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ASPartOfMe
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28 Nov 2017, 12:43 am

Odors that carry social cues seem to affect volunteers on the autism spectrum differently

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. As reported in Nature Neuroscience, Weizmann Institute of Science researchers show that people on the autism spectrum have different -- and even opposite -- reactions to odors produced by the human body

To conduct their experiments, Sobel and lab members Yaara Endevelt-Shapira and Ofer Perl, together with other members of his lab, devised a series of experiments with a group of participants on the high functioning end of the autism spectrum who volunteered for the study. To begin with, the researchers tested the ability of both autistic and control volunteers to identify smells that can be consciously detected, including human smells like sweat. There was no significant difference between the groups at this stage, meaning the sense of smell in the autistic participants was not significantly different from that of controls.

Two groups were then exposed to either to the "smell of fear" or to a control odor. The smell of fear was sweat collected from people taking skydiving classes, and control odor was sweat from the same people, only this time it had been collected when they were just exercising -- without feeling fear.

This is where differences emerged: Although neither group reported detecting dissimilarities between the two smells, their bodies reacted to each in a different way. In the control group, smelling the fear-induced sweat produced measurable increases in the fear response, for example in skin conductivity, while the everyday sweat did not. In the autistic men, fear-induced sweat lowered their fear responses, while the odor of "calm sweat" did the opposite: It raised their measurable anxiety levels.

Next, the group created talking robotic mannequins that emitted different odors through their nostrils. These mannequins gave the volunteers, who were unaware of the olfactory aspect of the experiment, different tasks to conduct. Using mannequins enabled the researchers to have complete control over the social cues -- odor-based or other -- that the subjects received. The tasks were designed to evaluate the level of trust that the volunteers placed in the mannequins -- and here, too, the behavior of autistic volunteers was the opposite of the control group: They displayed more trust in the mannequin that emitted the fear-induced odor and less in the one that smelled "calmer."

In continuing experiments, the researchers asked whether other subliminal "social odors" have a different impact in autism than in control groups. In one, the volunteers were exposed to sudden loud noises during their sessions while at the same time they were also exposed to a potentially calming component of body-odor named hexadecanal. Another automatic fear response -- blinking -- was recorded using electrodes above the muscles of the eye. Indeed, the blink response in the control group was weaker when they were exposed to hexadecanal, while for those in the autistic group this response was stronger with hexadecanal.

In other words, the autistic volunteers in the experiment did not display an inability to read the olfactory social cues in smell, but rather they misread them.

Next, the group created talking robotic mannequins that emitted different odors through their nostrils. These mannequins gave the volunteers, who were unaware of the olfactory aspect of the experiment, different tasks to conduct. Using mannequins enabled the researchers to have complete control over the social cues -- odor-based or other -- that the subjects received. The tasks were designed to evaluate the level of trust that the volunteers placed in the mannequins -- and here, too, the behavior of autistic volunteers was the opposite of the control group: They displayed more trust in the mannequin that emitted the fear-induced odor and less in the one that smelled "calmer."

In continuing experiments, the researchers asked whether other subliminal "social odors" have a different impact in autism than in control groups. In one, the volunteers were exposed to sudden loud noises during their sessions while at the same time they were also exposed to a potentially calming component of body-odor named hexadecanal. Another automatic fear response -- blinking -- was recorded using electrodes above the muscles of the eye. Indeed, the blink response in the control group was weaker when they were exposed to hexadecanal, while for those in the autistic group this response was stronger with hexadecanal.


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Amaltheia
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28 Nov 2017, 1:32 am

Interesting.

I only have one quibble:

Nature Neuroscience wrote:
In other words, the autistic volunteers in the experiment did not display an inability to read the olfactory social cues in smell, but rather they misread them.

Since the autistic subjects were clearly not confusing the two odors — that is, they weren't misidentifying one for the other, or failing to distinguish between them — and they had consistent responses to each odor, I don't think it's valid to say they "misread" them. They apparently read them just fine; they just respond to them differently.

This sentence suggests an underlying assumption that the correct response to detecting fear in others is to feel fear oneself. Now, that may be a valid position, but the author should establish that clearly and explain why they believe that's the case, rather than just assume it.



Last edited by Amaltheia on 28 Nov 2017, 1:52 am, edited 1 time in total.

Amaltheia
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28 Nov 2017, 1:48 am

It occurs to me that feeling fear when identifying that those around you are afraid would be a valid response for herd animals. That way, if one animal detected danger, triggering a fear response, the rest of the herd would detect the fear, if not the danger, and would respond. This would clearly increase the survival chances of all the animals in the herd.

On the other hand, solitary animals would only detect fear in others when either hunting, the fear of the prey would be an expected response, or when accidentally stumbling across some other animal. In both cases, responding to the fear by becoming calm and remaining collected would allow the solitary animal to deal with the situation more effectively — either killing the prey, or backing out of the unexpected encounter without a fight.

So, in a way, this finding provides some support for Jared Reser's Solitary Forager Hypothesis of Autism.



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28 Nov 2017, 2:38 am

I do not know how well this study was done but it does dovetail with the sensory criteria.


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traven
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28 Nov 2017, 3:01 am

Yea, the human is not only a herd-animal (on a social scale) but also a preditor (on the food scale), as preditor it's hugely inconvenient to move around in herds, except for hunting within the herd.

The huge imagery of herds moving around, followed by their preditors, you miss the human link in it, they're filming, driving, flying, doing all sort of things, but not taken into count(view) is them being still there as (slightly transformed) preditors following the other preditors, as it would be slighly stupid to go in front of the lions :mrgreen:


one for diversity, a lower or slower response can be deadly, as it can be livesaving



Amaltheia
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28 Nov 2017, 3:23 am

traven wrote:
Yea, the human is not only a herd-animal (on a social scale) but also a preditor (on the food scale), as preditor it's hugely inconvenient to move around in herds, except for hunting within the herd.

I don't think human beings are herd animals. They're more troop-style animals: they organise themselves into bands or troops, with each troop tending to define a territory which they defend against other troops, with the members of the troop dispersing to hunt or forage individually or in small groups. Herd animals like to stay together, get deeply distressed if separated from the herd, and forage as a unit.

I was pointing out that a contagious fear response would be a useful trait for herd animals. For troop animals, a mixture of contagious fear and non-fear responses within the group would be optimal, since that would allow for heightened arousal of the group, but would help avoid — or at least diminish — stampeding through panic.

I don't know how autism fits into this, but it may be that autistics are just the extreme end in a spectrum of susceptibility to contagious fear. After all, all those leaders who kept their heads while all around them were losing theirs probably weren't autistic, but they clearly were less susceptible to contagious fear than their fellows.