Sensory Sensitivity and Autism

Hyper- or hypo reactivity to sensory input or unusual interest in sensory aspects of the environment is a core diagnostic criterion for autism (APA, 2022). Sensory sensitivity is one of the earliest signs of autism and can be recognised in infancy. The sensitivity can be across all sensory modalities, life-long and affect the ability to engage in social and community activities, thus increasing loneliness and reducing quality of life (Quadt et al., 2023). Sensory sensitivity will also affect attention and concentration and contribute to anxiety, depression and meltdowns. Sensory sensitivity is not unique to autism and is recognised as a characteristic of other neurodevelopmental disorders such as ADHD and schizophrenia.

Nearly 90% of autistic children experience sensory sensitivity (Gandhi et al., 2021) and over 90% of autistic adults (Crane et al., 2009). The sensitivity does not habituate with repeated exposure, and the criticism ‘Just get used to it’ does not recognise that the experience can be extremely painful and is not easily diminished by distraction and mental effort.

There can be hyper-reactivity to external sensory experiences such as sounds, light intensity and touch (Exteroception) and hypo-reactivity to some external experiences and sensing the body’s internal states such as heart rate, breathing and hunger (Interoception). Some sensory experiences can be perceived as extremely enjoyable.

Auditory sensitivity

Acute auditory sensitivity can occur in response to specific sounds (hyperacusis), particularly sudden or ‘sharp’ noises, a specific pitch, or aspects of speech. The ‘sharp’ noises can include the sound of a dog barking, someone shouting, coughing or clapping, fireworks, loud vehicles and construction tools. Pitch sensitivity can be to small electric motors such as hand dryers and vacuum cleaners, the sound of the fan inside a computer, and someone singing off the key. There can also be a sensitivity to competing voices and sounds, such as multiple conversations or several radios playing in an office.

Temple Grandin describes her auditory sensitivity:

“Sudden loud noises hurt my ears like a dentist’s drill hitting a nerve. High pitched continuous noises such as hair dryers and other small motors are annoying. All the behaviour modification in the world is not going to stop an autistic child from screaming when a noise hurts his ears.”

Loud, sudden noises still startle me. My reaction to them is more intense than other people’s. I still hate balloons, because I never know when one will pop and make me jump. Sustained high-pitched motor noises, such as hair dryers and bathroom vent fans, still bother me, lower frequency motor noises do not.

The auditory sensitivity can be to many everyday sounds that are difficult to avoid, and the anticipation of these aversive experiences will increase anxiety and reduce the motivation to engage in social and family events and community activities. Auditory sensitivity will also affect the ability to fall asleep with a startled reaction to nighttime sounds. However, auditory sensitivity could lead to a greater appreciation of music, learning to play an instrument, a career in the music industry and sound engineering and social connection in being a member of a band, orchestra or choir.

Tactile sensitivity

There can be acute sensitivity to specific tactile experiences, even light touch on particular parts of the body, for example, hair washing or hair or nail cutting, the sensation of rough textures, perceiving the seams and labels of clothing, food texture, unexpected touch from someone, and tight clothing. There can be tactile hyposensitivity, such that some tactile experiences are not noticed.

Tactile sensitivity will affect the experience of some expressions of affection, such as a kiss or hug. 

Temple Grandin describes her tactile sensitivity:

“I pulled away when people tried to hug me, because being touched sent an overwhelming tidal wave of stimulation through my body.”

“Church was a nightmare because the petticoats and other Sunday clothes itched and scratched. Many behaviour problems in church could have been avoided by a few simple clothing modifications.”

“As a baby I resisted being touched and when I became a little older I can remember stiffening, flinching, and pulling away from relatives when they hugged me”.

“As a child I wanted to feel the comfort of being held, but then I would shrink away for fear of losing control and being engulfed when people hugged me”

The sensitivity to touch could also affect aspects of sexual intimacy (Gray et al., 2021)

Tactile sensitivity can also affect the perception of surfaces, such as the fabric used for chairs and having to sit on a carpet at school, but can be associated with an enjoyable experience, such as feeling cold metal surfaces and soothing clothing, as in the comment It’s just a scarf, but it could be quite comforting to wear, I stroke the material (Kyriacou et al., 2023).

