What Is Sensory Processing Disorder (SPD)?

Affecting up to 16% of kids, Sensory Processing Disorder is the most common disorder you’ve never heard of. The Savvy Psychologist explains what is SPD and why it's so misunderstood. Plus, answers to 3 big questions about the disorder.

Ellen Hendriksen, PhD
6-minute read
Episode #59

Imagine pumping up the volume on everything you see, hear, and feel.

A walk on a sandy beach feels like a forced march over broken glass. The sound of a blender makes you feel like you’re inside the engine of a 747. And all you can do is scream until it stops.

But at the same time, imagine turning the volume down so low that other sensory input can barely be perceived. You don’t even feel a tap on your shoulder, but you can register slamming into a wall, or a person. (There’s just the pesky fact that people get mad when you slam into them).

What’s more, when your brain constantly says “What just happened?” to whatever’s coming in, it can take a long time to settle down, get used to something, and focus. Therefore, transitioning to another activity once your brain is finally in a rhythm is maddening. For example, you just got the hang of this indoor lighting thing and now someone says you have to go outside in the sun. It’s totally overwhelming.

What Is Sensory Processing Disorder (SPD)?

Welcome to the neurological puzzle of Sensory Processing Disorder (SPD). Within each of us, a neurological process organizes the sensations that come into our bodies and allows us to respond in kind. But in kids and adults with SPD, that process is impaired.

And this, as Anchorman Ron Burgundy would say, is kind of a big deal.  

Because what in our world can’t we see, hear, smell, taste, or feel? What isn’t presented as sensory information? Indeed, how we respond to something with our bodies, emotions, behaviors, or attention all depends on what sensory information comes in.  

And in kids, all this makes everyday kid stuff difficult. Imagine how overpowering the feeling of hugging or those t-shirt tags or seams on socks might be? Getting a haircut or a fingernail trim might seem like torture and playing with play dough or finger paint might be avoided at all costs.

In general, symptoms of SPD fall into two broad categories: under-responsive and over-responsive. A great explanation I’ve heard is to imagine your processing ability is like a cup. You want your cup to be full, but not to overflow.

With any given sense, if you’re under-responsive, you have a really big cup. Each “drop” of sensory input doesn’t make much of an impact, so you have to keep filling and filling.  

What Are the Symptoms of SPD?

For example, in a typically wired brain, if I pat you on the hand, your nervous system will let your brain know that I’ve touched you lightly. However, if your sense of touch is under-responsive, my touch might not even register. I’d need to pat you much more firmly for your nervous system to notice.

On the flip side, if you’re over-responsive, you have a really tiny cup. Every “drop” of sensory input might overwhelm your cup and your cup overflows really easily. Using the pat on the hand example, my gentle pat might be neurologically interpreted as a sharp hit.

To make matters even more complicated, any given individual might have a different sized cup for each sense.

Your child, for example, may have a tiny cup for sound, and therefore may cover his ears and freak out when the vacuum turns on. At the same time, he may have a big cup for touch and therefore seem impervious to pain (unless it's something like a broken arm).

Most kids with SPD are a mixture of both over- and under-responsive and sometimes a sensation that was avoided like the plague one day is actively sought out the next. The hallmark of the disorder is inconsistency.

To top it off, something called sensory modulation is also a challenge. This is the nervous system’s ability to prioritize some sensory input, like looking at and listening to the teacher, and downplay others, like the noise from the ceiling vent and that distracting fluorescent lighting.

These challenges, of course, are frustrating for folks with SPD, but they're especially rough on parents and caregivers who don't have a magic x-ray into the brain of their child. All they see is the kid screaming bloody murder over a string on their banana and then are perplexed by the same child’s endless need to roughhouse, spin, or swing.

In short, it's a challenging disorder, compounded by the fact that it often gets labeled as something else (like autism or ADHD).


All content here is for informational purposes only. This content does not replace the professional judgment of your own mental health provider. Please consult a licensed mental health professional for all individual questions and issues.

About the Author

Ellen Hendriksen, PhD

Dr. Ellen Hendriksen was the host of the Savvy Psychologist podcast from 2014 to 2019. She is a clinical psychologist at Boston University's Center for Anxiety and Related Disorders (CARD). She earned her Ph.D. at UCLA and completed her training at Harvard Medical School. Her scientifically-based, zero-judgment approach is regularly featured in Psychology Today, Scientific American, The Huffington Post, and many other media outlets. Her debut book, HOW TO BE YOURSELF: Quiet Your Inner Critic and Rise Above Social Anxiety, was published in March 2018.