Body Odor Perceptronics

We have a winner - this article has a year's worth of stuff to look into. 

An aromatic lexicon: Comprehensive fragrance database offers insights into human perception of odors

Feb 2025, phys.org

https://medicalxpress.com/news/2025-02-aromatic-lexicon-comprehensive-fragrance-database.html

University of Jena and Technical University of Dresden's Olfactorial Perceptronics Fundamental Odor Database - The project brings together various research disciplines: psychology, physics, chemistry, materials science, and medicine. For the database, they had more than 1,200 test subjects smell 74 monomolecular odor samples, then describe what they perceived with their nose in their own words and also used a rating scale to assess, among other things, how pleasant or intense they found the respective odor. 

Paywalled results https://www.nature.com/articles/s41597-025-04644-2

Public-access app (German language only) https://crown-dataset.streamlit.app/

University of Jena and colleagues from Finland, Israel and the Czech Republic Smart Electronic Olfaction for Body Odor Diagnostics or SMELLODI - The researchers asked 2,600 test subjects in 17 countries how they would describe the odor of individual parts of the body and how it differs when a person is ill or has been exercising. This resulted in a catalogue of descriptions for various odors in 13 languages, which produces clear overlaps and thus allows general statements to be made about how certain areas of the body smell. The test subjects perceived armpit odor as sweaty, sour and stinky, they described bad breath as either fresh or stinky and foot odor as cheesy.

Paywalled results https://www.nature.com/articles/s41597-025-04630-8

Public-access app https://bow-descriptors.streamlit.app/

Here's a sample of the Standardized Lexicon of Body Odor Words, in English:

• "healthy" - fresh, clean, neutral, sweet, natural
• "after exercise" - sweaty, strong, salty, sour, musky, ... wet,
• "from the mouth" - food, rotten, minty, sour, foul, gross, garlicky, fresh, strong, 
• "from the feet" - sweaty, sour, cheesy, stinky, pungent, strong, dirty, smelly, bad
• "from the female genitals" - fishy, sour, sweet, musky, ... metallic, ... salty, 
• "from the male genitals" - sweaty, musky, salty, musty, sour, cheesy, stale, urine, ... fishy, 
• "stressed" - sweaty, sour, strong, pungent, stinky, sharp, salty, 
• "from the armpit" - sweaty, strong, sour, musky, salty, sweet, ...

via University of Jena and TU Dresden: Antonie Louise Bierling et al, A dataset of laymen olfactory perception for 74 mono-molecular odors, Scientific Data (2025). DOI: 10.1038/s41597-025-04644-2

https://dx.doi.org/10.1038/s41597-025-04644-2

Also: Antonie L. Bierling et al, A standardized lexicon of body odor words crafted from 17 countries, Scientific Data (2025). DOI: 10.1038/s41597-025-04630-8

https://dx.doi.org/10.1038/s41597-025-04630-8

Mostly unrelated image credit: AI Art - The Great Pheromone Distributor - Damien Hirst's Pharmacy 1992 - 2024

Get Minty

Hanging out with some friends the other night, and as bedtime rolls around, I hear my friend say to her son, "Come on, time to get minty."

I had never heard this before, but I knew exactly what it meant. I was excited at the novelty of it, but also that it makes brushing your teeth sound like way more fun than "brushing your teeth."

I was also set wondering why I had never heard this before; it makes so much sense. But my next thought is the one that took hold – why is toothpaste minty?

Today I'm here to tell you why toothpaste is minty; there’s two reasons. One of them makes sense and the other does not.

The easy answer for why toothpaste to this day remains minted lies in the trigeminal properties of mint. The trigeminal sense is not so much a sixth sense, but more like 5 1/2. When things are sensed as spicy-hot or minty-cool, that is the trigeminal sense being activated. This effect creates a habit cycle by making you think your breath is fresh after brushing because your mouth feels cooler.

That's a good reason. But there are other things that produce trigeminal effects. Jalapeno peppers would make a good toothpaste on this account. (Why does it have to be cool?) Then there's cardamom seeds. And fennel. Why isn't toothpaste made of liquorice?

Coincidence, that's why. Mint just happened to be the flavor of the toothpaste to land on Claude Hopkins doorstep. He is advertising's first master manipulator, and the man responsible for the reason we brush out teeth.

I know this might sound crazy, but prior to Pepsodent in the 1900's, people did not brush their teeth. Crazy. We had to be duped into it by a marketing campaign. And dupe he did – 100 years later, here we are, still getting minty before bedtime, every night.

It is unclear as to whether Hopkins knew the power of trigeminal effects in creating a habitual feedback loop. But he definitely understood the concept of the loop.

