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Are you able to sense fear?

We sweat in different circumstances. When we exercise (obviously)! But also, when our fight or flight reaction is triggered, for example when we feel fear, one response our body produces automatically is cold sweat.  

But is there really a difference between the two types of sweat? And even if there is, surely we can't easily tell the difference, can we?  

Jumping Off the Plane

Dr Lilianne Mujica-Parodi at Stony Brook University in New York State worked with the US Defence Advanced Research Projects Agency to find out. Dr Mujica-Parodi's team:


  • taped absorbent pads to the armpits of 20 volunteers, who did their first tandem skydive. As these volunteers did their virgin skydive, the absorbent pads collected sweat from these volunteers throughout the jump.

  • the same 20 volunteers were then asked to run on a treadmill with a fresh set of the same type of absorbent pads taped in the same way to their armpits. To ensure fairness, the volunteers for the same period of time as their entire skydive experience, at the same time of the day.

  • The two types of sweat pads were then processed through a nebuliser (that changes liquid to vapour, i.e. sweat to smell).  

  • A new set of volunteers were then asked to breathe in the vapourised sweat. (What! isn't that gross?! Well, 1) Sweat by itself is actually odourless; 2) there's really no other way to do this; and 3) well the participants were not told what they were breathing in).

  • The volunteers breathed in the 2 types of vapourised sweat wearing a brain scanner

  • Their brain scans were then observed.

What were the results?


From the brain scanner:

  1. When the volunteers breathed in the sweat from skydivers, there was significant activation of the amygdala and hypothalamus - the parts of the brain that triggers in association with fear. 

  2. There was minimal activation when volunteers breathed in the sweat from the gym-goers.

From volunteers' verbal description:

  • Volunteers couldn't distinguish the two types of sweat. Actually, they could barely make out any scent at all, they described both types of sweat as mild and non-aversive. 

So what this mean?

Our brains process a lot of information subconsciously, without us even knowing. This is extremely common - the chair you are sitting in, the amount of pupil dilation, body language, small amounts of hormones fed to a particular person, the subliminal messaging in advertisements, the sticker of a pair of eyes at the bus-stop (this list goes on and on*) - things which you are not even aware of can cause you to behave differently, to make different decisions. 

The activation of your amygdala and hypothalamus causes you to become more conservative in your subsequent actions. You become more risk-averse. You're more likely to conform. You are more likely to be harsher to people who disagree or who are different from you in obvious ways.

And all this happens without you knowing that it is happening. Like the volunteers who don't even realise that their amygdalas and hypothalamus have been triggered - they just think they are making their decisions on their own accord. 

Now we make many decisions every day. It's impossible for us to have complete control over every single decision. But for the important decisions, you can come up with a routine to help you minimise errors. 

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