Tag Archives: smell


The human tongue can actually ‘smell’ things

New research shows that the senses or taste and smell are much more intertwined than we’ve previously thought.


Image via Pixabay.

A team of researchers from the Monell Center report finding functional olfactory receptors — the sensors that detect odors in the nose — in the taste cells of our tongues. The findings suggest that the interactions between smell and taste, both of which comprise flavor, may actually begin on the tongue and not in the brain.

Smelling strawberries

“Our research may help explain how odor molecules modulate taste perception,” said study senior author Mehmet Hakan Ozdener, MD, PhD, MPH, a cell biologist at Monell.

“This may lead to the development of odor-based taste modifiers that can help combat the excess salt, sugar, and fat intake associated with diet-related diseases such as obesity and diabetes.”

You know how we recognize that something smells like strawberries, even though strawberries themselves don’t have a smell when you sniff them? This shows you how smell helps create flavor.

The sense of taste handles sweet, salty, sour, bitter, and umami (savory) molecules on the tongue. It evolved as a quick way for our brains to figure out how nutritious something we’re chewing on is, and make sure it’s not toxic or poisonous. But smell, too, was an important part in detecting the next snack. A pear and an apple taste pretty much the same if you hold your nose while eating. What our brains do when we eat something is to combine taste and smell, alongside information from other senses, to create what we perceive as flavor.

Common wisdom held that information from taste and smell stays separate until reaching the brain. However, Ozdener realized no one has previously checked this assumption. He thought of this when when his 12-year-old son asked him if snakes extend their tongues so that they can smell. So, alongside colleagues at Monell, Ozdener set about culturing living human taste cells.

After developing the techniques that would allow them to maintain such a culture, the team probed the cells, finding many of the molecules present in human olfactory receptors. Next, they employed calcium imaging to show that these cells respond to odor molecules in a manner similar to olfactory receptor cells. Taken together, the data points to olfactory receptors playing a role in our taste systems — possibly by interacting with taste receptors on the tongue. Other experiments by the Monell scientists demonstrated that a single taste cell can contain both taste and olfactory receptors, which supports the present findings.

“The presence of olfactory receptors and taste receptors in the same cell will provide us with exciting opportunities to study interactions between odor and taste stimuli on the tongue,” said Ozdener.

The findings help us better understand how smell and taste interact. However, they could also better inform us about either of those senses individually. We still don’t know, for example, what compounds activate the vast majority of the 400 types of functional human olfactory receptors. The cells cultured by the team, which respond to odors, could be used to screen molecules that bind to such receptors.

The paper “Mammalian Taste Cells Express Functional Olfactory Receptors” has been published in the journal Chemical Senses.

Some COVID-19 patients don’t recover their sense of smell or taste after all other symptoms go away

Almost 90% of those who lost their taste and smell after falling ill with COVID-19 fully regained them or improved within a month. But about 10% of such cases never regained the two senses during the study’s observation period, highlighting long-term problems that the virus could bring.

Credit Flickr

An international team of researchers studied a group of 202 Italians that were infected but weren’t ill enough to be hospitalized. They were asked to rate their sense of smell or taste after being diagnosed and then again a month later through phone interviews. A six-point scale was used, scoring 0 for no problem and 5 for complete loss of the sense.

The loss of the sense of smell or taste was recognized as one of the core symptoms of people infected with the coronavirus. It was first observed in hospitalized patients but then also in those with mild disease. While understanding is limited, initial studies suggested that this could be caused by the disruption of cells that support olfactory neurons.

The study found that 113 of the patients – about two-thirds – reported loss of taste and/or smell up to two weeks before they tested positive. Of that total, 55 said they had recovered fully, 46 reported improvements in their symptoms and 12 said their symptoms were unchanged or worse.

“Although altered sense of smell or taste showed an improvement in most cases during the course of the disease, these symptoms were still the most frequently reported by patients with COVID-19 4 weeks after testing,” the researchers wrote. “However, the persistence of altered sense of smell or taste was not associated with the persistence of the SARS-CoV-2 infection at control swab”

The median length of time the patients went without being able to smell or taste at all was a little more than 11 days, according to the findings. There was no correlation between those patients who again tested positive for COVID-19 four weeks after their initial diagnosis and those who were still having trouble smelling or tasting at this point.

The researchers believe this means an active loss of one or both of those senses cannot be considered proof of an active COVID-19 infection, theorizing that it takes the body some time to “repair and regenerate” the senses regardless of whether the virus has left the body.

Age and sex were not found to be significant factors affecting the rate of recovery from anosmia or dysgeusia. However, those patients who reported the most significant losses of smell and/or taste also tended to report the worst recoveries after four weeks – again suggesting that it takes the body time to reverse the damage done to the senses by COVID-19.

“Even with a high rate of resolution, the staggering number affected by this evolving pandemic suggests an almost certain deluge of patients likely to present for the treatment of unresolved symptoms,” Dr. Joshua Levy of the Emory University School of Medicine in Atlanta and co-author. said in a statement

Levy suggested that in long-term cases, people could consider therapy such as smell-training to help restore the senses. UK Professor Claire Hopkins, one of the researchers behind the study, said the team is now conducting more research on people with long-lasting symptoms.

“For people who recover more quickly it is likely the virus has only affected the cells lining their nose,” she told the BBC. “For people who recover more slowly it may be that the virus has affected the nerves involved in smell, too. It can take longer for these nerve cells to repair and regenerate.”

The study was published in the journal JAMA.

Nosy study finds we probably produce new neurons all the time

New research suggests that humans may actually be able to create new neurons after childhood. The paper reports on a new “neuron nursery” located in a section of our noses.

Human olfactory neuroepithelium.
Image credits Duke University.

The study was published in the context of a much wider (and long-lasting) debate on whether humans are able to create new neurons after the age of 13. Neurons, the ultra-specialized cells that underpin our nervous systems, aren’t only useful for thinking or telling muscles to move. The current study focuses on neurons that act as receptors in the olfactory neuroepithelium of the nose. These neurons directly underpin our ability to smell.

Smells brand new

“We do not fully understand why people lose their sense of smell, which can occur for many reasons, and our data sets provide a wealth of information about the cell populations present in adult olfactory tissue,” said Brad Goldstein, M.D., Ph.D., an associate professor and vice chair for research in the Department of Head and Neck Surgery and Communication Sciences at Duke University and senior author of the study.

“This is an important step in developing treatment strategies for conditions when this tissue may be damaged.”

This study is the first of its kind to use human tissue samples (previously only mice nasal tissue samples were used). Starting from them, the team found that immature neurons being produced by stem cells made up over half of the number of neurons in the samples, suggesting that they were actively being produced there. Which, obviously, means that neurons can be produced throughout our lifetime.

Hiroaki Matsunami, Ph.D., a professor in the Department of Molecular Genetics and Microbiology at Duke University and co-author on the paper, explains that the molecular make-up of these immature neurons point heavily to them being grown there during adulthood.

The team says that their findings could help guide treatment options for conditions that cause smell damage or loss, but could in time be applicable to the nervous system as a whole.

“It will be very useful to use this window to analyze samples from people with conditions in which the nervous system has degeneration, such as Alzheimer’s disease,” said Goldstein.

“Alzheimer’s is of particular interest, since these patients lose their sense of smell quite early in the disease process, and we have few treatments for Alzheimer’s disease. So, it may make sense to look carefully at regions of the olfactory system in these patients.”

