I SMELL YOUR FEAR: No, Seriously, It's Science

Turns out all that tough talk about being able to smell fear might actually have some validity, according to some researchers in The Netherlands who just published a study on chemosignals.
Publish date:
November 8, 2012
science, smell

Turns out all that tough talk about being able to smell fear might actually have some validity, according to some researchers in The Netherlands who just published a study on chemosignals. In “Chemosignals Communicate Human Emotions,” appearing in Psychological Science, they examined two distinctive human emotions, fear and disgust, and decided to determine whether it was possible to smell them, via chemosignals, in a double-blind study.

Now, “smell” is a bit of a misleading word. It’s not so much smell in the sense of “stop and smell the roses,” but, as the name suggests, a chemical signal that can be used to express communication between individuals. Lots of animal species take advantage of chemosignals; people who work with animals may have noticed, for example, that animals can pick up on their emotions and may turn that to their advantage. Or, you know, cuddle you when you're having a bad day, depending on the species and your relationship.

Woah, careful where you're going with that probe!

In this study, the researchers assembled a cavalcade of dudes and put them on smell contamination protocol for several days. The men weren’t allowed to eat strong-smelling food, smoke, use scented personal care products, or handle anything that might have a strong odor. Then, they watched movies designed to evoke either a disgust or fear response, and then, speaking of disgusting, the researchers collected sweat samples from the study participants.

Next, women participants were asked to perform “a visual search task” while they were exposed to the scent. The researchers observed them closely while they worked for signs of fear or disgust responses. Frightened people tend to widen their eyes, flare their noses, and scan their area visually. These hallmark signs of fear aren’t just a way to communicate that you’re afraid; they also happen to make it more likely that you’ll survive a threat, because you’re more alert to your surroundings. CONSTANT VIGILANCE, as Mad-Eye Moody would say.

Disgusted people, meanwhile, demonstrate what’s known as “sensory rejection.” You know the look. Wrinkled nose and half-closed eyes, attempting to avoid whatever it is that’s completely grossing you out, like, say, stale dudesweat collected by a bunch of folks in white coats.

It also serves a purpose, and not just an aesthetic one. If you're not huffing something that smells bad, you're less likely to inhale enough of it to get sick, if it something that's bad for you. And your disgusted chemosignals might be a useful and discreet tip for the people around you. Dude, seriously, don't try any of Aunt Mabel's cranberry sauce, there's something wrong with it.

Being able to transmit information through chemosignals would actually be pretty great, turning each individual human into a little canary in the coal mine. If there’s something in the air that’s dangerous to breathe, for instance, the disgust chemosignal could warn other people in the area. Likewise, sending fear signals would have been useful back in our earlier days when we were a bit lower on the food chain and being able to communicate wordlessly about a Big Bad approaching could have saved lives.

I love the smell of dudesweat in the morning

What the researchers found was that, lo and behold, the women exhibited responses in line with the chemosignals they were exposed to. Women smelling fear sweat widened their eyes, increased visual scanning, and, uh, demonstrated an increased “sniff magnitude.” Those exposed to the disgust sweat showed signs of sensory rejection. This confirms earlier findings indicating that people can smell emotions, and that emotions are associated with specific chemosignals.

Researchers have already noted that individuals who are emotionally close can smell emotions like love, and chemical signals play a key role in communication. The hormone oxytocin, for example, works doubletime when it comes to bonding. It's involved in breastfeeding, childbirth, and, oh yeah, sexytimes. And, of course, pheromone products of varying believability have been marketed for years as an adjunct to the perfume industry.

The sense of smell, along with the accompanying sensitivity to chemosignals, is one of the oldest senses, and the things the nose can do are pretty cool. Even though humans aren’t nearly as sensitive as some other animals, like dogs, apparently our noses are sharper than previously believed, and we do indeed have the capability to sniff our way to understanding, as it were.

A little whiff of gender bias?

You might be interested in knowing why the study used men to produce sweat and called upon women to smell it. One reason was for greater control over the study conditions, to ensure that the researchers were getting the most useful results. Sexual dimorphism among humans is an established and inescapable fact, although sexual variations beyond male and female are more common than people might assume, with approximately 1% of the population exhibiting intersex characteristics. While the profile of the study population didn't mention whether transgender and transsexual participants had been evaluated and excluded, I would think could potentially be a confounding factor as well.

When you're doing science, you want the most controlled environment possible.

The reasoning behind using male donors and female receivers was also purely practical; women appear to have a better sense of smell than men. Furthermore, the researchers stated, men tend to produce stronger signals. I’d be interested to see the same study replicated with all-female groups, all-male groups, men smelling women’s sweat, and intersex participants as well as transgender ones to learn more about how scent serves as a vehicle of communication, and what role sex and gender may or may not play in that.