Many kids with autism and Aspergers have unusual reactions to sensory experiences (i.e., experiences related to the senses of touch, hearing, vision, smell, and taste). About 40 per cent of kids with autism have some abnormality of sensory sensitivity. There is now evidence to suggest that the incidence may be the same for Aspergers. The senses of touch and hearing are most commonly affected; certain kinds of touch, especially light pressure, and certain sounds may be experienced as intolerable. This difficulty is known as sensory defensiveness. Interestingly, while kids with autism and Aspergers are usually hypersensitive to sensory input, at other times they may be under-reactive, particularly to pain and changes in temperature. It is not uncommon for over-reactivity and under-reactivity to co-exist in the same individual. The following examples illustrate these points.
One child became so agitated by the sound of the vacuum (over-reactive) that every time the house cleaners arrived, he attempted to push them out the door. Some kids react to sounds others do not even perceive to be present (over-reactive); a common example of this is fluorescent lights which many individuals with Aspergers find extremely disturbing. Kids have been known to sleep between the mattress and the box-spring (under-reactive), apparently craving the sensory input.
A number of adults with autism or Aspergers who speak and write about the nature of their own experience stress the overwhelming importance of sensory issues to their functioning. Temple Grandin, arguably the most famous person with autism in the world, holds a doctorate in animal studies and teaches at Colorado State University. She has developed a "squeeze machine", a kind of holding device that allows her to control the amount of pressure exerted on her body. She talks about the calming effect this device has on her when she feels stressed.
Similarly, many kids with autism spectrum disorder crave swinging, apparently finding it soothing and organizing to their nervous systems.
Certain clinicians, for example, Stanley Greenspan, M.D., consider sensory difficulties of overriding importance in developmental disorders and believe a number of the symptoms occur in response to the underlying sensory issues. For example, it is no wonder a young kid withdraws if he is overwhelmed by the touch of his parents or if he finds loud noises unbearable.