What are the components of Sensory Processing Disorder (SPD)?
Lucy Miller (2014) has identified three parts to SPD:
SPD – Sensory modulation
The first component of Sensory Processing Disorder is modulation. Sensory modulation is the ability to produce a behaviour and/or response that matches the nature and intensity of the sensory input and environment (Lucy Miller 2014 p.14). This means that the response to the sensory messages is what would be expected; it would match what had occurred. The responses of children and adults with SPD often do not match the sensory message or environment. There can be challenges with some or all senses. Sensory issues related to modulation difficulties can include:
- Over-responsivity, or sensitivity to sensory input;
- Under-responsivity or not responding to sensory input;
- Craving or seeking out extra sensory input.
I discuss these responses in more depth on this page: signs and symptoms of sensory issues.
Sensory modulation is also called sensory reactivity by some therapists. These therapists will consider hypo and hyper reactivity. So, a slower (hypo) reaction. Or, a bigger (hyper) reaction. Reactivity is being used to bring terminology inline with the 2013 update of the autism diagnostic criteria in a book called the DSM-V.
SPD – Sensory discrimination
The second component of SPD is discrimination. Sensory discrimination is knowing what the sensory input was, where it happened and how intense it was. So, if you stub your toe your brain should be able to figure out (or discriminate) which toe it was and how hard you banged it. When you put your hand into your bag to find your keys, your touch sense can identify (or discriminate) the feeling of your phone and wallet from your keys. When you open a pot of yogurt your proprioceptive system pulls the lid with enough force to open it but hopefully not spill it everywhere! These are examples of discrimination.
Some therapists will use the term sensory perception when they are talking about sensory discrimination.
SPD – Sensory-based movement
The third component of SPD is sensory-based movement. In this section, Miller (2041) includes praxis and posture. Praxis is the ability to plan and organise new and novel movements. It is exceptionally important for learning new skills. People are often more familiar with the term dyspraxia which means difficulty with praxis or planning. Posture relates to postural control, balance and stability.
You can read more about how these sensory processing challenges could look for different children on our signs and symptoms of sensory issues page. If you wanted to learn more about dyspraxia you can read our post – Dyspraxia it’s more than clumsiness.