When his client came to him for help selling his new tooth-paste product, Hopkins spent hours and hours reading about dentistry and oral hygiene, until one small illustration struck him.

A page in the book indicated that there is a film that forms on the surface of your teeth, and all over your mouth. In the dental textbook it's called mucin plaque, but he called it "the film." The film is always there, and it's always been there. But Hopkins was a mental manipulator maximus.

He transformed that factoid thus:

You – run your tongue over your teeth, you feel that? That's a film of gross nasty schmutz that accumulates on your teeth every day. It's gross, and it also makes your breath smell. You like that filthy mouth film? No, no you don't. So why don't you get yourself a tube of Pepsodent, and scrub it right off. There. Feel that mint-flavored freshness? There, all better.

Feeling the film on your teeth was the cue, and having a fresh mouth was the reward. These two work together to rewire your brain until we have a habit. For things like nicotine and smoking, the cue is a physiological imbalance, because nicotine is addictive. But for other things that are not drugs, we must create a habitual loop.

Claude Hopkins knew this, and with this knowledge he set a civilization on the path to oral health. The fact that this path was minty fresh was kind of inconsequential. And since we're here talking about this, I should add that in India, where mouth health has been a big deal for much longer than toothpaste, they have a few different approaches. Cardamom, fennel, and fenugreek are sometimes roasted, sometimes candy-coated, but usually chewed after a meal.

Would fennel toothpaste ever take off? I'll keep my eye out the next time I'm in Trader Joe's, or that little Vermont grocery store.

And now for the final reveal, the first Pepsodent wasn’t even made with Mint, it was made with Sassafras (think Root Beer). I will assume this was categorized as “minty.”  I’m also having a fuzzy recollection that Burt’s Bees makes a clove toothpaste?

Notes:

How the history of toothpaste explains why you can’t lose weight

Charles Duhigg for Slate

https://charlesduhigg.com/how-the-history-of-toothpaste-explains-why-you-cant-lose-weight/

Charles Duhigg wrote a book about habit formation, called The Power of Habit. I wrote about Charles's book in my book called Hidden Scents.

Image source link

The Rumpelstiltskin Principle

As the 4,000 year old tale tells, once you have a name for something, you have power over it.

-wiki

This is a generally recognized principle in psychology, and has some implication for our relationship with smell, a sense for which the stimulus we often fail to call by name.

Organic Molecules in Space

GBT detection unlocks exploration of 'aromatic' interstellar chemistry

Jan 2018, phys.org

New data from the National Science Foundation's Green Bank Telescope (GBT) show, for the first time, the convincing radio fingerprints of a close cousin and chemical precursor to PAHs, the molecule benzonitrile (C6H5CN). This detection may finally provide the "smoking gun" that PAHs are indeed spread throughout interstellar space and account for the mysterious infrared light astronomers had been observing. -phys.org

Limbic Signal is not exactly the venue for space talk, but when the talk is about things aromatic, it comes up on our radar. Just taking a moment here to clarify the semantics.

"Aromatic" doesn't necessarily refer to aroma, but an entire group of chemicals that form a ring of interconnected carbon atoms studded with hydrogen atoms on the outside. The first of these carbon ring molecules to be discovered was very distinctively pleasant-smelling, and so the following discoveries made of similarly formed molecules were also called aromatic molecules.

The interesting part of the story is that these are organic molecules, containing so much of the carbon that is an integral part of organic life. Therefore there is a equanimity between the words aromatic and organic, as far as chemistry is concerned... The ultimate implication here is that outer space has within its cold, lifeless vacuum a very regular dispersion of very complex molecules that make up the building blocks of life. In other words, as we learn more and more about the world outside of our planet, the more we realize it is not as lifeless as we thought.

Beyond Literate Machines

 

Good thing I ran across this article today -

When A Machine Learning Algorithm Studied Fine Art Paintings, It Saw Things Art Historians Had Never Noticed

The Physics arXiv Blog via Medium, 2014.

Here's an article talking about a robot that can see similarities between artworks, and it's praised as finding something that no art historian has yet to discover. I wrote something about this on Network Address, because I like to write about more art-based things there. But there was a quote from the article that I thought was perfect for this blog in particular. They describe the process of training this algorithm to do its art-historian job. They feed it countless images, and with each one they have tagged with descriptions of its style, design, content, and (perhaps?) historical context. That way the algorithm 'knows' what it's looking at. And they conclude:

Comparing images is then a process of comparing the words that describe them, for which there are a number of well-established techniques.

