Judging by my own pigs behaviour, the less dominant piggy is the one whose head is higher up. I suppose exposing the throat is a submissive behaviour maybe? Or allowing the more dominant to sniff your chin/raise your head?
It's quite a common occurance within my herd of 7 although I rarely see it in my pairs.