Skip to main content

We’re just starting to understand how smell can change human behavior. Unsplash

Scientists observed how people reacted to frustrating computer games in the presence and absence of the molecule, known as hexadecanal. Female players took more retaliatory action against their opponents while sniffing the chemical, while men showed the reverse pattern. The team also noted differences between how brain activity changed in men and women during exposure.

The experiments indicate that chemical signals we aren’t consciously aware of may influence our behavior in certain contexts. However, the findings come with several caveats—and more evidence is needed to verify the extent to which hexadecanal actually influences us.

“This definitely needs to be replicated before it can be really fully accepted and generalized,” says Ashok Panigrahy, a professor of radiology, developmental biology, bioengineering, and bioinformatics at the University of Pittsburgh, who was not involved in the research. However, he says, “this study highlights the importance of smell, and how it relates to behavior.”

For most mammals, aggressive behavior is very sensitive to the effects of chemical signals. But little is known about how these processes work in humans, says Eva Mishor, a neuroscientist at the Weizmann Institute of Science in Rehovot, Israel and coauthor of the new findings.

Previously, scientists have reported that hexadecanal reduces stress in mice, while other research has shown that humans release the compound in our feces, skin, and breath, and that it might affect our startle response.

To investigate whether hexadecanal might play a role in human aggression, Mishor and her colleagues ran several experiments in which volunteers played computer games with a mysterious partner. Unbeknownst to the players, this “partner” was actually a computer algorithm designed to provoke them.

In the first experiment, 67 men and 60 women were treated unfairly in a game that involved divvying up a small sum of money. The participants later had the opportunity to blast their uncooperative partner with a loud burst of noise, the volume of which they controlled. During the games, each participant wore a sticky pad pasted to their upper lip, half of which contained hexadecanal.

“We saw there was a small yet highly consistent difference between the groups,” Mishor says.

Women exposed to hexadecanal indulged in more severe noise blasts than women who weren’t exposed, she says, while men who were exposed to the chemical opted for less intense noise blasts than those who weren’t.

The researchers then explored whether the same individual might behave differently while sniffing hexadecanal than in its absence. This time, 25 men and 24 women endured a different aggravating game in which their computer opponent occasionally stole money from them; in turn, the players could also dock money from their partner without gaining it themselves. The researchers tracked how often the participants chose to do this and took fMRI scans of their brains. The team found that on average, women reacted more aggressively when hexadecanal was wafted through the scanner, and men less so.

In both groups, a part of the brain called the left angular gyrus (which is involved in perceiving social cues) became activated during exposure to the chemical. However, a difference between the sexes emerged when the researchers examined how this region “talked” to other parts of the brain.

When men were exposed to hexadecanal, activity in the left angular gyrus became more synced with that in several other brain areas involved in processing social information and aggression: the temporal pole, amygdala, and orbitofrontal cortex. But in women, connectivity between the left angular gyrus and these other regions decreased during hexadecanal exposure.

The findings indicate that these areas “form some kind of a social and emotional-decision making network,” Mishor says. The findings could shed light on different brain mechanisms underlying aggressive behavior in men and women, she adds.

Mishor and her colleagues offer one explanation for the differences in how women and men responded to hexadecanal. “Perhaps the one setting in which it could be highly beneficial to reduce male aggression and increase female aggression is the setting of infant-rearing,” she says.

In other species, Mishor and her team wrote, mother animals often direct their aggression at intruders while fathers and especially other males often behave aggressively toward the infants. Hexadecanal could give babies a tool to increase their odds of survival, they speculate.

As a first step to investigating this idea, the researchers analyzed the chemicals emitted from the heads of 19 babies and detected hexadecanal in all but two, noting that the compound was one of the most abundant molecules they detected.

“Our results imply that sniffing babies may increase aggression in mothers but decrease aggression in fathers,” the researchers concluded in the paper. However, they acknowledge, this explanation “remains to be experimentally verified, and here serves only as an example of possible ecological relevance for our results.”

A story of smell

The research also had several other important limitations. Mishor’s team didn’t measure how much hexadecanal humans actually emit, or how this amount differs between babies and adults. It’s not clear yet under what circumstances adults release hexadecanal or how much of this molecule is inhaled by other people. And although the researchers identified brain activity patterns associated with exposure to hexadecanal, they didn’t show that this activity was actually responsible for making people behave more or less belligerently.

On top of all this, hexadecanal isn’t the only chemical that babies give off. To find out whether hexadecanal does indeed play a role in parental aggression, Mishor says, the team will need to test it along with the rest of the compounds in human baby odor.

