Children can be born hypersensitive, or hyposensitive, in varying degrees in any of their five senses. An example of an hypersensitive child is one that complains that her clothes hurt or itch her, or that the light is too bright. Another example of hypersensivity is someone who does not like to be touched or caressed, or someone who won't look directly into the eyes of another person. An example of a child or adult with hyposensivity is one who throws himself into a wall in order to get a sense of his body.
Sensory integration generally tends to affect three over-riding systems inside the body: tactile (touch), vestibular (balance-located in the ears) and proprioceptive (where the body is). These may complicate the picture, more than a simple sensory sensitivity of hearing or sight, which is concerned with processing in the brain. A proprioceptive sensitivity may cause a person to not know the boundaries in her body, like where the beginning and end of her arms are, or where they are in relation to the rest. Tactile sensitivities may be manifested in many different ways. Someone who has a vestibular sensitivity may really like roller coaster rides because of their centrifugal force. It gives extreme stimulation to their vestibular system.
Sensory integration dysfunction is a common symptom of Autism. Often an autistic child receives too much information through his senses, and in order to turn down the volume, he avoids people, noises and bright lights. The autistic child has not learned to integrate and modulate the information from his five senses.
Grandin reports in her book (Thinking in Pictures) the results of a survey about sensory integration in a relatively small population with Autism Spectrum Disorder from one centre.
"A survey of sensory problems in 30 adults and children was conducted by Neil Walker and Margaret Whelan from the Geneva Centre in Toronto. Eighty percent reported hypersensivity to touch. Eighty-seven percent reported hypersensivity to sound. Eighty-six percent had problems with vision. However, thirty percent reported taste or smell sensivities."