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Can People Really Smell Fear?

Fictional characters, and even real-life folks, often talk about animals and people—particularly snarling dogs and knife-wielding lunatics—being able to “smell fear” on people. No one ever seems to be able to describe just what fear smells like, though.

The lack of detail—Is it musty? Does it have a hint of vanilla?—leads one to think that the smell of fear is more metaphorical than literal. But scientific evidence suggests that fear might really have a chemical component that we sense through our noses without even realizing it. The matter is far from settled, though.

Right Under Your Nose

In 2009, a team of German researchers collected sweat from two groups of students, one where the sweat came from exercising on bikes and one where it came from the stress of waiting to give a graded oral presentation.

A third group of students, lying in fMRI scanners and wearing modified oxygen masks, then smelled air odorized by the two groups’ sweat. Asked about what they were smelling, the students didn’t even notice an odor in half of the trials. When they did notice they were smelling something, they were unable to tell the difference between the two sources and rated both as low in intensity, weakly pleasant, unfamiliar, and having no effect on their own emotions.

The brain scans told a very different story, though. After smelling the sweat of the students nervously waiting for their exams, the smellers’ brains showed increased activity in areas that are involved with empathy and processing social signals and the emotional states of other people. The sweat from exercise didn’t cause these same activations, suggesting that the nervous students’ sweat contained some sort of chemical signal of their anxiety that triggered a response in the smellers’ brains without registering as the sensory experience of a smell.

That same year, a pair of psychologists at Rice University collected sweat from different volunteers while they watched horror movies or slapstick comedies, and then asked other volunteers to smell the sweat while they looked at images of faces that switched expressions from happy to ambiguous to fearful. As the faces morphed, the volunteers were asked to indicate whether they thought the expressions were happy or fearful.

The smellers were more likely to judge the ambiguous faces as fearful after being exposed to the the horror watchers’ sweat than when they smelled the comedy watchers’ sweat or a control sweat. That behavioral change suggests that not only did the sweat contain some chemical signal that communicated emotion, but also affected people’s visual perception of emotions and biased them towards the one being communicated by the sweat (that second part is consistent with other findings that emotional cues from faces and voices can regulate each other).

Just last month, Dutch psychologists found evidence that fear-induced sweat not only biases someone who smells it toward seeing fear, but might also push them to feel it themselves. Volunteers either watched scenes from a scary movie or from Jackass, and their sweat was collected. People in another group were then exposed to the smell of one of the sweats while they took a visual test that asked them to find a target object on screens full of different items. While this was going on, the researchers recorded their facial expressions and tracked their eye movements.

The people who got the horror sweat made facial expressions suggesting fear or anxiety shortly after they were exposed to the sweat. The Jackass-sweat smellers, meanwhile, made disgusted faces. (This was determined by comparing their faces to “distinctive facial-muscle signatures” associated with emotions. For more on face reading, check out Paul Ekman and his facial action coding system.) The two sweats also appeared to have affected the smellers’ behavior, with the horror sweat smellers attempting to acquire more sensory information while exposed to the sweat by taking bigger sniffs and scanning more and fixing their gaze less during the visual exercise.

What the Nose Knows

What all this, and a bunch of other studies looking at the same sort of thing, suggests is that humans might not communicate by just sight, sound, and touch. Like other animals, we might also use chemical signals embedded in our sweat, and maybe elsewhere, to let each other know about our emotional states.

That has been a contentious idea for a very long time, with some people claiming “definitive evidence of human pheromones,” and others saying “no, not so fast.” While there’s a good amount of evidence for behavioral and physiological changes in people in response to “chemosignals,” no one has been able to nail down just what the chemicals are that trigger these responses, and how people detect them. The vomeronasal organ, which many animals use to detect pheromones, is present in some humans, but doesn’t appear functional. When scientists can find them in people, the genes that code for their receptors don’t seem to have done their job, and their sensory neurons have little or no connection with the central nervous system.

Those are two very important dots that need to be connected before the line between someone’s sweaty armpit and someone else’s schnoz can be drawn clearly.

