We are all aware of the first five senses; sight, touch, taste, hearing and smell; however, most of us are unaware of that there are another two senses. We all have Proprioceptive and Vestibular senses. The Proprioceptive sense deals with the internal feedback we receive regarding the location of our muscles, tendons and joints. The Vestibular sense deals with our location in our environment and is stimulated by the movement of the head and the input from gravity as well as the other senses.
In most people, we are able to understand and in some ways filter the input from all seven senses. In a lot of children with ASD, they are hypo (under) or hyper (over) sensitive to the input in the senses. This can mean that they are either not able to obtain any reaction to the sensory input, or alternatively they have too much reaction. To make it more confusing, children with ASD (and Sensory Integration Disorder), can be both hypo-sensitive in one or more of the senses AS well as being hyper-sensitive in others. It therefore requires a large amount of observation to understand which of the senses the child is having difficulty processing.
Many students with ASD have visual or auditory perception problems. There are also children with ASD that crave deep touch but are disturbed by a unannounced light touch. It is common for children who react defensively to light touch to actually have an under-sensitivity to pain. Children with proprioceptive abnormalities have difficulties judging how much force or pressure to apply when picking up objects or when they have to hold something. Vestibular system issues can lead to a phenomenon known as gravitational insecurity where children feel insecure when they do not have their feet placed firmly on the floor or stable surface. Alternatively vestibular hypo-senstivity will mean the child will hardly ever become dizzy. Difficulties in the proprioceptive, vestibular and tactile senses can create motor planning issues.
A table showing the indicators of being hyper or hypo senstive in these senses can be found here:
A video showing what it can be like for a child viewing the world with Auditory and Visual sensory issues can be found here:
Try watching the video and then imagine living with this day in and day out.
One of the important factors to remember is that abnormal sensory input leads to abnormal motor, language or emotional output. As with Information processing, executive function and "Theory of Mind", Fatigue, Anxiety, comfort level, motivation and trust all have an external influence. Often sensory issues are ignored or not identified and therefore the abnormal motor output is seen as a behavioural issue instead of sensory issue. With children with ASD (or SPD) you need to look beyond the external behaviour and examine the sensory issues behind it.
If there are Sensory Integration difficulties, then you will need to create a "sensory diet" with an Occupational Therapist. There are few books which deal with creating a "sensory diet". You will find them in my book-list. "The Out-of-sync child has fun" and "Building Bridges" are the ones that have been recommended to me.