Sensory Processing Disorder Unveiled and Explained

In this post, I will explain what sensory processing disorder (SPD) is in simple, everyday terms. My hope is to bring insight and understanding to this very complex, often confusing, condition that many children have. About 1 in 20 children have SPD.

Sensory Processing Disorder Unveiled
Sensory Processing Disorder Unveiled

What is sensory processing disorder?

Sensory processing disorder is diagnosed in children who display difficulty with organizing (processing) and responding (reacting) to information that is received from our senses. Sensory processing is a neurobiological process that occurs at every moment of the day.  We all need to process and react to sensory information at all times.  Neurotypically developed children and adults process sensory input spontaneously.  Like breathing, we don’t need to think about how to do it, we just do.  Children with SPD are challenged by processing sensory input resulting in atypical or unexpected responses.  Some children are over-responsive or hypersensitive to sensory input.  Some children with SPD are under-responsive or hyposensitive.  Some children with SPD are a combination of both.

What is sensory input? 

Sensory input is the information that we take in through our senses.  What we see, what we hear, what we smell, what we touch, what we taste, even what we feel happening inside our bodies (hunger, pain, etc.)  Children with SPD can experience varying degrees of over and under-responsive behavior.  Sometimes the response may be subtle and does not interrupt day-to-day functions.  On the other hand, some sensory experiences may lead up to what we call  “sensory overload” or a feeling of being overwhelmed and upset.  Sensory overload may often be mistaken for a temper tantrum because children may scream or hit themselves or others, etc.  Oftentimes, however, children are reacting to a major sensory event or a build-up of several minor sensory events.  They do not know how to process the information from their environment and appropriately react to it, resulting in a meltdown.   Sensory overload may be caused by one or a combination of common triggers:

  • loud, unexpected noises
  • bright or flickering strobe lights
  • scratchy tags on clothing
  • scratchy clothing like wool sweaters
  • certain textures and/or scents of food
  • light touch and/or unexpected light touch
  • needing to move when expected to sit still
  • ambient scents or odors
  • tactile defensiveness
  • gravitational insecurity

The list is endless. All children are unique, and what one has a sensory aversion to probably won’t be the same as the next, but being aware of these struggles and learning how to notice them and address them is paramount.

So let’s approach this in everyday terms and real-life situations.  More often than not, in real life scenarios, other triggers may also be present. For example, while at school, there may be many other factors present that may cause a child to feel upset, confused,  annoyed, etc.  Peer relations can often be a challenge for many kids.  Just regular kid stuff like “she stole my pencil”, “he cut the line” “she keeps looking at me”.  Or, perhaps the content may seem too hard, and the child feels like he/she just doesn’t get it.  The problem is, when you combine these everyday aggravations with SPD, the chances of a meltdown become far greater.

What behaviors will you see in children with SPD?

What behaviors will you see in children with SPD?
What behaviors will you see in children with SPD?

There are two main behaviors that you will see in children with sensory processing vulnerabilities. They are sensory avoiding and sensory seeking.

Sensory Avoiding:  The child will not engage in activities or tasks involving the trigger, for example:  

  • will not touch certain textures
  • will not eat certain foods
  • will not wear certain types of clothing
  • will not engage in certain activities like climbing playground equipment or getting on the swings
  • may cover their ears in response to certain sounds
  • may squint or cover their eyes in certain lighting
  • may avoid brushing hair or teeth
  • may avoid playing in the water

Sensory Seeking:  The child may excessively engage in activities or tasks, for example:

  • bumps into people and things
  • invades the personal space of others
  • fidgets often
  • appears clumsy
  • always moving, can’t sit still
  • plays roughly/extreme risk-taker
  • likes super sour or spicy foods
  • runs their fingers along the wall during school transitions
  • has an extreme tolerance for pain
  • applies extreme pressure when writing
  • always retraces over letters when writing
  • may stare at flickering lights
  • may stare at objects with rotational movement (i.e. blades of a fan)

This is just to name a few.  Really, the list goes on and on because every child is unique resulting in different reactions and behaviors. 

What are the various types of sensory input?

Types of Sensory Input

There are several types of sensory input:  vestibular, visual, proprioceptive, tactile, oral-motor/gustatory,  olfactory, auditory, and interoception.  Here I will provide a brief summary of what each sensory system entails.

