Highly Sensitive Person (HSP)

A person with Sensory Processing Sensitivity (SPS) can also be said to be a Highly Sensitive Person, or HSP. In common media you will see the HSP terminology whereas in more formal research and publications the SPS terminology is more often used. If you want to find research articles on this topic, your best option is to search for Sensory Processing Sensitivity. 

Description of Sensory Processing Sensitivity

A person with Sensory Processing Sensitivity (SPS) takes in more sensory details. They seem to have less "filtering" of sensory data - especially for any new things or environments. They might also notice nuances in meaning and subtle things that others overlook - in what people say, in the environment, or slight shifts in sensory details in a room or in nature.

While it is possible for a person with SPS to have more sensitive perception - such as excellent vision or hearing outside the normal range for humans - this is not what defines them as SPS. It is elsewhere in their brain that results in how the person is responding to stimuli (for a very good example, see the section on Misophonia in the unit, Synesthesia).

Arousal

When a person with sensory processing sensitivity is exposed to stimuli, they might or might not initially feel the results of that stimulation. In other words, they might not have reactivity, at least not right away.

When they do feel a reaction (whether they outwardly display it or not), we can say their sensitivity is aroused. Prolonged or new stimuli can result in heightened arousal.

As Dr. Elaine Aron explains, unconscious arousal over time can become draining of energy even when the person isn't actively aware of the sensory stimuli (6-7). For example, people have discussed becoming increasingly agitated when near large power lines, especially the older ones. It might be surprising - including to the person with SPS - if they suddenly have an emotional or physical reaction to the ongoing stimuli.

While the response might seem sudden, the stimulation and arousal wasn't sudden, and the person didn't suddenly gain SPS (they always have SPS); it was just not noticed until that person's threshold for it was exceeded. Once they reached their breaking point, it might have been too late to remain outwardly calm about it.

Even after eliminating the source of stimulation, or leaving the stimulating environment, a person with SPS can still have ongoing arousal. Sometimes a person can get "sensory echoes" where they continue to "hear" the sounds or feel the sensations for awhile. Retreating to a quiet, usually dimly-lit room can help. It might take hours for the sensations to finally dissipate. 

Examples of Sensitivities

Sensory Processing Sensitivity can present itself in many different ways, and each individual with SPS is unique in their areas of sensitivity and how they respond to them. 

Texture sensitivity can show up in the material preferences in one's clothing, or on things such as furniture. A child with SPS might be more open to hugs, for example, depending on what the other person is wearing. Tags in clothing might need to be removed. Fabrics might need to be softened. 

The noise of lights, plugs, and electrical devices not normally noticed by most people can be a source of arousal and distraction for a person with SPS. School buildings often have loud light fixtures that a student with SPS will find distracting and exhausting. Note: this is a common scenario where the student might not think to mention it (or any other sensory sensitivities) because they might have come to expect that this is just how the world is. They might internalize the idea that it's somehow their fault or burden to bear, and they might not even have any strategies or tools for doing so.

Super tasters might notice every single flavor, and too many at once might make food difficult to eat. New flavors can be their own challenge. Sometimes what tastes or feels bland to many people can have a strong flavor for a person with SPS. Spicy food - even when "mild" - can feel more extreme too.

Similarly, scents can be noticed and processed differently for a person with SPS. A person might notice a scent not easily detected by another person, and that scent might also be overwhelming even though others seem unaffected.

Colors and color combinations can also be stimulating, especially if the color combinations seem discordant or somehow "off" for the individual.

Combine all of this with the condition known as synesthesia - where modes of perception combine or even trigger unrelated senses - and the possibility for sensory arousal can increase.

The above are just a small sampling of examples of how a person with SPS can be impacted by sensory stimulation. A person with SPS might have many other sources of stimulation. Similarly, a person with SPS might not experience arousal with all or any of the above examples.

Walk in the Park and Time Square

The phrase "a walk in the park" is supposed to represent an easy or peaceful thing to do. Somebody with SPS might very much enjoy a walk in the park, but they will likely take in sensory data at a higher level than somebody without SPS. For a person with SPS, a walk in the park might even be similar to a non-SPS person talking a walk through Time Square in New York. 

Now imagine somebody with SPS trying to walk through Time Square. Will it be overwhelming? It could be. Even if it is enjoyable in the moment, it could result in the need to recover from the sensory stimulation later. Meanwhile, if a person is very familiar with Time Square, it might have become less arousing to the senses due to the familiarity. Each individual is unique.  

Sensitivity versus Disorder

Let's quickly note that you might find another term out there, and it looks very similar at first glance: Sensory Processing Disorder (which used to be called Sensory Integration Disfunction).  

It's possible for somebody to have both sensory processing sensitivity and sensory processing disorder (SPD). It can also be difficult to distinguish between the two in some people because some of the possible traits look similar. However, there are also distinct differences.

SPD is described by the Star Institute as "the way the nervous system receives messages from the senses and turns them into appropriate motor and behavioral responses. Whether you are biting into a sandwich, riding a bicycle, or reading a book, your successful completion of the activity requires accurate processing of sensation." What if you couldn't initially feel the sensation of biting into a sandwich? Or you were unable to sense messages from muscles and joints; how well could you ride a bike? 

With SPD, a person might be over-responsive or under-responsive to stimuli. A person who is under-responsive might even try to seek out more or stronger sensory stimulation.

Sensory Processing Sensitivity, however, is only about higher sensitivity and over-responsiveness. The key difference, as noted by Dr. Jadzia Jagiellowicz of the Highly Sensitive Society: "brain research indicates that individuals high in sensory-processing sensitivity are better able to integrate sensory information than less-sensitive individuals, which is not the case for children with SPD."

If you want to learn more about Sensory Processing Disorder, view the Star Institute's "About SPD" page for information and a list of symptoms. 

Learn More About Sensory Processing Sensitivity

The Highly Sensitive Person: Resources offers information and resources for people who have SPS, and for parents of children with SPS.

References Cited

Aron, Elaine N. The Highly Sensitive Person: How to Thrive When the World Overwhelms You. Harmony Books, 2016.

Other references are directly linked.