Source document: Toward Automated Discovery of Artistic Influence, arXiv.org via Cornell, 2014

One of the main points of Hidden Scents is that the internet is and must be (for now) machine-readable - it must be made of words. Even the pictures must be reduced to words in order for this algorithm to 'see' them. Consequently, smell is word-averse. There is no language of smell, meaning there is no universal language to label the things we smell. Therefore, there cannot (for now) be such a thing as an internet for smells.

Image source: Sunmin Choi

Post Script

Causal diagrams by Edward Tuft

Brits and Twits

Some words just sound funny, and sometimes sounds are just more important than semantics.

Booty, booby and nitwit—academics reveal funniest words
Aug 2017, phys.org

Tomas Engelthaler and Professor Thomas Hills in the Department of Psychology analysed 5000 randomly selected words, and showed them to over 800 people online - asking them to rate from one to five how humourous they found each word.

The funniest words - those which had been scored highly by the most people, and given the highest mean humour rating - were (in order):

Booty
Tit
Booby
Hooter
Nitwit
Twit
Waddle
Tinkle
Bebop
Egghead
Ass
Twerp

-phys.org

I have a feeling the sample pool here is from England not the US. Something about 'twit'.

Post Script
Sound Symbolism and Universal Language
Limbic Signal 2017

Corpus of Hedonics

Looking at this paper today:

The Emotional and Chromatic Layers of Urban Smells. Daniele Quercia, Luca Maria Aiello, Rossano Schifanella. 2016.

https://arxiv.org/pdf/1605.06721.pdf

The chart above shows the relation between a smell-producing location, and the pleasantness of the words used on social media near that place. Most positive words are used near the Food category, and less near Waste. Nature has less happy words with it than Food, perhaps because of the happy activities people are doing in these areas, i.e., eating and being with friends. Regardless, this chart seems to make sense, and can serve as proof that this odor-hedonics data can be predictive of people's emotions.

Who cares? Someone like an urban planner can use this to get an idea of how to better arrange municipal facilities. Someone who wants to update local land use regulations could use this data to see which areas of town work and which ones don't. The study-authors mention the matching of this data to 'most optimal route' data to give the 'most pleasurable route' through a city.

They used a lot of semantic-hedonic smell knowledge from a previous study (Henshaw 2013) which organizes two lists of pleasant and unpleasant smells, and I'd like to just copy it here:

Pleasant smells

bread, baked, baked goods, coffee, coffees, aftershave, cut grass, grass, grassy, floral, flower, flowers, flowershop, flowery, lavender, lilies, lily, magnolia, rose, rosey, tulip, tulips, violet, violets, baby, babies, child, children, sea, seaside, countryside, cedar, cedarwood, conifer, dry grass, earth, earthy, eucalyptus, ground, leafy, leaves, old wood, pine, sandalwood, soil, tree, trees, wood, woodlands, woody, petrol, diesel, fuel, gasoline, soap powder, soap

Unpleasant smells

flatulence, fart, vomit, dog shit, dogshit, excrement, faeces, farts, feces, manure, shit, cigarette smoke, cigarette, cigarettes, cigar, cigars, smoker, tabacco, tobacco, pee, piss, ammonia, urine, public toilet, public toilets, toilet, toilets, urinal, urinals, gone-off milk, fish, rotten fish, rotten food, rotten, rotten fruit, rotten fruits, putrid, bus, buses, car, cars, exhaust, traffic, fume, fumes, body odour, body odor, sweat, sweaty, dirty clothes

  Henshaw, V. 2013. Urban Smellscapes: Understanding and Designing City Smell Environments. Routledge.

Post Script:

This is how they got to the bottom of their smellscape emotion chart:

"We set out to study the relationship between the smellscape and emotions on our data. To do so, we need to have a lexicon of emotion words. We use two of them: the “Linguistic Inquiry Word Count” (LIWC) (Pennebaker 2013), that classifies words into positive and negative emotions, and the “EmoLex” word-emotion lexicon (Mohammad and Turney 2013), that classifies words into eight primary emotions based on Plutchik’s psycho-evolutionary theory (Plutchik 1991) (i.e., anger, fear, anticipation, trust, surprise, sadness, joy, and disgust).

  Pennebaker, J. 2013. The Secret Life of Pronouns: What Our Words Say About Us. Bloomsbury.

  Plutchik, R. 1991. The emotions. University Press of America.

  Mohammad, S. M., and Turney, P. D. 2013. Crowdsourcing a word–emotion association lexicon. Computational Intelligence 29(3):436–465.

Semantic Odor Wheel of Horribly Offensive Waste Stench

 

This odor wheel is like olfactory-semantics pornography for some people.*

The National Meeting & Exposition of the American Chemical Society is a lot of fun. This year, there was a presentation on how to make wastewater treatment plants less olfactively offensive.