The nose is a very exposed site, the team adds, meaning that in time we could learn how to collect neuronal stem cells from the area and use them to treat other disorders involving the nervous system.

“It is not outside of the realm of possibility,” said Matsunami.

The paper “Single-cell analysis of olfactory neurogenesis and differentiation in adult humans” has been published in the journal Nature Neuroscience.


Unpleasant smells make for more powerful memories, a new study finds

Stinky smells make for stronger memories, it seems.


Literally unforgettable.
Image via Pixabay.

New research from the New York University’s Department of Psychology suggests that memories are stronger when the original experience was accompanied by unpleasant odors. The findings broaden our understanding of the mechanisms that underpin memory and of how negative experiences help shape our ability to recall past events.

Smells… familiar

“These results demonstrate that bad smells are capable of producing memory enhancements in both adolescents and adults, pointing to new ways to study how we learn from and remember positive and negative experiences,” explains Catherine Hartley, an assistant professor in New York University’s Department of Psychology and the senior author of the study.

“Because our findings spanned different age groups, this study suggests that aversive odors might be used in the future to examine emotional learning and memory processes across development,” adds lead author Alexandra Cohen, an NYU postdoctoral fellow.

Negative experiences are known to impact our memory. If you get bitten by a dog, for example, you can develop a negative memory of that particular animal — and that negative association may eventually eneralize to all dogs. You’re also much more likely to have a vivid, powerful memory of that particular interaction than your other past experiences with dogs due to the trauma associated with the event.

“The generalization and persistence in memory of learned negative associations are core features of anxiety disorders, which often emerge during adolescence,” notes Hartley.

In order to get a better idea of how these learned negative associations shape the way our memories form during this age, the team designed and administered a Pavlovian learning task to individuals aged 13 to 25. Such tasks usually employ mild electrical shocks; however, the researchers used bad smells because they can be ethically administered in studying children.

The task included viewing a series of images belonging to one of two conceptual categories: objects (e.g., a chair) and scenes (e.g., a snow-capped mountain). Participants wore a nasal mask connected to an olfactometer (an instrument used to detect and measure odor dilution) as they viewed the images. When images from one category were shown, participants were given unscented air. While participants viewed images from the other category, unpleasant smells were sometimes circulated through the device to the mask.

In order to determine which odors the participants found unpleasant, the researchers had the subjects breathe in a variety of odors and indicate which ones they thought were unpleasant prior to the study. The odors were blends of chemical compounds provided by a local perfumer and included scents such as rotting fish and manure.

This allowed the team to quantify the effect of a bad smell on individual memories as well as generalization to related images. In other words, they could measure if the image of a chair was stronger when associated with a bad smell, and whether this would happen only for this image or images in general. The team measured perspiration in the participants’ hands as a proxy for arousal levels. One day after the task, researchers tested participants’ memory for the images.

Their findings showed that both adolescents and adults showed better memory specifically for images paired with the bad smell 24 hours after the task. They also found that individuals with higher arousal levels during while viewing images that may have been associated with an unpleasant smell had better memory of the images 24 hours later regardless of whether or not a smell was actually delivered. This suggests that unpredictability or surprise associated with the outcome leads to better memory.

The paper “Aversive learning strengthens episodic memory in both adolescents and adults” has been published in the journal Learning & Memory.


Heavy coffee drinkers can smell its aroma much easier than other people — and it seems tied to craving

Regular coffee drinkers can perceive the smell of coffee with surprising alacrity, a new study reports. Compared to non-coffee drinkers, they’re also faster at recognizing the aroma, it adds.


Image credits Karolina Grabowska.

Those who make a habit out of drinking coffee are more sensitive to its odor and are faster to identify its aroma. Additionally, their ability to sniff out the bean also increases the more they crave coffee. This study, its authors write, provides the first evidence that coffee addicts are more sensitive to the smell of coffee than the rest of us. While the team worked with coffee, their findings should be broadly applicable to other substances with a distinct smell — for example, the findings could help design new aversion therapies for people addicted to tobacco or cannabis in addition to coffee.

Brewed to perfection

“We found the higher the caffeine use, the quicker a person recognised the odour of coffee,” says Dr. Lorenzo Stafford, an olfactory expert in the Department of Psychology at the University of Portsmouth, and lead author of the paper.

“We also found that those higher caffeine users were able to detect the odour of a heavily diluted coffee chemical at much lower concentrations, and this ability increased with their level of craving. So, the more they desired caffeine, the better their sense of smell for coffee.”

The team explains that drug cues (such as the smell of an alcoholic beverage) can trigger cravings in users. However, the team wanted to check if the relationship works the other way around: whether or not people who are big coffee drinkers can more readily perceive and respond to the smell of coffee. Their study is the first to show that this is true, at least with mildly-addictive drugs such as coffee. The more we want that cup of warm goodness, the better we are at sniffing it out wherever it may hide. The results suggest heavy coffee drinkers were more sensitive to the smell of coffee, and that the smell is linked to their cravings.

“Caffeine is the most widely consumed psychoactive drug and these findings suggest that changes in the ability to detect smells could be a useful index of drug dependency,” Stafford says.

The study was based on two experiments. In the first one, 62 men and women were divided into three groups: those who never drank anything with caffeine, and those who consumed some (70-250mg, equivalent to 1-3.5 cups of instant coffee a day), and those who consumed a high amount (300mg, equivalent to 4 or more cups of instant coffee a day).

Each participant was blindfolded and asked to pick out traces of coffee odor from odor blanks (a substrate with no smell). For this test, participants were asked to identify the scent of real coffee as quickly as possible. As a control test, participants were also asked to perform the same task with essential lavender oil.

Those in the heavy coffee drinker group were able to correctly identify the smell of coffee at weaker concentrations than their peers and were faster to do so.

“More interestingly, higher craving, specifically that which measured the ability of caffeine to reverse withdrawal symptoms such as fatigue, was related to greater sensitivity in the odour detection test,” Dr. Stafford said.

In the second test, 32 people (not involved in the first experiment) were divided into two — one coffee-drinker, one non-coffee-drinker — groups. They were put through the same odor detection test for coffee, this time with the control involving non-food odors. Here, too, coffee consumers were more sensitive to the coffee smell, but not to the non-food odors.

Overall, the findings suggest that our sensitivity to particular smells is linked to cravings and that this could be used to break some drug use behaviors. Previous research has shown that training people to associate an odor with something unpleasant showed greater discrimination to that odor, which could be used to help them steer clear of certain substances.

The paper “Higher olfactory sensitivity to coffee odour in habitual caffeine users” has been published in the journal Experimental and Clinical Psychopharmacology.

Scientists draw inspiration from nature to develop cheese-smelling electronic nose

Dogs are not only man’s best friend, but they’re also amazing sniffers. Their ability to detect explosives or illegal substances has long been understood but we’re just scratching the surface. Recent studies have shown that dogs are able to detect several types of cancer, malaria, and even so-called superbugs. Researchers are now trying to find new ways to replicate these abilities in sensors and robots.

“We turned to animals to understand what nature has already figured out,” said Thomas Spencer, a doctoral candidate in David Hu’s lab at Georgia Tech. “We are applying the underlying principles that we learned about these mechanisms to design a better sensor.”

An electronic nose

Spencer and colleagues work on designing the electronic equivalent of a nose — and they started out with a cheese smelling competition — how else? At the current stage, the team focused on how to best drive the odor to the sensor, a natural process in the biological world, but one that’s quite tricky to replicate electronically.

