Stims are sensory input that is pleasurable and calms us down. Stims may cause certain chemicals to be released in our brains. I think it's a way of self-medicating the brain's natural anti-anxiety chemicals.
Stims sometimes blend into fidgeting, and about 20% of NTs also stim.
Some classic stims are rocking back and forth, moving your hands in strange, contorted ways, pacing, and walking on tip-toe.
Rocking and bobbing ones head to music is probably a stim that is shared with most NTs.
Stims are semi-voluntary (not compulsive or reflex), and can be altered into forms that don't disturb other people.
Stims are good.
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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