I think certain gestures look funny (funniest one is nodding in my opinion), so when I'm very bored I start paying attention to that. However, nowadays I tend to suppress that and focus on other things because otherwise I have to fight the urge to laugh and I don't want to offend the person talking to me if I suddenly can't hold it anymore. Usually it's enough to just spectate one funny gesture and I'm no more bored and have a hard time staying calm.
But when I'm just bored my thoughts just start to drift off which requires more concentration to be able to follow the conversation.
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Diagnosed with Aspergers.
BSP-errors are awesome.