Dogs aren’t the only creatures with amazing sniffing abilities, and researchers wanted to see which animals fare best in this regard. To this aim, they traveled to the Atlanta Zoo to compare the way different animals sniff, from mice to elephants.

“We wanted to measure the sniffing frequency of animals when they are trying to identify a new source of food or something that interests them,” Spencer said.

Unsurprisingly, they found that sniffing speed decreases with body size — in other words, small creatures like mice sniff much faster than large creatures like elephants.

In order to figure this out, the team used wind tunnel experiments to map how the odor particles moved through the air. The team gathered sensor information in real time, analyzing how chemical compounds shift around during the sniffing process and then developed computer simulations to refine the observations.

“These findings are important because it gives us insight into the physics of sniffing,” said Hu, an associate professor of mechanical engineering and biology at Georgia Tech. “This information will affect how we scale up sniffing machines.”

Kelly the elephant searching for food above eye level using her trunk. Image credits: Thomas Spencer.

Using these insights, they were able to design an electronic nose that distinguishes from different types of cheese — still a far cry from what dogs can do, but a great step in the right direction.

So far, results are only preliminary and have not been published in a peer-reviewed journal. The study will be presented at American Physical Society’s Division of Fluid Dynamics 71st Annual Meeting.

“This is still a fairly new study,” Spencer said. “Our hope is to get a snippet of that ability and replicate it for ourselves.”

The European sea bass (Dicentrarchus labrax). Credit: Citron, Wikimedia Commons.

Fish are losing their sense of smell because of acidic oceans

Most of the carbon dioxide (CO2) associated with human activity is absorbed by the oceans, which act as a huge carbon sink. In doing so, the oceans help curb global warming by keeping greenhouse gases from trapping heat in the atmosphere but on the downside, CO2 and seawater react to form carbonic acid — which makes the water more acidic.

Among the many potential problems this causes to marine life, a new study found that the increasingly acidic oceans are making fish lose their sense of smell.

The European sea bass (Dicentrarchus labrax). Credit: Citron, Wikimedia Commons.

The European sea bass (Dicentrarchus labrax). Credit: Citron, Wikimedia Commons.

Olfaction is key in order for fish to find food and safe habitats, avoid predators, and to recognize each other. Dr. Cosima Porteus, a researcher at the University of Exeter, and colleagues are the first to examine the impact of rising CO2 in the ocean on the olfactory system of fish.

In collaboration with researchers at the Centre of Marine Sciences (CCMar, Faro, Portugal) and the Centre for Environment, Fisheries and Aquaculture Science (Cefas), the team compared the behavior of juvenile sea bass that swam in water of various acidity, including values which scientists predict for the end of the century if current trends continue unabated. 

Since the Industrial Revolution in the 18th century, oceanic CO2 has risen by 43% and, by the end of the century, scientists predict it will grow by another 250%.

The results of their experiments suggest that the fish in acidic waters swam less and were less likely to respond to olfactory stimuli such as the smell of a predator. These kind of fish were also more likely to “freeze”, which is a sign of anxiety.

Elevated CO2 reduces the active space (represented by the blue sphere) of an odour by up to 80% (represented by the yellow dashed line) and the distance to a detectable odour source (arrow) by up to 42% in European sea bass. Credit: Nature Climate Change.

CO2 reduces the active space (represented by the blue sphere) of an odor
by up to 80% (represented by the yellow dashed line) and the distance
to a detectable odor source (arrow) by up to 42% in European sea bass. Credit: Nature Climate Change.

To objectively measure the sea bass’ ability to detect different smells, the researchers recorded the activity of their nervous system while the nose of the fish was exposed to water of different CO2 concentrations and acidity.

“The sense of smell of sea bass was reduced by up to half in sea water that was acidified with a level of CO2 predicted for the end of the century. Their ability to detect and respond to some odours associated with food and threatening situations was more strongly affected than for other odours. We think this is explained by acidified water affecting how odorant molecules bind to olfactory receptors in the fish’s nose, reducing how well they can distinguish these important stimuli. Therefore, rising atmospheric CO2 levels threaten natural aquatic ecosystems and our food supply,” said Dr. Porteus in a statement.

[panel style=”panel-success” title=”Oceanic acidity is on the rise ” footer=””]At least one-quarter of the carbon dioxide (CO2) released by burning coal, oil and gas doesn’t stay in the air but instead dissolves into the ocean. Since the beginning of the industrial era, the ocean has absorbed some 525 billion tons of CO2 from the atmosphere, presently around 22 million tons per day.[/panel]

A poorer sense of smell is just one of many negative effects of oceanic acidification — which is sometimes called ‘climate change evil’s twin’. Take us humans, for instance, whose normal blood pH ranges between 7.35 and 7.45. Just a slight drop in blood pH of 0.2-0.3 can cause seizures, comas, and even death. Likewise, even a small change in seawater acidity can have harmful effects on marine life, impacting chemical communication, reproduction, the nervous system, and growth.

For some creatures, increasing ocean acidity is worse than in others. Because of lower pH of seawater, carbonate ions bind together, making them less readily available for corals, oysters, mussels, and many other shelled organisms that need them to build shells and skeletons. What’s more, ocean acidification causes coral bleaching by expelling the symbiotic algae living in their tissue, turning them white and subject to mortality.

“Our intriguing results show that CO2 impacts the nose of the fish directly. This will be in addition to the impact of CO2 on their central nervous system function suggested by others previously, which proposed an impaired processing of information in the brain itself. It is not yet known how rapidly fish will be able to overcome these problems as CO2 rises in the future. However, having to cope with two different problems caused by CO2, rather than just one, may reduce their ability to adapt or how long this will take,” Prof. Rod Wilson from the University of Exeter commented in a statement. 

Perhaps, fish will have the chance to evolutionary adapt by the end of the century — but that seems unlikely. The team also studied the genes that are expressed in the nose and brain of sea bass, looking for any changes in response to elevated CO2 and acidity in the water. Strikingly, instead of finding some compensation for the sea bass’ reduced sense of smell, the researchers found evidence of reduced expression of genes for smell receptors in the nose, which actually makes matters worse. Although only the genes of sea bass were analyzed, many species share the same genes and smell receptors and, therefore, the findings should apply more broadly.

The findings appeared in the journal Nature Climate Change.


Mosquito swarm.

Malaria makes its hosts smell better to draw more mosquitoes, research finds

Malaria can change the way you smell, drawing more mosquitoes, a new study shows. The results might explain how the disease is able to spread so effectively.

Mosquito swarm.

Image credits Petra Boekhoff / Pixabay.

Malaria, a disease caused by the parasite genus Plasmodium and spread by mosquito bite, could make you more attractive to the insects. Its findings come to flesh out previous research which found that the parasites change the smell of animals they infect. The work also shows one of Plasmodium‘s more insidious mechanisms, in which it lures mosquitos in towards infected individuals, super-charging its spread.

Maybe she’s born with it, maybe it’s malaria

The research, led by Ailie Robinson from the Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, tested participants outside of the lab, dissecting their body odors to see which elements of its chemical makeup matter to mosquitoes.

The team’s smelly research brought them in contact with the socks of 45 Kenyan schoolchildren — some of them infected by malaria, others not. To see whether mosquitos displayed any preference towards the smell of those infected with Plasmodium, the team placed socks in a test device, formed out of two boxes linked by a tube. Then, they released mosquitos into the tube and tracked which sock they flew toward.