The findings support the idea that hexadecanal is a pheromone, or substance that animals use to communicate with other members of their species. “The study moves us towards understanding how this chemical can affect human behavior,” says adds Royce Lee, an associate professor of psychiatry and behavioral neuroscience at the University of Chicago, who wasn’t involved in the research. “I wouldn’t go so far as to say that we know that this will affect parental behavior, or how we behave outside of the laboratory.”

It remains to be confirmed whether the sex difference that Mishor and her team observed would remain in future experiments with larger numbers of volunteers. More generally, claims on sex-based differences brain structure and activity have been shown to be largely unreliable, with recent research suggesting that our brains are individual “mosaics” of “female-typical and male-typical features.” “Nonetheless, Lee says, the results are “certainly very interesting and provocative.”

“One question is, does this give us some clues about what can reduce human aggression?” he says. “I could see one pathway in the future to study this chemical and to see if we can learn something about how to help with human aggressive behavior.”

Mishor, Lee, and Panigrahy all agree that the findings have implications for our understanding of the mysterious connection between the nose and brain.

“Human olfaction is one of the most primordial senses,” Mishor says. “It is wired differently in the brain than other senses, and it many times bypasses consciousness and impacts us without us being aware of the effect.”

The researchers focused on a very specific type of behavior in their experiments, raising the intriguing question of whether the chemical might be relevant for other kinds of social situations, notes Panigrahy, who is currently studying how olfaction influences social behavior in people who have congenital heart disease.

The findings may have particular resonance as the world continues to deal with COVID-19, which can impair people’s sense of smell, he says.

“This is a really important topic from the perspective of what we’re going through now,” Panigrahy says. “Understanding how olfaction relates to social behavior from a bigger context is so relevant to our current era.”

Source: A human pheromone could affect aggression | Popular Science

Recent pheromone-related articles

Humans can ‘smell’ each other’s emotions | Livescience

This article discusses the profound importance of the sense of smell in human relationships and social interactions. Chrissi Kelly, who lost her sense of smell after a viral infection, founded…

Sniffing body odour is tested as an anxiety therapy | BBC News

IMAGE SOURCE,GETTY IMAGES Sniffing other people's body odour might be useful in therapy for social anxiety, say Swedish researchers who have started tests with volunteers. The scientists have been using…

Does body odor indicate illness? What your smell says about you

The physician and biologist Hanns Hatt, professor at the Ruhr University Bochum, has been on the trail of the riddle of smell for decades. He decoded the first human olfactory…

Horses show ability to discriminate between human odors of fear and joy |

An example of one of the mares using her left or right nostril to sniff the sample. Photo: Plotine Jardat Horses are able to discriminate between human odors produced in…

Study Suggests Body Odor Can Reveal if a Man Is Single or Not | New Scientist

Photo: macniak/Depositphotos From our health to compatibility, our scent can say a lot about us. According to a new study, women can actually detect whether a man is single or…

Women can sniff out single men as scent reveals if you’re married, scientists claim | The US Sun

SNIFFING your date may not be the first thing you do but a study claims that women can actually smell if a man is married. According to scientific research based in Australia,…

Inside The Connection Between Scent And Attraction | Glam

Dragana Gordic/Shutterstock They say love comes down to chemistry. There's an undeniable, unexplainable "je ne sais quoi" when you meet "the one." Fragrance experts and scientists now believe that the chemical…

Dogs can smell when humans are stressed, study suggests | CTV News

Undated photo of a dog smelling. (Blue Bird/Pexels) Megan Marple There's now scientific evidence shedding more light on one of Barkley's impressive skills in a long list of endearing traits:…

Body odor sniffing linked to higher sex drive: study | Vigour Times

Sex smells! Enjoying the stench of body odor might not just be a bizarre fetish: Those who like whiffing other people’s natural aroma may have a higher appetite for sex…

T-Shirt Study Shows Importance of Mom’s Smell to Bond With Baby | Consumer Healthday

The sound of mom's voice can soothe a fussy baby like nothing else, but now new research suggests that an infant is also calmed by the scent of its mother.…

Viruses can change your scent to make you more attractive to mosquitoes, new research in mice finds | The Conversation

Mosquito-borne diseases are estimated to cause over 1 million deaths a year. mrs/Moment via Getty Images Mosquitoes are the world’s deadliest animal. Over 1 million deaths per year are attributed to mosquito-borne diseases, including…

Your Nose Knows: New Science Suggests Scents Matter to Humans as Much as to Dogs | The Epoch Times