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Big Questions
How Are Balloons Chosen for the Macy's Thanksgiving Day Parade?
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The balloons for this year's Macy’s Thanksgiving Day Parade range from the classics like Charlie Brown to more modern characters who have debuted in the past few years, including The Elf On The Shelf. New to the parade this year are Olaf from Disney's Frozen and Chase from Paw Patrol. does the retail giant choose which characters will appear in the lineup?

Balloon characters are chosen in different ways. For example, in 2011, Macy’s requested B. Boy after parade organizers saw the Tim Burton retrospective at the Museum of Modern Art. (The company had been adding a series of art balloons to the parade lineup since 2005, which it called the Blue Sky Gallery.) When it comes to commercial balloons, though, it appears to be all about the Benjamins.

First-time balloons cost at least $190,000—this covers admission into the parade and the cost of balloon construction. After the initial year, companies can expect to pay Macy’s about $90,000 to get a character into the parade lineup. If you consider that the balloons are out for only an hour or so, that’s about $1500 a minute.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
Why Do the Lions and Cowboys Always Play on Thanksgiving?
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Rey Del Rio/Getty Images

Because it's tradition! But how did this tradition begin?

Every year since 1934, the Detroit Lions have taken the field for a Thanksgiving game, no matter how bad their record has been. It all goes back to when the Lions were still a fairly young franchise. The team started in 1929 in Portsmouth, Ohio, as the Spartans. Portsmouth, while surely a lovely town, wasn't quite big enough to support a pro team in the young NFL. Detroit radio station owner George A. Richards bought the Spartans and moved the team to Detroit in 1934.

Although Richards's new squad was a solid team, they were playing second fiddle in Detroit to the Hank Greenberg-led Tigers, who had gone 101-53 to win the 1934 American League Pennant. In the early weeks of the 1934 season, the biggest crowd the Lions could draw for a game was a relatively paltry 15,000. Desperate for a marketing trick to get Detroit excited about its fledgling football franchise, Richards hit on the idea of playing a game on Thanksgiving. Since Richards's WJR was one of the bigger radio stations in the country, he had considerable clout with his network and convinced NBC to broadcast a Thanksgiving game on 94 stations nationwide.

The move worked brilliantly. The undefeated Chicago Bears rolled into town as defending NFL champions, and since the Lions had only one loss, the winner of the first Thanksgiving game would take the NFL's Western Division. The Lions not only sold out their 26,000-seat stadium, they also had to turn fans away at the gate. Even though the juggernaut Bears won that game, the tradition took hold, and the Lions have been playing on Thanksgiving ever since.

This year, the Lions host the Minnesota Vikings.

HOW 'BOUT THEM COWBOYS?


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The Cowboys, too, jumped on the opportunity to play on Thanksgiving as an extra little bump for their popularity. When the chance to take the field on Thanksgiving arose in 1966, it might not have been a huge benefit for the Cowboys. Sure, the Lions had filled their stadium for their Thanksgiving games, but that was no assurance that Texans would warm to holiday football so quickly.

Cowboys general manager Tex Schramm, though, was something of a marketing genius; among his other achievements was the creation of the Dallas Cowboys Cheerleaders.

Schramm saw the Thanksgiving Day game as a great way to get the team some national publicity even as it struggled under young head coach Tom Landry. Schramm signed the Cowboys up for the game even though the NFL was worried that the fans might just not show up—the league guaranteed the team a certain gate revenue in case nobody bought tickets. But the fans showed up in droves, and the team broke its attendance record as 80,259 crammed into the Cotton Bowl. The Cowboys beat the Cleveland Browns 26-14 that day, and a second Thanksgiving pigskin tradition caught hold. Since 1966, the Cowboys have missed having Thanksgiving games only twice.

Dallas will take on the Los Angeles Chargers on Thursday.

WHAT'S WITH THE NIGHT GAME?


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In 2006, because 6-plus hours of holiday football was not sufficient, the NFL added a third game to the Thanksgiving lineup. This game is not assigned to a specific franchise—this year, the Washington Redskins will welcome the New York Giants.

Re-running this 2008 article a few days before the games is our Thanksgiving tradition.

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