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Sensory System 

All information our brain takes in is sensory in nature. If brains attended to 100% of the information coming it, we would be constantly overwhelmed. Because of this, humans come with filtering systems to decrease the amount of information coming in. The filtering system of neurodivergent brains can be different from those of neurotypical/allistic brains in two ways:
 

  1. The filter lets in comparatively more sensory information

  2. The filter lets in comparatively less sensory information

Visually, we can view this filter as a mesh screen. The screen in the allistic filter lets in a pre-determined amount of sensory info (A). The neurodivergent screen can be: (A) the same as the allistic filter; (B) finer, in that it has smaller holes and lets in less info; or (C) coarser, in that it has larger holes and lets in more info

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For example, the allistic filter lets in a predetermined amount of sensory info from the environment, as demonstrated in the figure  ->


 

Depending on the person, some neurodivergent (ND) individuals may have a filter that lets in less information than allistic folks, as seen in the middle picture ->


 

In contrast, other ND individuals may let in more sensory information than allistic folks, as seen in the bottom picture -> 

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ND filters can be thought of as Hypo versus Hyper depending on how much sensory info they let in to be processed 

  1. The filter lets in less sensory information = hyposensitive

  2. The filter that lets in more sensory information = hypersensitive


What do these filtering systems look like?  Let’s use the auditory (sounds) system to illustrate:

 

Hyposensitive filters look like

  1. Less aware of sensory info(e.g., may not hear noise)

  2. Needs more sensory info (e.g., need louder or repetitive noises) 

  3. Does not or is slower to respond to info (e.g., may need more prompts) 

  4. May seek out sensory info (e.g., make noises)
     

Hypersensitive filters look like

  1. A small amount of info is activating (e.g., may hear noises others cannot)

  2. May go into fight or flight mode (e.g., overwhelmed or ‘meltdown’)

  3. Ongoing info may be uncomfortable (e.g., repetitive noise is grating)

  4. May avoid out sensory info (e.g., stay away from areas with certain noises)

YET, there is more complexity at work here.

 

Each sensory system may have its own filter. So, one could be either hyper- or hypo-sensitive across each domain. When we think of sensory systems, the 5 senses come to mind: sight, sound, touch, taste, and smell. Yet, the number of sensory systems we have is higher, with some arguing that we have 8, 21, or even 53 different senses. That’s complex!

The 5 we are taught in elementary school was first described by Aristotle (in De Anima) but most neurologists suggest there are 8 senses. The additional 3 senses include interoception (sense of internal systems, e.g., hunger), vestibular (sense of balance), and proprioception (sense of body awareness). The senses can be even further categorized if you like all the differences and details (for example, within interoception, we could break that down into senses of hunger, thirst, temperature, pain) (Francis, 2020).

Let’s explore how each of these sensory systems can be impacted by a hyper- or hypo-sensitive filter

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Hyposensitive :

  • Can struggle to find people in crowded place (e.g., school yard)

  • Can struggle to find something in busy backgrounds (e.g., messy room)

  • Can struggle to keep track of where they are when reading (e.g., next line)

  • May like watching things move across their vision (e.g., flicking fingers in front of eyes)

  • May like flashing lights or other repetitive visual stimuli (e.g., lava lamp)

  • May have poor depth perception

 

Hypersensitive

  • Sensitive to bright light, fluorescent lights, sunlight, or certain colours

  • Prefer dimly light spaces

  • Overwhelmed by visual changes in environment (e.g., moving furniture around)

  • May use peripheral vision to look at things (limits amount of visual info coming in)

  • May blink a lot

  • May need complete darkness while trying to sleep

Screenshot 2023-08-30 at 1.27.18 PM.png

Hyposensitive:

  • May not respond to name or instructions

  • May zone out (e.g., look like they are daydreaming)

  • Can struggle to remember what was said (e.g., may say ‘what’ a lot)