(Adam Griffith) The human nose is not usually considered an asset. Most humans are more concerned with how our noses look than how they function, unless, that is, we’re plagued with sinus…

Does Your Nose Help Pick Your Friends? | New York Times

Credit...Robert Kneschke/Alamy In a small study, researchers in an olfaction lab found that people who had an instant personal connection also had similarities in their body odors. Human beings maintain…

Baby’s Superpowered Scent Can Manipulate Parents’ Moods, Researchers Find | VOA News Why would the smell of a baby's head calm men but rile women? It may be another example of how we're more animal than we like to think. Source:…

Medieval Aphrodisiacs: Body Scented Bread Dough! | Ancient Origins

People in Europe in the Middle Ages boosted libidinal sexual intimacy through the use of medieval aphrodisiacs, some of which are truly bizarre. Dr. Eleanor Janega, a medieval historian based…

Newborn babies’ smell has opposite effects on parents – study | JPost

Mother with newborn baby in the nursing pillow. (photo credit: INGIMAGE) Parents of newborn infants invariably gush: “There’s nothing like the smell of my baby!” But this is no mere…

Why Someone’s Scent Can Be A Make Or Break Factor In Creating Connection | The Zoe Report

Scent & Attraction Psychology — Why They Are So Connected When it comes to attraction, a lot of factors come into play, from physical to mental. But there’s one crucial…

T-Shirt Study Shows Importance of Mom’s Smell to Bond With Baby | HealthDay

Adobe Stock MONDAY, Dec. 13, 2021 (HealthDay News) -- The sound of mom's voice can soothe a fussy baby like nothing else, but now new research suggests that an infant…

A human pheromone could affect aggression | Popular Science

We're just starting to understand how smell can change human behavior. Unsplash Scientists observed how people reacted to frustrating computer games in the presence and absence of the molecule, known…

Yes, dogs can ‘catch’ their owners’ emotions | National Geographic

A girl and her dog in Boone County, West Virginia.PHOTOGRAPH BY STACY KRANITZ A pile of recent studies show how canines pick up chemical and physiological cues from people that…

Is there a biological basis for instant attraction? | New York Post

Is there a biological basis for instant attraction? New finings in mice has revealed an instinctual preference for those with similar genes.Getty Images Scientists are getting closer to identifying a…

Your dog has a rich interior life it’s not telling you about |

Gossiping Malamutes (Getty Images) From conveying personal data via scents to using body language to "speak," dogs are secretly great communicators Dogs and humans have co-evolved to the point that…

Why single people smell different | BBC

(Image credit: Michal Bialozej) By William Park There is a wealth of psychological and biological information stored in our scent, but for some reason we choose to ignore it. King…

Is an irresistible human pheromone possible? | Whyy

(Sergio Mazurini /Big Stock Photo) This story is from The Pulse, a weekly health and science podcast. Researcher Jessica Gaby says it’s about time those who lack deep human connections in life start…

Dogs that detect seizures may be sniffing out the scent of human fear | New Scientist

Dogs may be able to recognise the “smell of fear” Description:Credit: plainpicture/Mölleken Dogs that can predict when their owners are going to have an epileptic seizure may be recognising the…

Honeybees Use Scent Maps to Keep Track of Their Queen | Discover Magazine

(Credit: Samo Trebizan/Shutterstock) Honeybees can find their way back to their queen using a sophisticated form of the telephone game. Even after foraging for hours, they can smell the pheromones…

Bees form scent-driven phone tree to pass along messages | EurekAlert! Science News

Honeybees play a scent-driven game of telephone to guide members of a colony back to their queen, according to a new study led by University of Colorado Boulder. The research,…

Vagina-scented face masks | Boing Boing

Photo: Cottonbro / Pexels Samantha Cole reports on a pandemic trend that's nothing to sniff at: vagina-scented face masks.For fetish item sellers, the pandemic is an opportunity for a new kind…

Love Is an Emotion That Dogs Can Smell – Bioesse Develops Groundbreaking Inhalation Technology That Uses Pet-Owners’ Scent to Virtually Eliminate Canine Anxiety Issues in Normal, Healthy Dogs | PR Newswire

My Pet–My Scent. Bioesse Technologies Bioesse ( recently announced that it had researched, developed and patented a product that could nearly eliminate the daily canine anxiety-related issues experienced by average,…

Roane Co. widow helps strangers cherish the memory of their lost loved ones | WBIR

Juanita Jackson sews 'Memory Bears' out of articles of clothing to give comfort to people grieving from the death of a loved one. ROANE COUNTY, Tenn. — In an exclusive…