Interoception: 

Sensory Processing Explained:  Interoception
Sensory Processing Explained: Interoception

Interoception is not as well known as the other senses we mostly talk about.  It is the awareness of sensations from the organs inside our bodies. For example, how fast our heart is beating, how rapid we our breathing, and whether or not our bladder is full. Interoception also includes the awareness of how our autonomic nervous system is responding to our emotions. For example, if our heart beats faster in response to fear, or if we begin to sweat because we are nervous. Basically, interoception is the ability to feel and understand what is happening inside our bodies.  The organs inside our bodies have receptors that let us know if we are hungry or full, hot or cold, etc.  Children with SPD may have trouble with processing the information the receptors send to the brain.  Children who struggle with interoception may have difficulty with potty training because they may not feel the pressure of a full bladder. They may have an extremely high tolerance for pain. It’s important to be aware that there may be hidden issues when trying to figure out what is going on with your student or child.   

Proprioception (Deep Pressure):

Sensory Processing Explained:  Proprioception
Sensory Processing Explained: Proprioception

Proprioception is our sense of body awareness.  It is the ability of our body to know how it is moving and where it is in space. For example, being able to close your eyes and touch your nose with the tip of your index finger.  Our body knows how to do this because the sensory receptors in our muscles and joints send information to the brain.  This vital information relays how our body is moving, where each body part is in space, and where each body part is in relation to the other.  Try closing your eyes and touching your fingertip to your nose.  Pretty amazing, right?

Children who have a poor sense of body awareness have trouble knowing where their body is or how it is moving in space.  You may notice behaviors like slamming doors, bumping into things, leaning against furniture and walls, and climbing on everything.  They are seeking proprioceptive input or deep pressure.  This type of input provides our bodies with the information needed to modulate.  In other words, proprioceptive input helps to improve body awareness.  It helps children process sensory information and deliver an appropriate response. I’ve covered this topic in great detail in my post about heavy work.  Read more about it here:

What Are Heavy Work Activities And Who Should Do Them?

Vestibular (Movement):

Sensory Processing Explained:  The Vestibular System
Sensory Processing Explained: The Vestibular System

This is any kind of input that causes a change in the movement, position, or direction of the head.  This type of input causes the fluid in the ear canals to move which activates the receptors that are located in the inner ear. The vestibular system largely supports our balance.  When our vestibular system is functioning efficiently we are able to engage and enjoy activities like riding a bike, swinging on a swing, riding in a car or boat, climbing a rock wall, sliding down a slide and many other vestibular activities.  We can enjoy these activities because we naturally feel safe without even thinking about it.  We feel safe because our body and our brain have excellent communication with each other.  This allows us to have a good sense of where our bodies are in space.  When we are threatened by loss of balance, for example, tripping over that toy your little one left in the middle of the floor, your muscles quickly send that information to the brain, and your brain processes that information and tells your muscles what to do in response.  This is called our righting reaction and it happens in a wink of the eye, super fast.  A well-functioning vestibular system is very efficient and keeps us safe.  What happens when our vestibular systems are compromised?  Over-stimulated sensory systems can cause dizziness, car sickness, motion sickness, fear of heights and/or gravitational insecurity, poor balance, and/or frequent falls.  Children may avoid playground equipment like slides, see-saws, and swings, get sick often when riding in the car, appear clumsy or bump into things often.  An under-responsive vestibular system may result in one actively trying to get this type of input (seeking).  Behaviors you may see are rocking in place, spinning in circles, crashing into objects, running into things.  Vestibular input seekers may have difficulty standing or sitting still, so they may wiggle a lot or may demonstrate fidgety behavior.  Children with a compromised vestibular system may not get dizzy after spinning or engaging in rotational movement.

Olfactory (Smell):

Sensory Processing Explained:  The Olfactory System
Sensory Processing Explained: The Olfactory System

Olfactory input is anything that we smell. Our sense of smell is very important and serves many functions.  The receptors in the nose send information to our brain that tells us if what we are smelling is strong or subtle, threatening or pleasant. Our sense of smell also supports taste.  If it smells good, more than likely it is good.  And if we can’t smell food, the flavor just isn’t as intense, much like when we have a stuffy nose.  Emotion and memories are largely connected to our sense of smell via the limbic system.  This is why most of us find the smell of apple pie baking in the kitchen quite comforting.  Whenever I smell a roast cooking in the oven I am immediately taken back to my childhood years when my mom would prepare delicious Sunday dinners.  I can hear the football game playing on the TV as my dad watched, the scent of potatoes and carrots simmering alongside the meat wafted throughout the house.  It is a very fond memory.  Our sense of smell is an integral part of our sensory system.  The olfactory system keeps us safe by helping us understand and process what is happening in our environment. For example, if we smell smoke in the air, our brain will process that information and tell us there may be a fire in our environment. If we smell a gaseous odor, we know we need to take action to protect ourselves.  