Visual sensitivity

Visual sensitivity can be due to light type, intensity, colours, and patterns. Bright and flashing lights can be aversive; fluorescent lights are perceived as flickering, bright sunlight is ‘blinding’, and some forms of lighting can trigger a headache or migraine. Supermarkets can be a source of aversive visual experiences, such as bright shop lighting, multi-colour packaging, and shiny floors. Some colours or colour combinations can be distressing, as described by an autistic teenager:

“I also remember one Christmas, when I got a new bike for a present. It was yellow. I would not look at it. Extra red was added to the colour making it look orange, and it blurred upwards making it look like it was on fire”

Some patterns can create visual distress, such as the vibrant pattern on a carpet, which is perceived as an optical illusion and “painful for my eyes”.

Visual sensitivity can lead to abilities such as drawing with attention to detail, being aware of lighting as a photographer, and noticing symmetry and patterns as an architect.

Olfactory sensitivity

The sensitivity can be to specific olfactory experiences such as perfumes and deodorants, the smell of specific food, and cleaning chemicals, as described in the following comment: “They had a new hand gel in the toilet, and I just couldn’t use it as it was so overpowering. Olfactory sensitivity can also affect the perception and acceptance of someone: “They could be the nicest person in the world, but if I don’t like how they smell, they were evil to me.

Olfactory and tactile sensitivity can combine to affect the perception of food, especially food with a fibrous texture, multiple flavours and a distinct aroma. There can also be a fear of swallowing, choking and trying new foods that contribute to Avoidant/Restrictive Food Intake Disorder (ARFID). Sean Barron described that in his childhood,

“I was supersensitive to the texture of food and I had to touch everything with my fingers to see how it felt before I could put it in my mouth. I really hated it when food had things mixed with it….I could never put any of it into my mouth. I knew if I did I would get violently sick”.

There can be a tendency to eat different foods consecutively, and some foods create excruciating pain: “Eating a pear to me felt like sharp pins being put into my throat”

Parents can be concerned that nutritional needs are not met with avoidance and anxiety due to the sensory characteristics of food. This may be one of the contributory factors to developing an eating disorder such as anorexia nervosa (Brede et al., 2020).

Interoception

Interoception is the sense of the body’s internal states, such as pain, illness, heart rate, breathing, muscle tension, hunger, satiation, thirst and the need to go to the toilet. There seems to be a mind/body division described in the comment: 

“Autism is being locked inside yourself, but it’s being disconnected from yourself too”. 

An autistic person may forget to eat or drink for long periods of time and have limited cognitive awareness of pain, injury, exhaustion and sleepiness. An example is the comment, “I had no idea I was sick and going to vomit until about 3 seconds before”, and “I’m insensitive to my body’s signals that I need to go… I’m very often extremely desperate to go once I finally realise…”

A difficulty perceiving increased heart rate, breathing and muscle tension will affect the ability to perceive increasing anxiety, agitation, imminent meltdown and the ability to regulate emotions. Problems with interoception will also affect the accuracy of medical examinations. The best way I can describe this to health professionals is that I receive a signal from somewhere I’m not exactly sure, and I have difficulties interpreting what they might mean

There can also be hypersensitivity to internal sensory experiences, such as “I’m super sensitive to any little changes in how my body feels and I always worry that I might have some serious deadly terminal scary disease”. This can lead to the autistic person being perceived as having hypochondria and experiencing anxiety associated with the internal sensations associated with digestion.

Screening and measuring instruments for sensory sensitivity

Winnie Dunn is the author of the Sensory Profile 2 (2014), which assesses children’s sensory profiles. Catana Brown and Winnie Dunn have published the Adolescent/Adult Sensory Profile (2002). Olga Bogdashina has published the second edition of her book Sensory Perceptual Issues and Autism (2016), which includes a 140-item checklist based on the sensory profile associated with autism. We also have the Sensory Perception Quotient (SPQ) (Tavassoli et al., 2014), an instrument that measures the visual, hearing, touch, smell and taste perception of autistic adults. These are examples of the SPQ items:

• I can recognize different people by the way they smell
• I can hear electricity humming in the walls
• I can’t go out in bright sunlight without sunglasses
• I would be the first to hear if there was a fly in the room
• I can see dust particles in the air in most environments
• I would be able to hear the sound of a vacuum cleaner from any room in a two-storey building
• I would be able to hear each note in a chord even if there were ten notes
• I would be able to smell the smallest amount of burning from anywhere in the house

The Glasgow Sensory Questionnaire (Robertson and Simmons (2013) has items that measure
hyper and hypo-sensory sensitivity, such as:

• Do you notice that you have hurt yourself but did not feel any pain?
• Do you react very strongly when you hear an unexpected noise?

