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Fear is so wired in us we can literally smell it

It's a terrible cliche used in some of these terrible Hollywood movies. There's a villain hunting down his victims, and he declares:

"I can smell your fear".  

Wow ok. Cringe.

The only thing is... it's somewhat true. You can actually smell fear. 

In this study, Dr Lilianne Mujica-Parodi et al:

  1. Taped absorbent pads to the armpits of 20 first-time skydivers ­– 11 men and nine women. These pads were placed to soak up the sweat of these new sky-divers before they leapt from the plane and as they fell.  

  2. The team then taped the same type of absorbent pads on the same individuals, to soak up the sweat as they ran on a treadmill for a similar duration at the same time of day they had made their jump.


So one type of sweat, from skydiving, was emotional, namely fear and anxiety.

The second type of sweat, from running, was simply from physical exertion. 

The team transferred the two types of sweat to nebulisers and asked volunteers in a brain scanner to breathe it in. The volunteers were, of course, not told about what they were breathing in and whom it came from. 


And what were the results? 

When volunteers "smelled" the sweat of pure physical exertion, there was no obvious effect in ther brains except for those related to olfaction (or smell).


But when volunteers "smelled" the sweat from fear of skydiving, the brain scanner records activities in the amygdala and hypothalamus. You should know by now that the amygdala is the part of the brain responsible for fear, anger, anxiety, and aggression. And the hypothalamus is the brain centre that gives the command for hormones to be produced, in response to the fear that was sensed. 

It's crucial to also point out that the volunteers could not consciously distinguish between the 2 types of sweat. They rated both types of sweat as mild and not offensive. 

But amazingly, although we can't tell the difference, our brains can. It is able to tell, just from a little bit of sweat, whether someone was fearful or not! And in turn, this sparked our own fear centre, the amygdala, which also triggers the release of more hormones. We become slightly more anxious, edgier, and defensive. 

And this goes to show just how much of our brain works without us knowing.  There are many factors unknown to us, that affects what sort of thoughts we come up with and what reactions we have. But because we can only be aware of what we are aware of, we think it is because of our own conscious processing that we develop that thought or had that reaction. And we then come up with a story to explain why or what we did. 

Check out:  


Image by Filipe Dos Santos Mendes


Sweat collected from first-time skydivers who experience a range of emotions before and during jumping 

On the Treadmill


Sweat collected from the same people who go through a purely physical experience of running on a treadmill

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