Like with other sensory systems, children with sensory processing dysfunction may be over-responsive (hypersensitive) or under-responsive (hyposensitive) to olfactory input.  Children that are hypersensitive may have an adverse reaction to certain scents and/or odors.  They may show signs of irritation to scents that go unnoticed by other people.  For example, the scent of detergent used to clean a child’s clothing may be too harsh, triggering a maladaptive response or misbehavior.  The child’s teacher may not recognize the behavior as a sensory aversion, particularly if she can not detect the smell.  Some responses may be incredibly intense, stimulating the gag reflex causing the child to vomit.  Children who are over-responsive to olfactory input may avoid sensory experiences involving this type of input (sensory avoiding).  They may refuse to eat foods with strong scents and flavors.  They may decline to engage in activities involving scented materials i.e. Strawberry Shortcake dolls, scented slime, or Play-Doh.  They may not be able to tolerate using highly fragrant soaps and/or shampoos, or being near someone wearing perfumes and/or colognes,

Children who are hyposensitive to olfactory input may look for olfactory opportunities (sensory seeking).  You may observe these children smelling peculiar objects like crayons, markers, erasers, really just about anything!   Some scents may trigger a pleasant response, even though it is not safe to smell, like markers and cleaning supplies.  With both hypersensitivity and hyposensitivity to olfactory input, safety may be compromised because the information sent to the brain may not trigger an appropriate response.   

Vision (Sight):

Sensory Processing Explained:  The Visual System
Sensory Processing Explained: The Visual System

Visual input is anything that we capture with our eyes, our sight.   Visual input is the light, color or movement that we see in our environment. As with all types of sensory stimuli, children with SPD may be over-responsive or under-responsive to visual input.  Children who are hypersensitive to visual input may be distracted by busy or cluttered environments. They may overwhelmed by certain types of lights, flickering lights or intense colors. They may not be able to focus on everyday activities like schoolwork because the environment is too visually distracting. They may avoid visual input by covering their eyes, squinting, or avoiding the input all together i.e refuse to enter a room with adverse lighting or colors (sensory avoiding). Children who are hyposensitive to visual input may not notice the details of their environment. They may get lost when presented with information visually. They may seek visual input by staring at objects or moving things (sensory seeking).  

Tactile (Touch):

Sensory Processing Explained:  The Tactile System
Sensory Processing Explained: The Tactile System

Tactile input is anything that we touch or anything that touches us.  The tactile system registers temperature, pressure, tickle, itch, vibration, as well as pain.  Tactile input or touch can be light or firm, wet or dry.  It is the feel of various textures. Through touch, we are able to explore and navigate our environment.  Children may be hypersensitive or hyposensitive to tactile input.  Those who are hypersensitive may avoid tactile experiences (sensory avoiding).  What behaviors will you see?  Children may refuse to engage in any type of messy play or will refuse to get dirty during any activity.  You may see signs of distress like grimacing, crying or even screaming.  Children with tactile vulnerabilities may not wear certain types of clothing or may be irritated by tags on clothing. They may dislike brushing teeth or combing hair. They may avoid activities where their hands get messy like finger painting or carving a pumpkin. They may not touch or will barely touch soap and water when washing hands.  They may not tolerate the application of lotion. Children with tactile defensiveness may avoid foot to floor contact by toe walking.  Children who are hyposensitive to tactile input will seek out this type of input in attempt to regulate themselves.  These kids are constantly touching things.  For example, when walking down the hallway, they are running there hands along the wall.  They may touch everything around them, for example the objects on the table they are sitting at, the furniture in the room, and oftentimes other people/peers.  They may crave hugs, and invade personal space by standing to close to others.  You may see children with tactile hyposenstivity constantly fidgeting with the items in their hands.  

Auditory (Hear):

Sensory Processing Explained:  The Auditory System
Sensory Processing Explained: The Auditory System

Auditory input is sound or anything that we hear.  Our ears receive  auditory information and sends it to the brain.  Our brain tells us how  to respond.  For example, if someone calls our name, our brain processes that information and we respond by turning our head in the direction of the sound and answering the person.  Sounds can make us aware of a dangerous situation, like the ringing of a smoke alarm.  Sounds can impact our mood, like when putting a baby to sleep by playing calming lullabies.  Children with a well-functioning auditory system are able to discern what sound is important and what sound should be filtered out or ignored.  For example, a child is able to tune in to what the teacher is saying and filter out the noise buzzing from the air conditioner’s motor.  They are able to adapt to noisy or loud environments and do what is expected of them.  For example, children with well-functioning auditory systems are able to eat lunch in the noisy cafeteria without signs of aversion.  For children with auditory sensitivities, eating lunch in the cafeteria is an arduous feat.  

