What is SPD? Sensory Processing Disorder, formerly Sensory Integration Disorder

sensory processing disorder definition SPD

Our nervous system is constantly organizing sensory input in the form of sights, smells, touches, and sounds. When functioning properly, our brains are subconsciously able to sort this information and prioritize it based on urgency. 

If we’re hungry, the smell of pizza will pull our attention more strongly than the smell of a scented candle. If a loud firetruck goes by, the sound of the sirens will draw our attention more than the music we’re playing. 

Throughout all of the smells and noises, we’re subconsciously able to balance our bodies under our feet, stand upright, walk around, and feel relatively calm. Our bodies are able to switch from one source of sensory input to another without getting overloaded or overwhelmed.

This is what life WITHOUT Sensory Processing Disorder is like.

Now, let’s look at what life WITH Sensory Processing Disorder is like.

Sensory Processing Disorder (SPD) is described as the nervous system’s inability to properly organize and prioritize the sensory input we receive from the world around us.

An individual with SPD can get easily overwhelmed, as their brain is trying to attend to a lot of sensory input all at once. The noises, smells, touches, and sensations all take top priority. When a firetruck’s siren goes by, it gets added on top of the music playing, and the brain tries to pay attention to both noises at once. Add a scratchy shirt tag, a smelly restaurant, and a desperate need to go to the bathroom and you have a brain that is massively overloaded and on the verge of meltdown.

It’s impossible to paint Sensory Processing Disorder with a broad brush, as it appears in a unique way in every person. Firstly, people differ in the types of sensory input they react negatively to. For example, some people are more sensitive to tactile input—they may be comfortable with loud sirens, but a scratchy shirt tag will cause a meltdown. Secondly, people differ in their sensitivity to various sensory inputs. For example, some people are ok with low levels of sensory input, but not high levels—they may be comfortable watching a movie at home, but the loud volumes and crowded aisles at a movie theater are overwhelming.


To put it simply—we all react to sensory input differently. Noises, sounds, touches, and sensations all create different responses in our brains. When this reaction begins to impede on everyday functioning, we typically call it Sensory Processing Disorder.

Let’s dive a little deeper into Sensory Processing Disorder’s 3 sub-categories.

Sensory Modulation Disorder (SMD)

Sensory Modulation Disorder (SMD) is the tendency to either over respond or under respond to sensory input. As a result, the cause doesn’t always match the effect. For example, a soft noise may trigger a large startle response or a large noise may not be acknowledged at all. Within SMD, an individual may be over responsive, under responsive, or sensory seeking.

Over Responsivity

Someone who is over responsive to sensory input is often sensitive to sights, smells, sounds, and touches. The hum of a fan may sound as grating as a jack hammer; the smell of a floral perfume may be nauseating; the sight of an action movie may cause anxiety. As indicated in the name, someone who is over responsive tends to respond to sensory input in a magnitude greater than is normally expected.

Under Responsivity

Juxtaposed to over responsivity, under responsivity indicates that someone isn’t strongly impacted by the sights, smells, sounds, and touches around them. Often manifesting itself as apathy, those who are under responsive often seem disinterested in sensory experiences. The smell of chocolate chip cookies isn’t tantalizing; the sound of a favorite song doesn’t catch their attention; a high-paced action movie isn’t exciting. As indicated in the name, someone who is under responsive tends to respond to sensory input in a magnitude lesser than is normally expected.

Sensory Seeking

Unlike the first two categorizations, sensory seeking behavior has to do with one’s craving for specific sensory experiences. Chewing on a pen is calming; spinning really fast on a tire swing feels good; listening to a certain type of music at a loud volume is energizing. As indicated in the name, someone who is sensory seeking tends to crave specific activities that satisfy one’s sensory desires.

Sensory seekers are often mistaken for having ADHD. While it’s true that sensory seekers can often have ADHD, these two conditions aren’t synonymous and can exist independently.

This fact is why it’s important to take careful notice of behaviors prior to making diagnostic determinations and to check with a doctor or therapist before moving forward with any specific treatment or plan of action.

Sensory Based Motor Disorder (SBMD)

Our proprioceptive and vestibular systems tell us where our bodies are in space. They help us stand up tall, keep our balance as we move, and coordinate complicated 

movements such as writing, speaking, and walking. When these systems are out of whack, we have a hard time taking in sensory input so as to move about in our environments.

Someone with SBMD would struggle when navigating physical environments. They may easily fall when standing and walking, may take longer to regain balance after being pushed, and may have challenges with fine motor skills such as buttoning up buttons. In crowded environments, a person with SBMD may become frustrated by their inability to move around with ease.

Sensory Discrimination Disorder (SDD)

If you’ve ever played a game where you try to identify the tastes of different foods with your eyes closed, you have an idea of what SDD feels like. Someone with SDD struggles to identify and differentiate between sensory stimuli. A red Skittle tastes like a green one; the sound of a siren blends in with the sound of a friend talking; sand feels the same as rice. With SDD, it can be hard to navigate the world, as sensory input is hard to categorize and make sense of. While someone with SDD recognizes sensory experiences, they are harder to categorize and process.

Sensory Processing Disorder Come in Many Forms

As you can see, SPD manifests itself in many ways. It can look very different from person to person and from context to context. In addition, SPD functions on a spectrum, with some people expressing symptoms more so than others. While some may find a noise slightly annoying, others may be unbearably overwhelmed by that same noise. This is what makes SPD so interesting, but also so confusing and complicated.

As with any condition, it’s important to realize that SPD is a label that helps us identify behaviors so that we can better address them.

People are not confined to labels though. The label of SPD is only as helpful as it is helpful to the person experiencing it. No matter the characteristic symptoms of SPD, everyone is different and needs to be appreciated beyond the diagnostic labels. In essence, don’t take these SPD descriptions as law. While they can be guides to understanding your child’s behavior, only your child can give you the entire road map.

Treatment for Sensory Processing Disorder

When thinking about treatment, it’s important to consider the challenges that your child specifically has. As you can see from the description above, SPD comes in many shapes and sizes. One child with SPD is one child with SPD.

Treatment for SPD normally happens in Occupational Therapy sessions. Following a thorough evaluation, your child’s Occupational Therapist will be able to determine your child’s unique challenges and develop a specialized treatment plan to address them.

Regardless of its numerous manifestations, treatment for SPD usually revolves around improving the body’s skills at sensory integration (ie. taking multiple sensory experiences and processing them efficiently instead of getting overwhelmed by them). Sensory integration activities can include anything from swinging, climbing, and jumping to shaving cream finger painting, texture play, and auditory games.

Treating Sensory Processing Disorder at Home

If your child has SPD, don’t try to tackle it alone. Always work closely with an Occupational Therapist to find the best solutions for your child. But, if you’re already working with an OT and you want some ideas for diving deeper into sensory integration at home, here are some suggestions.

Note that all of the suggestions and links below will apply to your child. As SPD covers a wide range of areas, so do the activities surrounding them. Pick and choose activities and products that would be appropriate given your own child’s needs.

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