I personally think it is unfortunate that many NDs have so easily accepted that stimming is “just” the autistic version of fidgeting, because as I see it, the difference is actually neurobiological.
The problem starts with wrongly associating stimming with anxiety relief, concentration and other similar, secondary types of human behaviour, because while fidgeting does certainly and most of the time unconsciously assist with especially concentration or stress relief, stimming, as a behaviour sequence mostly specific to autistic conditions, is actually a primary neurobiological undertaking, with a very clear role in an autistic individual’s life.
If an autistic person would observe themselves while stimming, they would notice that the stimming activity they are engaged in, requires their dedicated attention, through which the stimming routine is carried out according to a deeply ingrained routine. Stimming is as important as any other autistic routine, probably even more important, because while other routines, e.g. replacing the toothpaste tub in the same place and at the same angle after each use (as the routine’s objective), has the toothpaste tub as its object, stimming’s object & objective are identical, permeating actually the person engaged in stimming. While stimming, the autistic individuals employ all their task specific dedicated senses. Now this wouldn’t be unusual, if the respective sense(s) would be analysed, evaluated and responded to, as usually in NT cases, by specific areas of the brain. But since autistic brains are thought to analyse, evaluate and respond through the entire cerebral cortex to all/any stimuli (this being the very reason of sensory overload), an overlapping of sensory receptor(s) and stimulus happens, with the stimulus remaining nevertheless auxiliary in achieving the desired stimulation, with the brain and its response as the ultimate goal. Let me exemplify.
You sit in your car, and start drumming on your steering wheel, knee, door armrest, etc. But this is not your usual drumming on your favourite tune, or unconsciously fidgeting with your fingers while looking at the red light. No, it’s none of these, but your well known, always the same rhythmic sequence, the perfect product of your autistic brain’s systemising function, which combines not only the same audible rhythm, but the sensory impulses received by the same areas of your fingers’ skin from the soft, always the same areas of the wheel, the soft rotating movement of your wrists, dwelling always on the same areas of your legs, while your vision has switched to enhanced peripheral vision, seeing the beginning and the end of your journey, your next WP post and the irregular helix of steam arising from your next coffee, just to name a few…
Having said that, I hope I’ve answered any unasked question about “autistic fidgeting”, which yes, it is certainly possible, but in my opinion never to be mistaken for stimming.
Stimming is like the magnificent wing flapping of a hummingbird, in which all its neurobiology is implicated, which defines its entire being.
What about self-harmful, injurious repetitive actions, one may ask?
According to Lorna Wing (The Autistic Spectrum, New Updated Edition, p.45, 1996), a self-injurious repetitive action such as self-biting, head-banging, etc, “more often […] is a response to distress, anger or frustration […] but self-injury can be a repetitive habit in someone who has no other way of occupying themselves”.
In light of the above, having also witnessed this type of behaviour in non-autistic children and adults with congenital or acquired learning disabilities or limitations, also in animals confined to very small places, I would suggest that such behaviour isn’t necessarily autistic, but a physiological response to pathological stimuli, and therefore shouldn’t be necessarily considered stimming, except in cases of severe learning disabilities when according to Wing “self-injury can be[come] a repetitive habit in someone who has no other way of occupying themselves”. In such cases, protective gear and pharmacotherapy are considered as means of ensuring that the individuals themselves and their environment are protected as much as possible from harm, while maintaining the highest achievable degree of dignity and autonomy.