Avengilante wrote:
Stimming is a repetitive MOTION, engaged in to alleviate stress. Its not a nervous habit. Rocking, swaying, hand flapping, pacing are stims. Hair twisting, nail biting, etc are not.
Wikipedia wrote:
Stimming is a repetitive body movement that is hypothesized to stimulate one or more senses. The term is shorthand for self-stimulation. Repetitive movement, or stereotypy, is often referred to as stimming under the hypothesis that it has a function related to sensory input.[1]
Autistic individuals are sometimes known to stim. In some cases it helps with thinking or concentration while in others it can assist in bleeding off excessive excitement about something
Wikipedia is only one source for information, but I would point out that the quote you give actually mentions 'stereotypy', under Wikipedia entry for Stereotypy it includes the following (under animals, but point remains);
Wikipedia wrote:
Examples of stereotypical behaviors include pacing, rocking, swimming in circles, excessive sleeping, self-mutilation (including feather picking and excessive grooming)
Nail biting would come under self-mutilation, it's no different to picking at skin as a stim. I would argue that it's a behaviour engaged in to relieve stress (just because many people have it as a nervous habit doesn't mean it can't also be a stim), and it can be a repetitive motion too as a repetitive picking, biting or scraping the tip of the nail with teeth. Particularly it's a behaviour done to stimulate senses - taste and touch - in my case I bite my nails in place of tapping my fingers during time of stress, but it is primarily about oral stimulation...the same as during nail biting I will also tap my fingers upon my bottom lip, rub my fingers over my lips, or put my lips to the tip of the nail when they're long and cooler at the tips.
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