Children can be over-responsive to auditory input and some may be under-responsive.  Loud noises like fire trucks speeding down the street, smoke alarms, and construction sites can be overwhelming for those who are over-responsive to this type of input. You may see signs of distress like covering ears, grimacing, or trying to avoid the sound altogether by fleeing the area (sensory avoiding). Children who are under-responsive to auditory input may look for auditory experiences in attempt to regulate themselves (sensory seekers).  Auditory seekers may talk loudly, make humming sounds, and sing to themselves frequently. 

This is not to be confused with auditory processing disorder which is a condition that impacts how the brain processes and understands speech.  Auditory processing disorder makes what people are saying difficult to understand.  A study conducted by the American Academy of Pediatrics has found that symptoms of auditory processing disorder were largely unrelated to auditory sensory processing.

Oral Motor/Gustatory (Taste):

Sensory Processing Explained:  Oral Motor Gustatory
Sensory Processing Explained: Oral Motor/Gustatory

When we think of oral input most of us think of taste and flavor.  But there are actually three different types of sensory input received orally.  Of course, taste is one of them.  We also receive tactile input, anything that touches our oral cavity, meaning our lips, tongue, teeth, inner cheeks, and gums.  The joints that move our mouth, our jaws, also receive sensory input known as proprioception.  Chewing on something hard for example provides a lot of proprioceptive input orally.  Sucking is another way of gaining this type of input.  Again, some children may be over-responsive or under-responsive to oral input.  Those who are under-responsive may present as oral sensory seekers.  You may see these children chewing on their collars, chewing on pencils, chewing on or licking random objects, pocketing food, and constantly putting things in their mouths.  Those that are under-responsive to oral input will present quite differently.  Typically these children will demonstrate sensory avoidance behaviors.  They may dislike brushing their teeth. They may avoid eating foods with various textures and flavors.  Behaviors may be quite challenging during oral hygiene, meals, and snacks.  Children with intense food aversions may have very limited tolerance for varied foods, eating only a few items.  Most often this requires the attention of the child’s pediatrician who may then refer to an occupational therapist that specializes in feeding disorders.

Types of Sensory Input at a Glance:

Types of Sensory Input at a Glance

Fun Strokes Freebie: Types of Sensory Input PDF

If you are a visual learner like me, you’ll enjoy these free PDFs which explain the types of sensory input at a glance!

Fun Strokes Freebie: Types of Sensory Input PDF

How can you help a child with sensory processing disorder? Stay tuned for Part Two of the Sensory Series: “How to Create a Sensory Smart Classroom or Home”. In this post I will offer practical sensory solutions that can be readily implemented in your classroom or home. Free printables and PDFs will be included. You don’t want to miss it!

References

Coulter RA. Understanding the visual symptoms of individuals with autism spectrum disorder (ASD). Optom Vis Dev 2009;40(3):164- 175.

How Scent, Emotion and Memory are Intertwined and Exploited https://news.harvard.edu/gazette/story/2020/02/how-scent-emotion-and-memory-are-intertwined-and-exploited/

Light Sensitivity and Autism, ADHD, SPD, and Developmental Delays https://epidemicanswers.org/light-sensitivity-and-autism-adhd-spd-developmental-delays

Krusemark, E. A., Novak, L. R., Gitelman, D. R., & Li, W. (2013). When the sense of smell meets emotion: anxiety-state-dependent olfactory processing and neural circuitry adaptation. The Journal of neuroscience : the official journal of the Society for Neuroscience, 33(39), 15324–15332. https://doi.org/10.1523/JNEUROSCI.1835-13.2013

Moore, D.R, Ferguson, M.A, Edmondson-Jones, M.A., Ratib, S., & Riley, A. Nature of Auditory Processing Disorder in Children.  Pediatrics published online Jul 26, 2010; DOI: 10.1542/peds.2009-2826

Price, C. J., & Hooven, C. (2018). Interoceptive Awareness Skills for Emotion Regulation: Theory and Approach of Mindful Awareness in Body-Oriented Therapy (MABT). Frontiers in psychology9, 798. https://doi.org/10.3389/fpsyg.2018.00798

Published by Linda Craig Dennis

Pediatric Occupational Therapist, Author and Creator of Fun Strokes Pre-writing Program

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