Your brain does not wait until it receives stimuli from the outside world to produce its image of the world. It anticipates what will happen in the next moment and presents this to you as current reality. Based on your experiences in life up to now, this happens with enormous reliability. To save energy, stimuli from the outside are only taken into account when they don't sufficiently match your current model of the world. In these cases, prediction errors cause your brain to reconsider its model of the world.

By constantly adapting its model of the world, your brain limits the number of prediction errors, and thereby its energy consumption, to a minimum. In addition, it discards anything it considers to be interference or normal variation in a given situation in order to reduce the number of stimuli to be taken into account.

If you wish to learn more about this topic, please read my previous article on the predictive brain. Now let's talk about hypersensitivity.

Hypersensitivity

Around 2005, I came across the first books that talked about hypersensitivity, and I recognized myself in them. It refers to an extraordinary sensitivity at the sensory and emotional levels. At the time, I didn't know that I was autistic and that hypersensitivity was even a criterion for diagnosing autism. After recognizing myself on the autism spectrum in 2022, I began to meet other autistic people and realized that the majority of them are extremely sensitive, often much more so than I am, which sometimes causes them serious problems in their daily lives. It is a major reason for their recurring fatigue and even exhaustion.

Hypersensitivity in people with autism

Hypersensitivity can affect all the senses. Here are some examples of what may be disturbing to a person with autism:

• auditory: certain sounds, even faint ones, background noise
• visual: bright light, lots of moving objects in the field of vision
• tactile: touch, however slight and accidental
• olfactory: perfume, smoke
• gustatory: foods with a certain texture or specific taste

Keep in mind that sensitivities vary a lot from one autistic person to another. One person might feel a touch as intense pain, while the same touch might be really nice for someone else. In addition, some people are hyposensitive in certain areas, meaning they have a very weak reaction to stimuli. For example, one person may not realize they are burning themselves because they do not feel pain.

Hypersensitivity can manifest emotionally as well. Many autistic people experience intense emotions when another person is suffering or when there is tension between people. This could explain their strong sense of justice, which makes them uncomfortable when they witness injustice and abuse.

Hypersensitivity is not limited to autistic people, but affects around 20% of the population. It is overrepresented in people with ADHD and those with high intelligence.

The role of stimulus intensity

We imagine that the louder a noise is, the more disturbing it is. This is often the case, but not always. When we discussed our sensitivity to noise among autistic people in a support group, we found that this was not the case. One person who was normally very sensitive to noise could use a drill without it bothering them too much. They said that the loud noise of the drill could be anticipated and controlled. In my case, the noise of children playing doesn't bother me much. On the other hand, a barely audible sound in a room at the photography museum in Winterthur disturbed me greatly.

Although sound volume plays a role, it is not the only factor. Even neurotypical people are affected. A colleague explained to me that after soundproofing the exterior walls, tenants complained about noise from their neighbors, which had not bothered them before.

Not at the level of the senses

In fact, the term “sensitivity” is not entirely accurate to describe this phenomenon. Researchers have discovered that it is not the sensory signals reaching the brain that differ between autistic and non-autistic individuals, but rather how the brain processes them. There is therefore no difference in the nervous system that captures sensory stimuli. It would be more accurate to talk about “hyperreactivity” because the brain gives too much importance to certain sensory signals and reacts too intensely.

According to the predictive brain theory, the role of your senses is simply to verify your brain's predictions to ensure that its model of the world does not stray too far from reality. Your brain therefore does not wait for sensory signals, but predicts them and then considers only the difference between the prediction and the feedback from the senses, focusing solely on prediction errors.

During their research, scientists observed that the autistic brain tends to take prediction errors more seriously. In non-autistic people, also called neurotypicals, small random variations or disruptive elements in the data captured by their senses are dismissed. In contrast, the autistic brain immediately considers them important, which forces it to adapt its existing model.

This can be interpreted such that autistic brains produce absolute and highly precise models of the world, making generalizations difficult. The result is a particularly narrow and rigid perception. Consequently, any situation that does not quite match previous situations may be considered unique. As a result, these brains tend to trust less their existing models of the world. They therefore place greater importance on external signals, i.e. prediction errors. They cannot ignore them, even if they are irrelevant to the situation at hand, such as slight background noise. The sound of dripping water in the background may prevent some people with autism from hearing what someone is saying.

As far as I'm concerned, I find that after noticing an insignificant detail, such as a clothing label sticking out of someone's clothes, I have trouble letting it go and focusing on something else. Such an insignificant detail can distract me for quite some time. Although I am aware of this, I can't do anything about it.

