I was reading about this and apparently it can be a neurodiverse trait, I've grown out of it a bit now but I remember when I was a child I would laugh if someone was trying to teach me something one on one, like my mum helping with homework or the teacher explaining something just to me, also I remember laughing when getting told off by my parents (which wasn't very often I was quite a good child) and laughing uncontrollably when my dad smacked my bum once!
at secondary school if some one in the class was messing around and everyone was laughing, the teacher would say "stop laughing it encourages them" but I wouldn't be able to stop when the rest of the class could, I would struggle to keep it in and hide behind my books or bag trying desperately to stop
I still laugh when my husbands cross or deadly serious because he's not like it very often, I find it weird and amusing
Any one else?