The insects showed a preference for the socks worn by infected children, the team reports. When presented with a choice between these socks and ones worn by the same child 3 weeks after the infection was treated with medication, 60% of the mosquitos chose the ‘infected’ sock. When presented with two pairs of socks collected at different times from children that were never infected, the mosquitoes didn’t show any preference one way or the other.

Now that they knew something in the scent of malaria-infected individuals made them more attractive to mosquitos, the team wanted to find out exactly what that ‘something’ was. They analyzed foot odor samples obtained from 56 children, obtaining the full list of chemicals that constituted the scents. Then, they puffed each chemical at a time over mosquito antennae attached to electrodes.

This testing zeroed in on aldehydes, a class of chemicals including heptanal, octanal, and nonanal — organic molecules constructed out of chains of seven, eight, and nine C atoms respectively, which impart fragrance to spices, fruits, and perfumes among others. These compounds were found in higher levels in the samples of infected children and elicited a strong electrical response from the antennae.

‘Smells like something I’d bite’

It’s possible that malaria is promoting its spread by making the scent of infected individuals more alluring to mosquitoes. The more insects that the plasmodium can goad into biting these individuals, the more chances the infection has of spreading to other people says study co-leader James Logan, a medical entomologist at the London School of Hygiene & Tropical Medicine.

However, the team isn’t certain what’s behind this difference in odor. It could be that the aldehydes are secreted by the parasite itself, or that they may be produced when the host’s fat cells break down during the infection, the team notes. They caution, however, that while the come-hither effect may be unique to malaria, it’s possible the shift in odor is common to other diseases as well.

“The malaria parasite is sort of manipulating the system both in the mosquito host and the human host,” Logan says. “It’s very clever.”

“This is probably specific to malaria, but it could be that other infections could cause the same effect.”

Understanding odor’s effect in the spread of malaria could help us detect infection sooner and nip its transmission in the bud. Alternatively, it could lead to the creation of better mosquito traps. Getting the bouquet just right is quite tricky, though — the team notes that even small tweaks in scent mixes they produced in the lab will influence whether mosquitos are piqued or indifferent. In one seemingly paradoxical case, the insects were drawn to a scent spiked with a small dose of heptanal, but decidedly unimpressed when the amount of the chemical was increased slightly.

The paper “Plasmodium-associated changes in human odor attract mosquitoes” has been published in the journal Proceedings of the National Academy of Sciences.

Dog nose.

Dogs create a mental image of what they’re sniffing for

Dogs will be surprised, and a little confused, if the scent they’re trailing doesn’t match what they find.

Dog nose.

Image via Pixabay.

Dogs are awesome. Not only are they fluffy and quite cute, but they can also use their noses in ways that put us simple bipeds to shame. However, while the keenness of their scent has been known since antiquity, the question of whether or not they understand what they smell hasn’t been answered.

A smelly type of smell

That’s what a team of researchers from the Max Planck Institute and the Friedrich Schiller University of Jena set out to discover, and their results suggest that dogs create a “mental representation” of what they’re tracking via scent trails. This means that our furry friends understand what they’re sniffing, form an expectation of the ‘target’, and will show confusion if that expectation isn’t met.

[Further Reading] They also hate hugs.

The team worked with 48 dogs, 25 of whom had undergone training either with the police or as part of a rescue team, while the other 23 were family pets without any special training. The canines first participated in a pre-test, during which the team identified two toys that each dog showed a preference for when asked to retrieve.

For the study proper, each underwent four trials. The dogs were tasked with following a scent trail drawn with one of the two toys for each trial. At the end of the scent trail (in an adjacent room) the dogs found either the toy used to lay down the trail (normal condition) or the other one identified in the pre-test phase (surprise condition). Half of the dogs involved in the study were allocated to the normal condition, half to the surprise condition.

“From my experience in other studies, I had assumed that the surprise would be measurable, in that the dogs would behave differently in the surprise condition than they would in the normal condition,” explains lead researcher Dr. Juliane Bräuer.

“In fact, quite a few dogs showed interesting behavior, especially in the first round of the surprise condition, which we called ‘hesitation:’ although they had obviously noticed the toy, they continued to search via smell, probably for the toy that had been used to lay the scent trail.”

This surprising effect was short-lived, however: while the animals hesitated in the first test, they went right ahead in subsequent runs. The team believes this could come down to the nature of the study, as the dogs were rewarded by playing games no matter which toy they found, which positively reinforced retrieving. Alternatively, it could come down to smell contamination from previous test runs that permeated the room, despite the researchers’ efforts to clean it.

Still, Dr. Bräuer believes the results of the first round are a solid indication that dogs form a mental representation of the target they’re sniffing out, which means they have a concrete expectation of what they’re going to find.

Finally, the team reports that while police and rescue dogs were expected to (and did) retrieve the toys faster than family dogs, by the fourth round the two groups performed equally — an effect that Dr. Bräuer remarks as “interesting”. Next, the team is going to focus on clarifying the connection between smell, search behavior, and cognition in dogs.

The paper “A ball is not a Kong: Odor representation and search behavior in domestic dogs (Canis familiaris) of different education” has been published in the Journal of Comparative Psychology.

Your reaction to smells could say a lot about your political preference, a new study suggests

A surprising study has found that people who are easily disgusted by strong odors like sweat or urine tend to prefer more authoritarian leaders, and it might all have a lot to do with diseases.

Image credits: Hanna Esser.

Disgust is a basic emotion, and it was a very important tool for survival over countless generations. Disgust is basically a way of saying “I’ll have none of that,” and it’s most commonly related to nasty smells or foods.

Just think about someone being disgusted — it has a lot to do with a person’s senses. The nose is wrinkled or turned away, the eyes partially or entirely closed. The whole body is shutting down its sensorial information, and for a good reason: many things that are disgusting are rotten, dirty, or infectious — you don’t want to be near them, and you certainly don’t want to smell or eat them. Disgust is useful largely because it helps you avoid potential diseases, but different people have different tolerance levels.

Researchers had an idea that there would be a connection between how people are disgusted by smell and how they want their country to be led. The idea is that people who have a strong urge to avoid unpleasant smells would also avoid mingling with other groups of people such as immigrants. They would be against multiculturalism and would fall towards the authoritarian side of the political spectrum, researchers suspected. They were right.

‘There was a solid connection between how strongly someone was disgusted by smells and their desire to have a dictator-like leader who can supress radical protest movements and ensure that different groups “stay in their places”. That type of society reduces contact among different groups and, at least in theory, decreases the chance of becoming ill’, says Jonas Olofsson, who researches scent and psychology at Stockholm University and is one of the authors of the study.

Among other questions, researchers asked international participants to rate their levels of disgust for body odors, both their own and others and then gauged their political preferences, looking for correlations.

While seeming completely unrelated, the connection between smell and politic inclinations does make a lot of sense. After all, if disgust is a means of isolating yourself from unwanted, potentially dangerous, then people who are more easily disgusted might also want to be more isolated from other people which they consider as potentially dangerous. Isolationism and a negative attitude towards immigrants and different groups of people is a trademark of authoritarian governments. Still, it’s remarkable that such a clear correlation can be established between odors and ideology.

’Understanding the shared variance between basic emotional reactivity to potential pathogen cues such as body odours and ideological attitudes that can lead to aggression towards groups perceived as deviant can prompt future investigations on what are the emotional determinants of outgroup derogation. In the next future, this knowledge might inform policies to prevent ethnocentrism’ says Marco Tullio Liuzza from Magna Graecia University of Catanzaro, Italy, also one of the authors.

