A fear response to smelling calm chemicals

Studies have found that when people are afraid, they release chemicals that are picked up by others, and act as a contagion, making others afraid. Autistic people, however, have a different response.

Smelling emotions

While most of us are aware that autistic people have a challenge with interpreting facial expressions, what fascinated me was that we have the same challenge with the odours that we are unaware of smelling, but which are, nonetheless, a part of the nonverbal communication that perplex us.

Humans emit odours that allow them to determine smells that announce such emotions as happiness, fear or aggression, and this in turn affects our own moods and behaviour. For example, a non-autistic person who unconsciously smells fear will have an increase in their own heart rate.

Smelling fear

In 2017, researchers tested a group of autistics and non-autistics to see if both groups of participants could detect odours—which they could.

Then both groups were exposed to sweat from people who were skydiving (experiencing fear), as well as sweat from the same people who were exercising without experiencing fear.

When the group of non-autistic participants smelled the fear-induced sweat, they reacted by producing a fear-like reaction in their own body, while the odour of the calm sweat did not raise their level of anxiety.

But the autistic people reacted in exactly the opposite way; when smelling fear, they became calmer, and when smelling calm sweat it raised their levels of anxiety.^[1]Autism and the smell of fear; Odors that carry social cues seem to affect volunteers on the autism spectrum differently | Science Daily^[2]Altered responses to social chemosignals in autism spectrum disorder (Shapira et al., 2017)

Trusting fear

In addition, scientists had both groups speak to robotic mannequins that emitted different odours through their nostrils that gave the volunteers tasks to complete. Autistics showed greater trust in the mannequin that released the fear-induced odour and less in the one that smelled “calmer”. This was opposite of non-autistic people who trusted the fear-emitting mannequins less.

Fearing calm chemicals

An additional experiment was conducted where a calming chemical in sweat called hexadecanal was released into a room while a loud unexpected sound occurred. The people without autism were calmed and showed less blinking (blinking is an automatic fear response) when hexadecanal was released, while people with autism became more afraid as indicated by their increase in blink response.

Hyper- and hyposensitivity

A meta-analysis from 2017 which looked at 11 studies on autism and odour detection and identification indicated a wide variety of results, with both a lack of sense of smell (hyposensitivity) and a superior sense of smell (hypersensitivity).^[3]A Meta-Analysis of Odor Thresholds and Odor Identification in Autism Spectrum Disorders But the research did find some interesting correlations when it comes to the results of the various studies. Namely, the researchers found that generally among autistic people:

• Those with IQs above 113 are hypersensitive to odour detection.
• Those with IQs below 113 are hyposensitive to odour detection.
• Those at an age below 30 show hyposensitivity to odour detection.
• Those at an age above 30 show hypersensitivity to odour detection.

As calming pheromones induces a fear response in autistic people, no wonder we do not like social gatherings!