Surprises everywhere, all the time

While neurotypical people quickly get used to new stimuli and stop paying attention to them, autistic brains continue to treat them as new and important much longer. This is why some autistic people remain very aware of buzzing lights and rumbling AC units. Studies confirm that they take longer to get used to repeated stimuli. Some autistic people even need several weeks to get used to a new piece of clothing. You can imagine how annoying that can be.

I would like to share a personal example. At the beginning of a course, I noticed that the bottom button of the instructor's shirt was undone. It bothered me and distracted me the entire time. There was nothing I could do about it. During the first break, I approached the trainer and asked him to button it up, which he did. For the rest of the day, I didn't pay any more attention to his shirt and was able to concentrate fully on the content of the course.

The reduced level of prediction may explain hypersensitivity in autistic people, as their brains pay increased attention to insignificant stimuli in their environment. Because of this, it is not surprising that autistic people tend to be surprised by many things that go unnoticed by others who may not even realize them.

This vigilance does have a positive side when it comes to paying attention to details and detecting errors. Many autistic people are very skilled at tasks that require this ability.

Distinctive features of autistic perception

Scientific studies show that the brains of everyone, whether autistic or not, respond less and less to frequently repeated stimuli. However, autistic brains respond more intensely when a deviant stimulus is presented with some regularity. On the other hand, if there is no regularity, the reaction is weaker compared to neurotypical individuals. These observations are interpreted in such a way that autistic brains take less account of context, i.e. the regularity of a deviant stimulus.

Autistic perception is characterized by the following features:

• Too much importance is given to exceptions and coincidences (or too little in the case of hyposensitivity, which is also common among autistic people)
• Surprises caused by insignificant variations, making it difficult to generalize
• Overestimation of the random and capricious nature of the real world and underestimation of its hidden regularities
• Less attention paid to context, which would provide additional clues to understanding a situation and reducing prediction errors
• Attachment to the literal meaning of a word or expression and difficulty perceiving the figurative significance
• Less flexibility in interpreting a situation

All these effects can be explained by the predictive brain theory. These characteristics are generalizations, and it is important to bear in mind that there is enormous diversity among autistic individuals.

Benefits of autistic hypersensitivity

People with autism easily perceive the disadvantages of their hypersensitivity:

• Severe disruption, even physical pain, caused by stimuli that others can easily handle (or do not even perceive)
• Recurring fatigue and exhaustion due to sensory overload

However, it should be kept in mind that the hypersensitivity of autistic people does have positive aspects. The way their brains work makes certain types of activities easier for them. Studies show that people with autism perform well in tasks that require sustained attention to detail, such as spotting a particular detail in an image or identifying musical pitches. They also tend to be less susceptible to visual and multisensory illusions, which rely strongly on certain expectations within the perceptual system.

In our noisy and ever-changing world, it seems essential to be able to quickly distinguish between what is important and what is superfluous. Under such conditions, the functioning of the autistic brain may appear to be a disability. However, it does have its advantages.

• Very logical, consistent, and reasoned thinking, which is necessary in sectors where strict and unchanging rules must be followed.
• Attention to detail, which allows them to spot errors that others do not notice.
• Ability to pay attention to details despite routine and monotony.
• Fewer stereotypes, as autistic people view more situations as unique and are therefore less influenced by prejudice.
• Strong sense of justice because they are very sensitive to unreliability and injustice.

These characteristics represent a key skill in professions that require a high level of precision and reliability.

The more restricted worldview of autistic people does not necessarily mean less creativity. Many common patterns are underlying and, for this reason, are not picked up by their brains. By not paying attention to them, they may be able to come up with highly creative and innovative solutions.

Strategies for managing hypersensitivity

Being more aware of prediction errors means that you can focus and maintain your attention on details that others overlook. In certain contexts, this characteristic is a real advantage for autistic people.

But in everyday life, the low level of prediction is often cumbersome, as the autistic brain pays too much attention to mundane and insignificant signals. This causes sensory overload, which autistic people frequently suffer from. Managing all these errors is energy-intensive, leading to fatigue and even total exhaustion. The next article in the series on the predictive brain will present strategies for managing hypersensitivity as effectively as possible.

Keep in mind: huge differences between autistic people

I'm repeating myself, but I want to stress this really important point. Always remember that perceptions and needs vary a lot from one autistic person to another. What's totally fine for one person might be unbearable and cause a strong reaction in another.

Main source:

• VERMEULEN, Peter, 2022. Autism and the predictive brain: absolute thinking in a relative world. Abingdon, Oxon ; New York, NY : Routledge. ISBN 978-1-03-237491-8.
  
  

This article was first published in French in November 2024 and has now been translated into English by the author himself.

Author of the article: Beát Edelmann, expert in neurodiversity (autism, ADHD and high IQ) and personality exploration. He is the founder of the Abundana Institute for Self-Management in Geneva, which offers coaching, training, and consulting services in French, English, and German.

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