Self-stimulatory behavior, also known as stimming and self-stimulation, is the repetition of physical movements, sounds, words, or moving objects. These behaviors are common in individuals with developmental disabilities and most prevalent in those on the autism spectrum. Individuals diagnosed with sensory processing disorder are also known to potentially exhibit stimming behaviors. Stimming is considered a protective response to overstimulation, in which people calm themselves by blocking less predictable environmental stimuli, to which they have a heightened sensitivity. Another theory is that stimming is a way to relieve anxiety and other negative or heightened emotions. Stimming behaviors can consist of tactile, visual, auditory, olfactory, and vestibular stimming. Some common examples of stimming (sometimes called stims) include hand flapping, rocking, excessive or hard blinking, pacing, head banging, repeating noises or words, snapping fingers, and spinning objects. Stimming is almost always present in individuals on the autism spectrum, but does not necessarily indicate its presence. The biggest difference between autistic and non-autistic stimming is the type of stim and the quantity of stimming. In the Diagnostic and Statistical Manual of Mental Disorders, published by the American Psychiatric Association, stimming behavior is described as 'stereotyped and repetitive motor mannerisms' and listed as one of the symptoms of autism spectrum disorder. Different perspectives suggest that stimming involves both sensory and motor functions. Insufficiencies in these sensorimotor functions can result in stimming behaviors produced by the individual as a controllable response. Most individuals in the autistic community oppose attempts to reduce or eliminate stimming, as it is an important tool for self-regulation, and contend that attempts to stop people from stimming could be potentially harmful. However, stimming can sometimes be self-injurious, such as when it involves head-banging, hand-biting, excessive self-rubbing, and scratching. While it is difficult to stop stimming entirely, there are many ways to reduce time spent stimming and create safer stimming habits for an individual. Managing the sensory and emotional environment while increasing the amount of daily exercise can increase personal comfort levels of the individual, which may reduce the amount of time spent stimming. Things such as puzzles, fidget spinners, stress and fidget toys can also be used to help instill safe stimming habits.