Updated: Aug 18, 2020
This post is part of our Sensory Simplified series. To see all posts in this series, click here. Please note that the information included is only a brief summary and is not intended to be nor is it a substitute for professional medical advice. If you have questions or concerns regarding your child's development, please consult a pediatric specialist.
The Sensory System
Just what on earth exactly is "sensory processing," and how does it play a role in development? We’ve created a blog series to lay it all out for you - so let’s start by covering the basics. As occupational therapy practitioners, this is one of our very favorite things to address, as it sets the foundation for so many other skills!
Sensory processing refers to the way our nervous systems receive messages from both people and our environment, and how we respond to them (behaviorally, emotionally or motor-wise). I’m a sucker for a good visual, so let’s throw in this flowchart:
Let’s walk through an example that you may experience. It’s the middle of the night, and you wake up in need of a glass of water. Navigating in the dark, you make your way carefully toward the kitchen. As you open the cabinet to retrieve a cup, you hear a loud crash behind you (here’s the input). Panic grips you. You scream, your heart pounds, and you turn around to face your threat (this is you processing and responding to that input). You make out the sight of your cat in the corner, proudly flicking his tail for having knocked over the broom that was propped up near the back door.
Phew. No threat after all. Albeit a little shaken, you pour your glass of water and make your way back to the room. Your body dismisses the idea of a threat, and you’re able to achieve your previous state of calm. You lay your head on your pillow and drift back to sleep (this is your ability to achieve regulation).
Now that we’ve got a general idea of how the processing system works, let’s discuss what senses we might receive our input from.
The sensory processing system of the brain is driven by eight senses. That’s right - we’ve got a few lesser known ones added in there! We receive our sensory input through these 8 channels: visual, auditory, olfactory, gustatory, tactile, proprioceptive, vestibular and interoception. While we will go more in depth in a later portion of this series, we will keep the descriptions condensed for now:
Visual: input that we receive through our visual system via our eyes
Auditory: input we receive through our ears
Olfactory: input received through the sensation of smell through our nose
Gustatory: input we receive through taste receptors in our mouth
Tactile: input we receive through the sensation of touch - whether that’s light touch, deep pressure, pain, vibration or temperature
Proprioceptive: input we receive through our bones and joints. This input let’s us gauge how hard we need to push to get the door open, and strongly relates to body awareness - like pointing to our nose even if our eyes are closed.
Vestibular: the system responsible for processing movement (are we going forwards or backwards?) and change in head position (are we upside down or right side up?)
Interoception: the awareness of internal sensations, such as when we are hungry or full, when we need to use the restroom, or that our stomach feels queasy.
Sensory processing difficulties happen when sensory information (e.g. sound, touch and movement) isn't organized into appropriate responses. Sometimes it's because a child has a heightened response to sensory input (over-responsive), or a dampened response to sensory input (under-responsive).
The H2o Analogy
We’ll use the widely adopted H2o analogy that offers a simple explanation of how the sensory processing system works. We all have a cup that holds the sensory input we experience from day to day. Back again with your regularly scheduled infographic:
With a neurotypical processing system, it's like filling a standard 8oz glass with water. It is coordinated or regulated - that glass doesn't overflow by blasting the amount of input we're putting in there, and we're not filling it drop by drop, either.
With a child who demonstrates over-responsive processing, it's like they have a smaller cup. Input that comes in is not regulated or coordinated - it's more like using a firehose to fill a shot glass. It's too much all at once, with more consistently coming in before the child even has a chance to process, respond or react to what's already being experienced. We often see behaviors that allude to discomfort or overstimulation with these children (retreating, crying, going into a "fight or flight" mode).
Kids who experience under-responsiveness can react in one of two ways. They may passively under-respond, which is similar to using an eyedropper to fill a pitcher. The amount of input doesn't match the need of the child, and we may see behaviors such as appearing disengaged or disinterested. They may require a lot more movement, interaction or input to socially participate.
They may also actively under-respond, which is similar to having water poured into a styrofoam cup - except that cup happens to have holes at the bottom. That cup is never quite able to achieve the level it needs to maintain a regulated state. Children who actively under-respond are often referred to as "sensory seekers." They may be described as constantly “on the go,” having difficulty with maintaining personal space or a calm body.
Children experiencing sensory processing difficulties may appear more inwardly focused, as they're more concerned with avoiding the input that is overwhelming to them, or getting the input that they continue to crave. They may seem to have difficulty with focusing on anything else.
If we have a regulated sensory system, we're able to maintain a calm and "ready to learn" state. We may have a distracting noise in the background, but we can filter it out. We may feel an itch at the back of our neck, but we scratch it or ignore it and carry on. We may be feeling restless, but we'll get a good stretch in and get back to work. We're able to properly regulate the things we see, feel and hear, and that allows us to be outwardly focused and engaged with the people and things around us.