Ayres introduced the concepts of tactile defensiveness (for tactile sense), gravitational insecurity (vestibular system), and postural insecurity (proprioception). She defined tactile defensiveness as avoiding or negative reactions to non-noxious tactile stimuli and as an imbalance between discriminative and protective sensory processing. Tactile defensiveness is manifested in 'fright, flight, or fight' response or reaction.
However, the concept of defensiveness in the context of SID seems to be misleading as it implies the reaction (i.e. behavior caused by something) rather than the cause(s) of this reaction.
Gradually, the shift from sensory defensiveness to sensory modulation problems (a person's threshold for responsiveness to sensation) was made. Probably, that is why, though OT researchers still write about tactile defensiveness, while describing problems in other sensory modalities they prefer to use 'hypersensitivity' rather than 'visual defensiveness'/'auditory defensiveness', etc. It seems quite logical, as hypersensitivity experienced by the individual causes defensiveness (reaction/behavior).
According to Sensory Integration International, some signs of SID are:
- Oversensitivity to touch, movement, sights, or sounds
- Underreactivity to touch, movement, sights, or sounds
- Tendency to be easily distracted
- Social and/or emotional problems
- Activity level that is unusually high or unusually low
- Clumsiness or apparent carelessness
- Impulsive, lacking in self-control
- Difficulty making transitions from one situation to another
- Inability to unwind or calm self
- Poor self concept
- Delays in speech, language, or motor skills
- Delays in academic achievement
These signs are often complemented with more specific symptoms from all sensory modalities and often coincide with the symptoms of Central Auditory Processing (CAPD) and Scotopic Sensitivity/Irlen Syndrome.
At present there are two distinct views on the 'status' of SID. Some authors argue that numerous psychological, psychiatric and neurological disorders such as schizophrenia, depression, ADHD, autism, etc. appear the same as SID, and that many symptoms of SID look like symptoms of other common disabilities, making it difficult to differentiate one difficulty from another. Others think that referring to the cluster of SI problems as a disorder may be premature as SID has not been identified as having universal and persistent features that are distinct from other established disorders. One can make some suggestions. Instead of trying to embrace all sensory and information processing disorders under one umbrella term, wouldn't it better to distinguish specific patterns of sensory perceptual problems in different 'established disorders'? For instance, though sensory perceptual problems have not been incorporated into diagnostic classifications, very specific and easy-to-describe unusual responses to sensory stimuli have been reported in most autistic children when they are observed prior to 6 years of age or when their parents are questioned about specific behaviors (Ornitz). It would be useful to compile specific patterns of sensory perceptual problems for different developmental disorders in order to find out whether there are differences in their manifestations.