US participants who were easily disgusted by smells were more likely to vote for Trump — which perfectly fits the theory. Image credits: Gage Skidmore.

Notably, researchers also added an extra question for US participants: how they will vote in the 2016 presidential election. Since Donald Trump ticks the boxes for authoritarianism, he was an excellent example to test the theory. Lo and behold, people who dislike bodily odors the most were more likely to vote for Trump.

This is interesting because Trump himself has often said that other people disgust him physically, and is reportedly obsessed with hygiene.

‘It showed that people who were more disgusted by smells were also more likely to vote for Donald Trump than those who were less sensitive. We thought that was interesting because Donald Trump talks frequently about how different people disgust him. He thinks that women are disgusting and that immigrants spread disease and it comes up often in his rhetoric. It fits with our hypothesis that his supporters would be more easily disgusted themselves’, says Jonas Olofsson.

This seems to suggest that authoritarian beliefs are heavily ingrained in some people’s brains, similarly to smell preferences.

‘The research has shown that the beliefs can change. If contact is created between groups, authoritarians can change. It’s not carved in stone. Quite the opposite, beliefs can be updated when we learn new things.’

However, Jonas Olofsson is optimistic. The most important thing is to keep a communication channel between opposing groups, and change can happen, he says.

‘The research has shown that the beliefs can change. If contact is created between groups, authoritarians can change. It’s not carved in stone. Quite the opposite, beliefs can be updated when we learn new things.’

Journal Reference: Liuzza et al. Body odour disgust sensitivity predicts authoritarian attitudes.

Waving away mosquitoes teaches them to stop bothering prey

A female mosquito dining at a fancy… human?
Source: Pixabay/skeeze

Mosquitoes rely on smell to choose victims. In a new study published in Current Biology, mosquitoes learned to associate smells with vibrations mimicking human hand movements. After subsequent exposures to the same smell, the arthropods avoided the respective odor. This behavior suggests that the insects learned that certain scents were associated with a near-death experience.

The smell of fear

Mosquitoes, these tiny, annoying vampires, bother everyone from birds to humans. They are not just terribly vexing, but dangerous as well. Even though the word ‘mosquito’ comes from Spanish and means ‘little fly’, the insects are not innocent at all. Mosquitoes are considered the deadliest animals on Earth, causing 725,000 deaths per year, according to a 2014 World Health Organization survey. Malaria, a mosquito-borne infectious disease, killed 445,000 people in 2016, states WHO.

These alarming numbers are the main reason why scientists are now trying to come up with different methods to reduce mosquito bites.

Previously, researchers discovered that each mosquito species shows a proclivity towards a certain type of host animal, even towards distinct individuals within those species. Unfortunately, the exact mechanisms through which this insect chooses its prey are still unknown. For example, generalist mosquito Culex tarsalis primarily torments birds in the summer but feeds on both mammals and birds in the winter.

Researchers at the University of Washington conducted an experiment to see if mosquito preferences could be learned. The team, led by Jeffrey Riffell, employed mosquitoes, rats, chickens and a machine named the “vortexer”. Scientists first presented the insects with an animal smell — a rat, for example. Next, the vortexer was used to inflict small mechanical shocks on mosquitoes.

A mosquito in the “vortexer” machine, which simulates swats. (Image: Kiley Riffell)

The following step was to assess if the mosquitoes learned something. Two groups of mosquitoes took part in the study: a control group of untrained mosquitoes and a group of previously trained ones. Researchers discovered that trained mosquitoes did not attack the rats, as the untrained ones did. When scientists repeated the experiment — but this time with chickens — they observed that the Aedes aegypti mosquitoes encountered some difficulty acquiring avian odors. The reason might be that the Aedes aegypti mosquitoes predominantly suck human blood, so they would be inclined to learn mammal smells faster.

“Once mosquitoes learned odors in an aversive manner, those odors caused aversive responses on the same order as responses to DEET, which is one of the most effective mosquito repellents,” said Riffell in a statement. “Moreover, mosquitoes remember the trained odors for days.” he added.

Scientists wondered how the small mosquito brain could process such a large amount of information. One answer came to mind: dopamine, a neurotransmitter that is frequently used in learning processes (especially in remembering with the help of good or bad stimuli) by mammals and insects alike.

The team had one more thing to do: to prove their theory right. So, they genetically engineered mosquitoes that lacked dopamine receptors and glued them to a rack in order to monitor their neuron activity when introducing them to different odors. The researchers discovered that neurons were less likely to fire when presented various smells due to their inability to process dopamine.

A mosquito glued to a 3D-printed rack. (Image: Kiley Riffell)

“By understanding how mosquitoes are making decisions on whom to bite, and how learning influences those behaviors, we can better understand the genes and neuronal bases of the behaviors,” said Riffell. “This could lead to more effective tools for mosquito control.”

So, if a mosquito is troubling you, feel free to wiggle your hands at it. You might not kill it, but there is a good chance it will leave you alone.

Smelling your partner’s shirt will reduce stress, but a stranger’s will wind you up more

Women feel calmer after being exposed to their male partner’s scent, new research has found. The improvement was observable in their cortisol levels during mock stress trials.


Image credits Alterio Felines.

Smell is a powerful driver of emotion and memory. Just a whiff of something your parents used to cook is enough to yank you back to your childhood days, and a hint of a lover’s perfume enough to put the spring back in your step. New research shows that smell can also be a very powerful weapon against stress. The scent of your partner can help lower levels of the stress hormone cortisol even when they’re not there. But beware — the scent of a stranger had the opposite effect.

Benefits you can smell

Authors recruited 96 opposite-sex couples for their study. Men were given a clean t-shirt and told to wear it for 24 hours. They were asked not to use deodorant or other scented body products during this time and refrain from smoking and eating certain foods which might influence their scent during this time. The garments were frozen after being worn to preserve the scent.

The women were then randomly assigned to smell a t-shirt that was either unworn, worn by their partner, or one worn by a stranger, without being told which they were given. Afterwards, they underwent a stress test in the form of a mock job interview and a mental math task. Finally, they filled in a questionnaire regarding their stress levels and saliva samples were taken to measure their cortisol levels. The team asked the ladies to sniff-test the t-shirts because they tend to have a better sense of smell than men.

Overall, women who had smelled their partner’s shirt felt less stressed — both before and after the interview and math tests. Interestingly, those who both smelled their partner’s shirt and correctly identified who it belonged to, showed the lowest average cortisol levels among all the participants. This latter finding suggests that the stress-reducing benefits are most pronounced when women are also consciously aware of what they’re smelling.

“Many people wear their partner’s shirt or sleep on their partner’s side of the bed when their partner is away, but may not realize why they engage in these behaviours,” said lead author Marlise Hofer from the University of British Colombia.

“Our findings suggest that a partner’s scent alone, even without their physical presence, can be a powerful tool to help reduce stress.”

On the other hand, women who received and smelled a stranger’s scent showed higher average cortisol levels throughout all steps of the test.

The authors believe that this effect is tied to old evolutionary pressures. Hofer says that humans fear strangers from a young age, especially strange males, and it’s possible that the scent of such individuals triggers a ‘fight or flight’ response — whose observed effect is an elevated level of cortisol.

“This could happen without us being fully aware of it,” she adds.