  • May not be able to tell the difference between similar sounds 

  • May make noises (be loud, bang objects together, hum, or sing)

  • May tap or bang things to hear the sound

  • May turn TV or music up very loudly

Hypersensitive: 

  • May have difficulty ignoring sounds in the background (e.g., talking in another room)

  • May hear sounds that others cannot hear (e.g., high or low frequencies)

  • May may own sounds to block out sounds they do not like 

  • May struggle in rooms with a lot of people or sound and want to leave

  • May startle when hear sudden or loud noises

Screenshot 2023-08-30 at 1.27.22 PM.png

Hyposensitive:

  • May be unaware of light touches (e.g., need firm pressure to ‘feel’ touch)

  • May be more aggressive in the physical contact with others 

  • May drop items due to differences in holding (e.g., may hold too lightly)

  • May use mouth to explore objects (e.g., holding things in mouth)

  • May enjoy messy play (e.g., painting, clay)

  • May seek out certain textures (e.g., rough or smooth)

  • May like tight clothing 

Hypersensitive: 

  • May not like being touched, especially if unexpected

  • Hair brushing may be uncomfortable

  • May not like certain fabrics or tags on skin

  • May not like getting dirty (e.g., sticky or muddy)

  • May walk on toes or refuse to walk on certain surfaces

  • May not like certain food textures

  • May not like wet textures (including face washing)

Screenshot 2023-08-30 at 1.27.26 PM.png

Hyposensitive:

  • May like to put things in their mouth

  • May seek out strong flavours

  • May lick things 

  • May crave certain flavors

 

Hypersensitive: 

  • May not like certain textures to tastes 

  • May prefer a predictable diet

  • May prefer foods that are the same each time (e.g., crackers over fruit)

  • May find flavourful food overwhelming

Screenshot 2023-08-30 at 1.27.29 PM.png

Hyposensitive:

  • May not notice smells

  • May prefer strong smells and tastes 

  • May like to smell everything

  • May seek out strong smells 

 

Hypersensitive: 

  • May have a strong smell intolerance

  • May avoid foods with certain smells 

  • May prefer tasteless foods

  • May gag or become upset at strong smells

  • May have a restricted diet

Screenshot 2023-08-30 at 1.27.34 PM.png

Hyposensitive :

  • May have little reaction to pain

  • May not notice changes in temperature

  • May not feel hunger or thirst

  • May find it difficult to understand what they are feelin

 

Hypersensitive: 

  • May dislike certain temperatures (too warm or too cold?

  • May notice small changes in physiological system (changes in heartbeat or breathing)

  • May feel pain deeply

  • May feel emotions deeply (e.g., “too sensitive”)

Screenshot 2023-08-30 at 1.27.39 PM.png

Hyposensitive:

  • May seek out movement (e.g., spinning, bouncing, shake head, etc)

  • May be a thrill seeker (e.g., love amusement park rides)

  • May not get dizzy

  • May like hanging upside down

  • May like to rock back and forth

Hypersensitive: 

  • May avoid swinging, spinning, or sliding

  • May have a fear of heights

  • May get motion sickness

  • May lose balance 

Screenshot 2023-08-30 at 1.27.44 PM.png

Hyposensitive:

  • May appear clumsy (e.g., tripping over things or banging into objects) 

  • May move around a lot

  • May like to be wrapped up in blankets or tucked tightly in bed

  • May fidget quite a bit

  • May have trouble balancing

  • May prefer tight clothes

 

Hypersensitive

  • May prefer to remain seated 

  • May lean against things or people

  • May have difficultly with fine motor skills (e.g., holding a pencil, picking up small items) 

Role of Senses in Overwhelm

When considering how the 8 senses play a role in making our way through the world, we can see how being hyper-sensitive to even one sense can cause distress in one’s life. Imagine if you were hypersensitive to two or more senses, and how they additive effects may lead to overwhelming feelings, meltdowns, or burnouts

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