If it's calming and enjoyable, it can be a stim. NT stims can include rocking and nodding to music, singing, fidgetting, watching favorite videos, etc.
AS stims were noticed because a lot of them are 'different', like hand flapping and rocking without music and such. I think there is a stronger neurochemical reaction to certain stims for aspies, and a greater need to self-medicate. But I think NTs would be more even tempered if they learned to stim, too.
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"Yeah, I've always been myself, even when I was ill.
Only now I seem myself. And that's the important thing.
I have remembered how to seem."
-The Madness of King George