The findings are yet to be definitive, however. The sample size is relatively small, and this study only looked at the interaction between smell and cortisol in women — who were shown to better handle stress. So more research is needed to determine whether it holds true for larger swaths of the population, and in particular, if men experience similar effects.

Still, for now, the findings offer a quick pick-me-up when your boo is out of town. But they could point the way to new stress-management strategies. For example, the team suggests packing an item of clothing that was worn by a loved one when the job takes us far away from home, to help us relax.

The paper “Olfactory cues from romantic partners and strangers influence women’s responses to stress” has been published in the Journal of Personality and Social Psychology.

Credit: British Pest Control Association, Flickr.

Bed bugs love your dirty laundry, and this has helped them travel the globe

During the mid-20th century, effective use of pesticides nearly wiped bed bugs (Cimex lectularius) from the developed world. These annoying arthropods seem to have made a comeback in the last two decades, partly enabled by cheap air travel, and partly because the parasite is very good at hopping along for the ride. Though bed bugs can’t jump or swim like flees do, one new study found the critters are at least extremely well equipped to sense human odor, which they follow … along with our dirty underwear, and eventually back into homes or hotels.

Credit: British Pest Control Association, Flickr.

Credit: British Pest Control Association, Flickr.

The bed bug isn’t much of a traveler. Instead of being on the prowl for new blood like other parasites like ticks or lice, bed bugs simply lurch in beds and other comfortable establishments which humans also incidentally enjoy. When they do come in contact with humans, they don’t stay long on our bodies. William Hentley, an entomologist at the University of Sheffield in the United Kingdom, was intrigued by this paradox: how can bed bugs be so static and ubiquitous at the same time?

Your laundry: a magnet for bed bugs

He and colleagues had a hunch the parasites were hitching rides on our luggage and laundry. To put this idea to the test, they set loose a whole swarm of bed bugs into a cell placed in the middle of a room where two cotton bags were positioned at equal distances. One was filled with clean clothes while the other was stacked with dirty socks, t-shirts, and other soiled clothing. The volunteers were very happy to oblige but I have a hunch no one wanted them back.

When the experiment was over, the researchers collected the bags and counted the number of bugs found on the surface of the clothing. They found twice as many bed bugs in the bag filled with laundry, the authors wrote in Scientific Reports. 

“There are a lot of good studies out there focused on trying to understand how bed bugs are attracted to humans and how they get around apartment blocks, but no one has really talked about how they get into the house in the first place,” Hentley told Gizmodo. “Stopping people from bringing bed bugs home can be a big step in preventing them spreading throughout the world.”

Previously, researchers found bed bugs have a good nose, being capable of sensing 100 compounds present in the human skin; odors which we spread onto our clothes.

Bed bugs don't carry disease which makes them pretty benign. In some cases, though, their bitting can cause very annoying raches or trigger alergies. Credit: Flickr, Louento.px.

Bed bugs don’t carry disease which makes them pretty benign. In some cases, though, their bitting can cause very annoying rashes or trigger allergies. Credit: Flickr, Louento.px.

Another interesting finding was related to the bugs’ carbon dioxide sensing. Some have suggested the insects sense the gas, which many living things like humans exhale, to find food. When the gas was introduced into the room, the bugs became more alert and interested in finding a meal but the presence of CO2 had little influence when it came to which of the two bags they should choose. This tells us that CO2 is indeed important and prompts the bugs to enter foraging mode, however, the gas doesn’t tell them where to find tasty blood.

On a practical level, the findings confirm that bed bugs are attracted to laundry which means you should be careful how you store them while traveling, especially when staying at a hotel or hostel. Since bed bugs can’t climb smooth surfaces, it’s better if you keep laundry on metal luggage racks. Alternatively, you could keep the dirty clothes in an airtight bag to mask the odor; your roommate might also appreciate this. Most importantly, however, never keep your luggage on the hotel bed else you risk tagging some alone with you back home.

Dogs have a higher number of olfactory receptors than humans but that doesn't necessarily mean they smell better. For instance, humans are more sensitive than dogs to amyl acetate, the main odorant in bananas. Credit: Pixabay.

Our sense of smell is just as good as rodents’ or dogs’

Dogs have a higher number of olfactory receptors than humans but that doesn't necessarily mean they smell better. For instance, humans are more sensitive than dogs to amyl acetate, the main odorant in bananas. Credit: Pixabay.

Dogs have a higher number of olfactory receptors than humans but that doesn’t necessarily mean they smell better. For instance, humans are more sensitive than dogs to amyl acetate, the main odorant in bananas. Credit: Pixabay.

Without smell, life would be dull and lame. But most people are under the impression that this is the least developed of our senses. John McGann, a neuroscientist at Rutgers University-New Brunswick, says that we shouldn’t underestimate human olfaction. The scientist recently published an extensive review of the published literature in the field so far and found no evidence that human smell is inferior to that of most mammals like rodents or dogs.

The truth about smell

According to McGann, the myth of poor human smell can be traced back to the writings of a 19th-century brain surgeon named Paul Broca who concluded the human olfactory bulb is much smaller than that of other animals. It follows that our sense of smell must be inferior too, an assertion that even influenced Sigmund Freud to say poor smell is one of the root causes that makes us susceptible to mental illness. At the same time, poor smell was seen as a hallmark of overall human superiority. It meant humans had free will since they didn’t have to rely so much on smell to survey like dogs, for instance.

“It has been a long cultural belief that in order to be a reasonable or rational person you could not be dominated by a sense of smell,” said McGann in a statement. “Smell was linked to earthly animalistic tendencies.”

Nevertheless, the idea that we smell rather poorly compared to other mammals has stuck on for ages and McGann insists it’s all a myth. For instance, McGan says the common claim that humans can only detect about 10,000 different odors is not rooted in reality. Instead, your typical human should be able to distinguish up to a trillion different odors. 

Far from nimble, the human olfactory system is comprised of a large number of neurons or at least similar in number to other mammals. Even if the olfactory bulb might be smaller than that of other mammals, proportionately speaking, there’s no evidence so far to suggest its size increases or decreases the sense of smell. Moreover, as the human brain evolved to grow larger, the olfactory bulb did not become smaller.

“We can detect and discriminate an extraordinary range of odors; we are more sensitive than rodents and dogs for some odors; we are capable of tracking odor trails; and our behavioral and affective states are influenced by our sense of smell,” McGann wrote in his paper published in Science.

“Dogs may be better than humans at discriminating the urines on a fire hydrant and humans may be better than dogs at discriminating the odors of fine wine, but few such comparisons have actual experimental support,” he added.

‘The idea that human smell is impoverished compared to other mammals is a 19th-century myth’

John P. McGann, Associate Professor of Psychology at Rutgers University.

John P. McGann, Associate Professor of Psychology at Rutgers University.

McGann cautions in his review that the myth of poor human smell is still propagated by science papers published in the 21st century, not just obscure 19th-century writings. He cites works that found rats and mice have genes that code for some 1,000 different receptors that are activated by odors while humans only have about 400. Some have seen these findings as confirmation of poor human smell. But “it has been too easy to get caught up in numbers,” says McGann, because there’s a confirmation bias even among scientists that humans have a poor sense of smell. In reality, even 400 receptors is an “awful lot”. A recent study found cows have 2,000 such genes, which is far more than both dogs and mice have but no one is claiming cows can smell splendidly.

Perpetuating this myth can even be dangerous, McGann says. Smell significantly influences our behaviour, memories, and emotions. And if some patients seem to lose their ability to detect odors, that may be a cause of concern — something which physicians should be very mindful of instead of retreating into a ‘humans smell poorly anyway’ mindset.