The Interoception Sensory Questionnaire (ISQ8; Suzman et al., 2021) has eight items that explore difficulties in perceiving internal body sensations. Examples of the questions are:

• I have difficulty making sense of my body’s signals unless they are very strong
• There are times when I am only aware of changes in my body because of the reactions of other people
• I find it difficult to identify some of the signals that my body is telling me (e.g. If I’m about to faint or I’ve overexerted myself)

The screening and measuring instruments for sensory perception are not just research tools but practical aids that can be used to explore an autistic person’s sensory perception. By understanding their experience of specific sensory experiences, these tools can indicate what environmental accommodations are needed at home, school, work, and in a consulting or therapy room. This practical application empowers educators, therapists, parents, and individuals to make informed decisions and create supportive environments.

Synaesthesia

Synaesthesia is experiencing a sensation in one sensory modality that activates a sensation in another modality. The most common expression of synaesthesia is a written word, symbol, or sound that triggers the perception of a colour. For example, the letter ‘A’ evokes the colour red. Musical notes can also elicit colours, or a word elicits a specific taste, such as the word ‘parents’, creating the sensation of the taste of an apple. Synaesthesia is rare in non-autistic adults, occurring in 2-4% of the adult population, but around one in five autistic adults have synaesthesia (Baron-Cohen et al., 2013).

We have known autistic adults who have described their perception of a coloured ‘aura’ around people with the colour indicative of personality characteristics which can be used to identify people to avoid or accept.

It is important to recognise that synaesthesia is an aspect of the sensory profile associated with autism and a sign of sensory, not mental, disturbance. Some synesthetes have used this characteristic in the creative arts.

Emotional sensitivity

Our clinical experience and autobiographies confirm that autistic individuals are extremely sensitive to another person’s negative emotions, such as disappointment, anxiety or agitation. There seems to be a ‘sixth sense’ ability to perceive ‘negative vibes’; for example, an autistic person may refuse to go into a room of people, not necessarily due to auditory or visual sensitivity, but saying they ‘just feel negativity in the room’. We have found that this emotional sensitivity is often an accurate perception of the emotional ‘atmosphere’.

Emotional sensitivity may be one of the reasons why autistic individuals avoid crowds due to the risk of proximity to someone who is experiencing a negative mood and being ‘infected’ by that mood. Emotional sensitivity may also contribute to a characteristic of autism of avoiding eye contact as the eyes convey feelings (Smith, 2009).

Emotional sensitivity can occur with all expressions of autism. Robert Hughes (2003) wrote about his non-speaking autistic son, Walker, whom he described as being a “supersensitive emotional barometer who registered the true emotional pressure in the air, no matter how hard we tried to mask it”.

In his autobiography, Aaron Wahl (2019) wrote…. I perceived the feelings of others often overly clearly but could not find access to my own, which may be due to aspects of interoception associated with autism as described in part 1 of Sensory Perception and Autism.

Other autistic adults have described:

I am able to distinguish very subtle cues that others would not see, or it might be a feeling I pick up from them.

There’s a kind of instant subconscious reaction to the emotional states of other people that I have understood better in myself over the years.

Negative emotions in others can be ‘infectious’ to an autistic person. One of our clients said Emotions are contagious for me. If someone approaches me for a conversation and they are full of worry, fear or anger, I find myself suddenly in the same state of emotion.

As clinicians, we help an autistic person create a mental barrier, such as using the metaphor of imagining a forcefield, putting on a suit of armor, using a shield for protection or putting up an umbrella to keep ‘dry’ from a downpour of emotions. We also encourage autistic people to explain their sensitivity to someone’s negative mood and that the reason for their temporary withdrawal or avoidance of them is a coping mechanism due to emotional sensitivity and not a rejection of them as a person.

Dr Stephen Porges (2017) coined the term neuroception to refer to the primitive neurocircuitry we all have as human beings that help us to detect threat and danger. Neuroception is pre-conscious, so at first, we may not even be aware that our bodies are getting ready for fight, flight or freeze.

 Autistic people are more susceptible to both experiencing trauma, including trauma from daily exposure to feeling different/defective and experiencing exclusion, and developing post-traumatic psychological symptoms, for example, hypervigilance, distrust of others, nightmares etc. Autistic emotional sensitivity describes contagion of negative affective states from other people, such as stress and anger, rather than positive affective states such as joy and excitement. It is possible that, due to different wiring, extremely high levels of anxiety and/or trauma, an autistic person has highly attuned or very sensitive neuroception, which explains their high levels of sensitivity to other people’s emotions.

