The Sense Cycle 2 - Smelling Fear, Being Disgusting and Hormonal Ups and Downs

By Richard Craven

Another week, another set of articles! Thought I'd include a little personal anecdote in the second article which you might be able to relate to. Enjoy :) 


1. Dentists can smell fear on a patient

The study showed that practicing dentists doing work on mannequins performed much worse on 'fear sweat', than performing on those with little or no sweat. The mannequins wore T-shirts donated by students who took a stressful exam and those who had a calm lecture. The determining factor was not the describable scent (the odour was masked) but an unconscious awareness of something else that made the difference.


Researchers suggest that a "smell of anxiety" could trigger the same emotion in those who are exposed to it. When the T-shirts were presented to a different group of 24 dental students in a non-performance environment,  they were unable to detect any difference between the T-shirts taken from the stressful or the relaxed situations. Further research on the conditions required for identifying stress indicators, blind tests and individuals' stress tolerance levels would link in well with this experiment.

This experiment’s significance is highlighted by Pamela Dalton at Monell Chemical Senses Center in Philadelphia: "Its quite fascinating... It helps us understand how we can communicate without language."

Link to the full paper here:


2. A follow up article to last week's report on disgust - discussion.

Quick recap synopsis: Disgust has evolved as a response to offensive substances that may cause harm to the sensing organism (Parasite Avoidance Theory). We recently posted about a report distinguishing between the types of disgust, and how they are explicitly rated in terms of extreme disgust to no disgust. The report found that the sight of lesions, for example, came out as the most disgusting.

The gist: 'A problem for humans is that our hardwiring for disease transmission cues may not always match real threats.  Shaking hands with a person missing a thumb and viewing an obese individual sunbathing present no danger.’

The criticism: I am inclined to disagree on an evolutionary level, but our humanity is shown in the fact that social/cultural practice and education allow us to overcome any hard wiring derived from our ancestral past. An evolutionary perspective gives us a start for almost any explanation.

A deformed or injured animal is often left abandoned by herds to die because it is considered unfit for to survival and possibly costly to invest in for other herd members - the same explanation can be applied  to human's innate & animalistic instincts as this manifests itself as disgust, but it is a combination of awareness and education that allows us to overcome ancient hardwired instincts. 

From a personal perspective, I once had a wonderfully kind headmaster who, due to an accident, had slightly deformed hands. On required occasions, my peers and I would begrudgingly shake his hand, and almost always end the interaction with bouts of disgusted giggles after he was out of earshot. 

From an evolutionary standpoint, the reason for disgust  was obvious. Why we laughed after the event was perhaps due to uncomfortableness as we didn't have a choice in the matter (courtesy of the social and cultural pressure) and theit wasn't as bad as our hardwired minds implied. In the final balance this proved more powerful, and, encouragingly, with repetition it ceased to be an issue.

Put simply we are not necessarily always hard wired to think or behave in certain ways but we are almost certainly 'pre-wired'. This means we can overcome those instincts through changes in societal norms and cultural sensitivities.

Another example - obesity. On to the topic of the obese individual mentioned, the inherent disgust may be caused as a result of evolutionary biology, in this case because obesity might be a symptom of someone being ‘swollen up because of a disease, like filariasis’. Filariasis is a parasitic disease caused by an infection with certain roundworms. In reality nowadays, few people are overweight because of infectious illnesses, yet the past association may somehow be part of our genetic programming. From an evolutionary perspective, one might be predisposed to having an aversion to obese people.

How does modern culture regard obesity? Remember the uproar of the Beach Body Ready ad?


Fat shaming is very much a modern day issue - interestingly, in recent Western history being fat was a sign of wealth and prosperity because they could eat to their hearts’ content, hence the creation of the Fat Man’s Club.  

It is then a question of why someone might feel potentially put off, for example, seeing a seemingly innocuous obese person on a beach.

Is it because of evolutionary biology?

Is it because society - think adverts, catwalk models etc - appears to favour thin over fat people? This, in itself, might have evolutionary roots.

The simple answer is yes - societal norms and evolutionary perspective appear aligned. 

Once again, however, greater awareness, education and tolerance mean that human are often able to overcome historical or evolutionary instincts. Evolutionary biology is very contentious because it’s not deemed politically correct by those who want to believe everyone is born with a ‘blank slate.’

Link to the article here:


3. Progesterone probably doesn’t increase disgust sensitivity


Mixed bag of evidence whether progesterone increases women’s disgust sensitivity. Logic (and some research) argues that 'This progesterone-linked disgust sensitivity is thought to occur because progesterone suppresses women’s immune system. This reduced immune function might trigger behavioral responses, such as increased disgust sensitivity, to compensate.’ (progesterone levels skyrocket during first 10 weeks of pregnancy, until the placenta is fully formed). However, this may just be a bit of confirmation bias looking to explain the science of it as Benedict Jones and his team at University of Glasgow essentially prove that evidence previously supporting this is ambiguous at best or wrong at worst.

They did find however that 'that women (not necessarily pregnant) demonstrated strong aversions to even subtle facial cues of illness, there was no evidence that the strength of these aversions was regulated by progesterone.

Oh and then Jones and co also suggested the possibility that some specific types of illness-avoidance behaviours that were not considered in these studies may be linked to progesterone (or other hormone) levels in some women, but the conclusions are unclear.


Link to the full paper here:


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