“Some research suggests that losing the sense of smell may be the start of memory problems and diseases like Alzheimer’s and Parkinson’s,” says McGann. “One hope is that the medical world will begin to understand the importance of smell and that losing it is a big deal.”

The smell organ as illustrated by Frank R. Paul in the June 1922 issue of Science and Invention.

Music for the nose: an olfactory organ

The smell organ as illustrated by Frank R. Paul in the June 1922 issue of Science and Invention.

The smell organ as illustrated by Frank R. Paul in the June 1922 issue of Science and Invention.

There’s a whole science behind scents. The perfume industry is worth billions and scientists all over the world, mostly in corporate laboratories, work each day to find the perfect balance between odors. In many respects, perfumery is regarded as an art of its own, and some have even drawn comparisons to music.

Dr. Septimus Piesse, a French chemist and perfumer who wrote the 1857 book The Art of Perfumery, was famous in his time for his theories that loosely compared music and how certain smells work together.

Just like an arrangement of musical notes fly together to create a spectacle for the ears, so can an array of various scents blend to enlighten the nose. Oppositely, when music goes wrong and leads to dissonance, so can some smells go horribly wrong together.

With this in mind, a 1922 issue of the magazine  Science and Invention presented a concept instrument meant for the nose, not for the ears.

The authors envisioned a “smell organ” where the artist would shoot scents instead of musical notes and dazzle his audience. The smell organ even has a whole theory behind it, as the authors envisioned  “heavier” odors assigned to lower notes, and “sharper” odors assigned to higher notes. The authors even illustrated notes that would correspond to which fragrances.

Small organ keys

The article reads:

“Of course, the combination of these odors will create a smell entirely different from any of the individual qualities of the various perfumes and it is necessary that, in the soft, dreamy compositions, the odors blend harmoniously. Discords will have a decidedly unpleasant effect but inasmuch as the composers did not dwell upon discords to any great extent, the audience will be saved the rather unusual embarrassment of smelling disagreeable combination. Some music, would perhaps have to be changed and the odors carefully graduated so that in the smells wafted over the audience no particular perfume will predominate, except when the loud pedal, or rather, in these smell organs, the strong odor pedal is trod upon.”

“It is, therefore, up to the perfumer to combine the mixtures in much the same way as an artist blends colors, or as a good florist makes up his bouquet. If it is desirable to insert a little contrast into the bouquet, the appropriate blossoms or grasses are used, and so the perfumer, likewise would have to employ the proper aromas.”

If you think a bit about it, it sounds like a brilliant idea. Imagine being in the front row of the concert hall where the olfactory organ concert is swinging away. It wouldn’t be too exciting, but if joined with images or music, preferably both, uplifting sensations might touch you.

A concert could explore the four seasons with all the odors that come with each or the story of a journey at sea told through smell. Avant-garde artists would surely throw the most peculiar odor side-shows.

Would such an instrument be possible? Well, unlike musical notes which are actually vibrations, smell doesn’t dissipate nearly as quickly. The range of emotions that one can touch over a period of time is thus very limited in the case of a smelling organ. Maybe by using an intelligent, localized venting system that can’t be felt by the audience would make such a feat possible.



ant smell

Ants can tell who’s who using their crazy sense of smell

Maybe the most amazing of social insects, ants use complex cues of pheromones to determine to which cast in the colony each individual ant belongs to. A team at University of California at Riverside found ants do this by sniffing out hydrocarbon chemicals present on their cuticles (outer shell). These cues are extremely subtle, but the ants can sense them with great sensitivity due to the way they’re hardwired. It’s enough to notice that ants have more olfactory receptor proteins in their genome than we humans have. Amazing!

ant smell

Ants communicate with each other using pheromones, sounds, and touch. Like other insects, ants perceive smells with their long, thin, and mobile antennae. Image: Fragrantica

Previously, some biologists gathered around the hypothesis that worker ants could preferentially smell only non-nestmate cuticular hydrocarbons. The hypothesis suggested that ants aren’t sensitive enough to pick up hydrocarbons from nestmates with which they share too many pheromones. Anandasankar Ray, a neuroscientist and an associate professor of entomology, wasn’t entirely convinced, though.

Him and colleagues at UC Riverside decided to go the root and study antennal neurons and their responses to hydrocarbons on the cuticle. The team individually studied the neural activity of Camponotus floridanus ants as these came in contact with hydrocarbons – long chains of hydrogen and carbon molecules. The method they used is called  electrophysiology, and involved training the ants to associate certain hydrocarbons with sugary water, then measuring the electrical response of the neurons to these reactions. To their surprise, the researchers found the ants could distinguish between various forms of hydrocarbons with extreme sensitivity.

“These guys can smell almost any hydrocarbon we offered to them,” Ray said for Washington Post. “Along with it, we also discovered not only did they have a very extensive olfactory system, they are also able to distinguish very well between very closely related [compounds]. They are able to tell the difference between a hydrocarbon with 25 carbon atoms versus 24 atoms.”

“This broad-spectrum ability to detect hydrocarbons by the ant antenna is unusual and likely a special property of social insects. Using this high-definition ability to smell ‘ant body odor’ the ants can recognize the various castes in the colony as well as intruders,” Ray added.

When you go deeper into this, it starts making sense too. Hydrocarbons are low volatility compounds, meaning you have to be very close to them to pick them up, even if you’re a super sniffer like an ant. If they had gotten their cues from some different compound, say much more volatile, it would have been impossible for the ants to distinguish one another. A language becomes powerful when it is complex and meaning can be conveyed as specifically as possible. That’s what words are for. For ants, their language is chemical and cues have to be very subtle.

The broad-spectrum sensitivity of Camponotus laevigatus allows these ants to detect CHCs from both nestmates and non-nestmates.  Image: Cell Reports

The broad-spectrum sensitivity of Camponotus laevigatus allows these ants to detect CHCs from both nestmates and non-nestmates. Image: Cell Reports

Ultimately, depending on the cast it belongs to (queen, worker, warrior), each ant has its own blend made up of several cuticular hydrocarbons, the authors write in Cell Reports.

“We are closing in to finding the functional roles of these receptors, and, in particular, finding the olfactory receptors that detect pheromones from the queen who regulates much of the order in the colony,” Ray says.

Comet 67P/Churyumov-Gerasimenko. Credit: AFP/ESA/Rosetta/MPS

Comets stink: space probe finds odor of urine, rotten eggs and alcohol

Ever wondered how a comet smells? Well even if you could, you might wish you hadn’t: rotten eggs, horse pee, alcohol and bitter almonds are just a couple of the fragrances you could sniff.

A smelly comet

Comet 67P/Churyumov-Gerasimenko. Credit: AFP/ESA/Rosetta/MPS

Comet 67P/Churyumov-Gerasimenko. Credit: AFP/ESA/Rosetta/MPS

These volatile compounds were detected by  a mass spectrometer aboard the Rosetta probe which is currently studying the Comet 67P/Churyumov-Gerasimenko. The mass spectrometer analyzed the chemical signature of  gas given off by the “coma,” the comet’s head, and found numerous unexpected compounds. The Rosina team believed only the most volatile molecules — carbon dioxide and carbon monoxide — would be released as the comet’s icy surface started slowly to warm, but they were in for a surprise.