Sensory pleasure

Some sensory experiences can be extremely pleasurable, calming or fascinating for an autistic person (Smith & Sharp, 2013). These sensory pleasures are one of the positive aspects of autism. There can be a fascination with order and symmetry, such as train tracks and the ‘sleepers’ between the tracks, picket fences, streetlights and telegraph poles, creating a sense of well-being due to the consistency and predictability. Visual acuity can lead to a fascination with the perception of details, for example, in the structure of a feather, being mesmerised by watching the spinning drum of a front-loading washing machine or appreciating the various tones of yellow in a garment or painting. Heightened auditory perception can lead to appreciating complex music, which can also positively affect mood. Olfactory and oral sensitivity can make some foods extremely enjoyable, such as appreciating the quality of handmade Belgian chocolate or French champagne.

Unfortunately, enjoyment can lead to being ‘stuck in the moment,’ as described by a participant in the Smith and Sharp study: “I don’t know how long I was there, but I remember the car behind me beeping and people shouting at me as I watched the traffic lights change over and over… I was intrigued.”

Strategies for accommodating sensory sensitivity

Sensory integration therapy (SIT) was originally developed by occupational therapist A. Jean Ayers in the 1970s to help children with sensory-processing difficulties. The sensory-based interventions provide sensory activities or experiences to help children improve internal sensory processing and self-regulation and develop adaptive functioning skills. The programme has successfully been used with autistic children and is recognised as an evidence-based practice (Schoen et al., 2018).

Autistic children and adults also benefit from strategies discovered by parents or autistic people themselves. Auditory sensitivity can be reduced by wearing ear plugs, noise-attenuating or industrial headphones, or background music. Some sounds can be avoided, such as vacuuming when an autistic child is at school.

Sensitivity to the type and intensity of illumination can be reduced by wearing sunglasses when outdoors, a baseball cap, hat, or visor for bright downlights, or replacing fluorescent with incandescent lighting.

The sensory world can be frightening for an autistic child, and some autistic children have discovered that being mesmerised by a repetitive action or sensation can be a coping or escape mechanism. Temple Grandin explained that when she was a child:

“Intensely preoccupied with the movement of the spinning coin or lid, I saw nothing or heard nothing. People around me were transparent and no sound intruded on my fixation. It was as if I was deaf. Even a sudden loud noise didn’t startle me from my world. But when I was in the world of people, I was extremely sensitive to noise”

‘Stimming’ may have beneficial effects in reducing sensory sensitivity, which has recently been confirmed by research on repetitive behaviour. (Charlton et al., 2021; Nwaordu and Charlton, 2023)

In our conversations with autistic adults Autistic who have sensory sensitivity, they have explained that the sensory experience is less distressing if they can control the initiation and intensity of the experience. The experience is not a surprise, and they have the means of ending the sensory experience.

Finally, we know that sensory sensitivity and anxiety co-regulate each other. Increasing anxiety increases sensory sensitivity and vice versa. Programmes to reduce anxiety will increase the tolerance of sensory sensitivity, and a reduction in sensory sensitivity will reduce anxiety.

References

APA (2022) Diagnostic and Statistical Manual of Mental Disorders-5 Text Revision. American Psychiatric Association
Baron-Cohen et al. (2013) Autism 4
Bogdashina, O (2016). Sensory Perceptual Issues in Autism and Asperger Syndrome. London, Jessica Kingsley Publishers
Brede et al, (2020) Journal of Autism and Developmental Disorders 50
Brown, C & Dunn W. (2002). The Adolescent/Adult Sensory Profile Pearson Assessments
Charlton et al. (2021). Research in ASD 89 101864
Crane et al., (2009) Autism 13
Dunn W. (2014). Sensory Profile 2 Pearson Assessments
Gandhi et al., (2021) Journal of Autism and Developmental Disorders 51
Gray et al. (2021) Autism in Adulthood
Hughes R (2003). Running with Walker Jessica Kingsley Publishers
Kyriacou et al., (2023) Journal of Autism and Developmental Disorders 53
Nwaordu and Charlton (2023) Journal of Autism and Developmental Disabilities 53
Quadt et al. (2023) Autism in Adulthood
Robertson and Simmons (2013) Journal of Autism and Developmental Disorders 43
Schoen et al (2018) Autism Research 12
Smith, A. (2009) The Psychological Record 59 489-510
Smith and Sharp (2013) Journal of Autism and Developmental Disorders 43
Suzman et al. (2021) Molecular Autism 12:42
Tavassoli et al. (2014) Molecular Autism 5:29
Wahl A. (2019) Ein tor zu eurer welt KNAUR