When we move ourselves our bodies are wired to feel that movement. We humans have beautifully intricate wiring (nerves) connecting feeling (sensory) with movement (motor).
Some movement feels good. And with that basic understanding, seeing children who repetitively moved in (sometimes unusual) ways, charter psychologists called this behavior self-stimulation. Early in Barbara’s career, therapists commonly shortened this to self-stim. Currently, parents like JoyMama and others who encounter or engage in self-stim have learned to call these behaviors ‘stimming’.
Stimming is part of the DSM definition of autism, though the definition does not use the word, perhaps because it is not technically-defined, nor even in the dictionary. "Stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements)." However, one can receive an autism diagnosis without meeting this particular criterion -- and stimming is associated with other conditions as well. Not everyone who stims has autism.
Repetitive movement is important for learning -- a mantra of Barbara’s if you read her blog regularly. But stimming does not fit the "important for learning" category in the same way, and can actually impede learning. Most educational/therapeutic references to stimming are made with negative overtones.
Stimming is sometimes described in words like these: unproductive, obsessive, obstructive, annoying, consuming. These perceptions of stimming are common among people who are observing it, such as parents, educators, bystanders.
In the autism community, some think that since stimming is part of the autism definition, reducing the stimming amounts to a reduction in the autism. Applied Behavior Analysis (ABA), an educational technique intended to reduce autistic behavior, is associated with that approach.
But another list of descriptors implies a different perspective on stimming: pleasurable, centering, meditative, regulating, communing. You are more likely to hear these from people who engage in stimming themselves.
Within this second perspective stimming is viewed as similar to what neurotypical individuals do to calm or entertain themselves: thumb-twiddling, pencil-tapping, leg-jiggling, even knitting. Stimming as regulating activity is seen as beneficial for helping people "keep it together," allowing them to block out negative or frightening input and keep from feeling overwhelmed.
One particularly thought-provoking insider-view comes from Amanda Baggs, an autistic self-advocate. In the first few minutes of the video "In My Language" below, she shares some of her "stereotyped and repetitive motor mannerisms," as the DSM would say. The latter part of the video gives Amanda's own translation of the meaning of her movements, using a voice synthesizer (Amanda's means of speech).
Families of children with autism struggle to find a balance between stimming and education. How does stimming interface or interfere with learning?
Does the behavior stand in the way of beneficial play? Learning is the work of childhood. And stimming can indeed impede learning when it consumes the play-time and energy, or turns educational objects into stim-objects.
JoyMama and Barbara offer the following ideas... in two categories. (This is a brief listing. To find out more, ask the professionals who work with your child.)
Reducing or preventing stimming
- regular (daily is best) ‘heavy work’ or strenuous activity/exercise
- consultation with a psychiatrist to rule-out or treat co-morbid mental illness
- consultation with a neurologist to rule-out or treat co-morbid seizures
- structured lifestyle
- discovering and avoiding an individual's triggers for stimming (for example, Joy stims on ribbons and strings. Her family sometimes "disappears" such objects when the focus needs to be elsewhere).

Using stimming to benefit the person or enhance their life
- stimming as reward-breaks between learning activities
- allowing some stim that can be done simultaneously with learning activity - maybe chewing a tube can help your child focus on a book or drawing
- use stimming during learning-play -- place a stimmy-toy into a tunnel to crawl & retrieve, take turns with tossing/catching a stimmy-object
- enter into the stimming-world together -- letting gravel run between your fingers and toes feels good!

Therapists have a saying that if you take away one stimming preference, another will develop in its place. Complete elimination of a stimming habit might be unrealistic, and not even desirable, depending on what function the stimming serves. Stimming-related goals, like all goals, are best seen in the context of the whole child.
Re-evaluate on a regular basis whether you are satisfied with the progress of your child or the effectiveness of the therapeutic and educational methods being used.
Update September 2010: There's an excellent insider-perspective post at Reports from a Resident Alien about stimming and its purposes and the sensory channels it affects.
Would you share approaches you have used to prevent or incorporate stimming in the life of your child?