“The perfume of 67P/C-G is quite strong, with the odour of rotten eggs (hydrogen sulphide), horse stable (ammonia) and the pungent, suffocating odour of formaldehyde,” said Kathrin Altwegg, Rosina’s chief scientist.

“This is mixed with the faint, bitter, almond-like aroma of hydrogen cyanide.

“Add some whiff of alcohol (methanol) to this mixutre, paired with the vinegar-like aroma of sulphur dioxide and a hint of the sweet aromatic scent of carbon disulphide, and you arrive at the ‘perfume’ of our comet.”

Project leader Kathrin Altwegg of the University of Bern said the aroma will get stronger as 67P gets closer to the sun, causing it to release more gas and form the coma characteristic of comets. On August 13 next year, the comet and Rosetta will be 185 million kilometres from the Sun, their closest approach to our star.

Comets from another solar system

Image: Telegraph

In other comet-related news, astronomers have identified over 500 exocomets – comets swarming through solar systems other than our own. The discovery was made after more than  1,000 separate observations were programmed between the years of 2003 and 2011 through the HARPS instrument, which is a part of the ESO 3.6-meter telescope at the La Silla Observatory in Chile.

Flavein Kiefer, research team leader, says “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”


The human nose can distinguish over a trillion scents


A volunteer smelling a vial. Photo: Credit: Zach Veilleux / The Rockefeller University

There’s a common number thrown around for how many scents a human can smell – 10,000. Even scientific literature has cited this figure, though it is highly debatable. This makes a lot of people believe that they have an extremely poor sense of smell compared to most animals, like familiar canines. In reality, it seems humans may be able to smell more than one trillion different odors, debunking the myth that we humans have a nose only for a fraction of the molecules out there.

[ALSO READ] The uniqueness of smell: no two people smell the same

There’s a reason we can smell. It’s a fundamental sense that helps us distinguish between what foods are right to eat or not, sense danger and even find mates. There’s a sort of inferiority complex regarding our sense of smell. Ask most people on the street how they think their sense of smell is compared to animals, and they’ll tell you that we can smell oh so little. That may not be true, according to researchers at Rockefeller University in New York.

Going with your nose

The typical nose has 400 or so olfactory receptors, but that doesn’t mean they only bind to 400 molecules. Rather, these receptors work together to sense various mixes of molecules. For instance, the eye has only three eye receptors (the cones), yet people can see up to 10 million colours. It’s hard to distinguish a colour from another very similar one, but even though the nuances may by very subtle, your brain can still pick them up.

For the experiment, mixtures of 128 different scent molecules were created. Individually, the molecules resembled odors such as grass or citrus, but when they were all combined, the mix smelled unfamiliar. The team led by Leslie Vosshall, an olfaction researcher at the Rockefeller University in New York, asked volunteers to smell three vials containing three scents (two of one scent along with a third, different scent) and identify which of the three was unique. This process was repeated for more than 260 sets of vials.

[RELATED] Psychopats can be spotted through a smell test, study says

Based on how often the volunteers were able to identify the correct unique smell, an extrapolation was made to estimate how many scents an average person could distinguish out of all possible mixtures of 128 molecules. Their calculations suggests that an average person can distinguish from up to 1 trillion scents, but this figure could be much higher because there are more than 128 odor molecules.

Of course each person smells more or less better. The keenest sense of smell, based on previous research, is that of a non-smoking caucasion woman, in general.

Findings appeared in the journal Science.


Why winter smells different


People living in areas with distinct seasons will often say — “smells like winter outside”. It’s that distinct odor in the air, which most of us can’t quite grasp and describe into words. What makes winter smell the way it does, though? What differentiates it from other seasons, say summer, isn’t some new kind of smell in the atmosphere that comes with the season, but rather the perception comes as a result of your nose getting desensitized.

When it’s cold outside, the olfactory receptors that lie deep inside the nose – onto which odor molecules attach causing an electrical signal to be sent to the brain which we process into smell – nestle themselves deeper in the nose, as a protective response against low temperatures that might hurt them. This makes it harder for odor molecules to cling and, consequently, affects your smell.

Also, suspended molecules travel faster through the atmosphere with rising temperatures. During the cold winter, molecules are slower, which might explain why you’re bombarded by some many smells during summer time or why some particular odors are so intense (garbage day, yuck!) during scorching hot days. The same reasoning applies to food as well. Think of the smell of a hot soup versus a cold one.

Of course, there’s the undeniable psychological component, that need not be neglected. Most often than not, what we expect to smell is what we actually smell, even though that specific perception shouldn’t naturally occur.

“What you think a smell will be impacts whether you like it and what you perceive it to be,” said Alan Hirsch, a neurologist and psychiatrist in Chicago for Discovery. “So, if you go outside in the winter and you are used to smelling snow or chestnuts in the fire or whatever you happen to smell outside, that’s what you will interpret smells to be.”


The uniqueness of smell: no two people smell the same


Photo credit: psychologies.co.uk –

Just like taste, it’s really common for people not to agree on how pleasant or fowl a scent may be. You might find the meal you just cooked to have a pleasant odor or you might have bought a perfume you thought smelled divine, only for some other person to disagree and express a distaste. Apparently, according to researchers at Duke University, no two people have the exact sense of smell, meaning the way you perceive the odors around you is unique.

That’s not to say, of course, that everybody has a dramatically different perception over smell – most common smells are easily recognizable and perceived more or less similarly. It’s those subtle variations, which in some cases lead to opposite standing contradictions, that cause uniqueness.

[ALSO READ] White smell: the neutral fragrance discovered by scientists 

The way you smell, like any other biological functions, is governed by your genes. Humans can distinguish more than 10,000 different smells (odorants), which are detected by specialized olfactory receptor neurons lining the nose.  Some  400 genes have been discovered so far coding the receptors in our noses, and according to the 1000 Genomes Project, there are more than 900,000 variations of those genes. When a odor (molecule) binds to these receptors, a specific signal is sent to the brain, processed and retrieved as smell.

The missense of smell

According to Hiroaki Matsunami, Ph.D., associate professor of molecular genetics and microbiology at the Duke University School of Medicine, the receptors in any two people should be 30% different.  What this means is that people actually perceive smell quite differently, judging from this figure. Also, promoter regions of the genes, which are highly variable, or gene copy number variation, which is very high in odor receptors, weren’t taken into account so actually 30% is a conservative appreciation.

“There are many cases when you say you like the way something smells and other people don’t. That’s very common,” Matsunami said. But what the researchers found is that no two people smell things the same way. “We found that individuals can be very different at the receptor levels, meaning that when we smell something, the receptors that are activated can be very different (from one person to the next) depending on your genome.”

Previously, scientists discovered the genes that encode the smell receptors, however it was rather unclear how these receptors worked in response to odors. Mastunami and colleagues cloned more than 500 receptors each from 20 people that had slight variations of only one or two amino acids (the smallest difference in DNA), then systematically exposed these to various chemicals to see how these bonded to the receptors.

The various odorants, like vanillin or guaiacol, were released in incremental concentrations – 1, 10 and 100 micromoles –  and in doing so, the researchers identified 27 receptors that had a significant response to at least one odorant.

The findings, reported in a paper published in Nature Neuroscience, could influence the  flavors, fragrance, and food industries.

“These manufacturers all want to know a rational way to produce new chemicals of interest, whether it’s a new perfume or new-flavored ingredient, and right now there’s no scientific basis for doing that,” he said. “To do that, we need to know which receptors are being activated by certain chemicals and the consequences of those activations in terms of how we feel and smell.”