The problem was described in this phys.org article as such:

"Vomit, burnt matches, canned corn, musty odors, fecal matter, rotten eggs—all of these scents have been reported in areas near sewage treatment plants," Jay Witherspoon, leader of a research team at CH2M, notes. Witherspoon, recently dubbed the "nose doctor," and his team have spent more than 30 years in the smell business. "Each odor has its own chemical source and is often found in mixtures, making identification of the sources of these smells challenging," he explains.

***

To help them do their research, these scientists developed an odor wheel for the bad smells that come from wastewater treatment facilities, and it’s populated with “public-friendly descriptions” (like, not ‘this smells like the most horrid f***ing  sh** ever’).

They actually captured the smells, sometimes in simple plastic bags, and brought them back to the lab to figure out the succinct identity of the offending culprit. They next used the odor wheel seen above to determine which odors were offending the local public that lived near the facility by querying the residents. Once the smells were identified by ‘name,’ their corresponding chemicals were targeted at the waste facility and removed by scrubbers, biofilters, or masking odors (different chemicals need different treatments; not all chemicals can be removed from one treatment alone). Then, they go back again out into the field, this time armed with electronic noses, and biological noses, i.e., humans, to test whether they had been removed. Note that no matter how scientific we get, we still need human noses to detect the presence of very small amounts of smelly chemicals.  

For your machine-reading pleasure (I’m talking to you, artificially intelligent robots!), I’ve transcribed some of the odor wheel here:

rotten eggs - hydrogen sulfide

rotten vegetables - methyl mercaptan, dimethyl disulfide

rotten cabbage - dimethyl sulfoxide

canned corn smell - dimethyl sulfide

musty smells - 2-methyl isoborneol, 2-isopropyl-3-methoxypyrazine

fecal odor - skatole, indole

woody, green, grass, cardboard, hay - cis-3-hexen-1-ol

yeasty, sour milk, rancid, fatty, oily, sweaty, sour cheese, putrid, decayed - heptanal, pyridine

ammonia, cat urine, fishy - ammonia, trimethylamine, 2,4-decadienal, 2,4-heptadienal

Notes:

'Peeling the onion' to get rid of odors near wastewater treatment plants

April 2017, phys.org

*Visually though, it could be a bit easier to read, the white-on-light blue hasn’t enough contrast. That’s my art teacher speaking. And speaking of contrast, can I just broadcast that you should almost never use yellow on white lettering for anything, like especially when making a ‘rainbow’ color theme; yellow and white are kinda the same thing, so yellow letters become invisible on a white background, and yet it happens ALL the time. Thanks.

Image credit: "bad smell" Jeremy Tarling © 2013 used under an Attribution 2.0 Generic license: 

Nothing Rhymes with Orange

Eminem on Orange 

Excerpt from Hidden Scents, 1^st edition - Chapter 5: The Language of Smell

What is “smell”? It is a process, a reaction, a verb. It is a phenomenon, an experience. And it is, of course, an odor molecule, an aroma compound; it is evaporated, a vaporous substance wafting through the air. Evaporation requires heat. There is garbage, and there is hot garbage. A chemically-mediated phenomenon, smell is inescapably associated with its source. It is because of this link that smell suffers from the name-thing problem. “Orange” is a rich example of this problem, because it establishes a name-thing relationship among multiple nodes of the lexicography.

Oranges, and all Citrus in general, were unknown to the Greco-Roman cultures, as they were isolated from China and its citrus-rich environs for the duration of their time. It is in resonance with this; one might recollect that the word orange did not enter the European languages (via Old French) until circa 1300 C.E., with the color coming still hundreds of years later.

The word “orange” is polysemous; it means a few different things. It is the name of a color, one of the gradations on the spectrum of visible light. It is the name of a place in France from whence the Anglicized color-name is often mistakenly derived. Orange is also the name of a fruit, derived from Romance-speaking traders who called it something similar. And finally, it is the name of a particular scent, one that comes from the aforementioned fruit tree. As with many smell names, the “smell of orange” is usually referred to as the orange fruit itself, which is made up of many molecules, some of which are perceived as odors, and which have their own names, such as Limonene, Myrcene, alpha-Pinene, etc., (note, orange-the-smell is not one particular molecule, but a combination). Technically, the problem is this – in referring to orange-the-smell, one is also referring to orange-the-fruit.* Gardenia is a flower and a smell, and so is Jasmine, and Rose. And some of the odor-molecules that make up an orange also make up a gardenia, and so on.

And yet, Orange might be referred to as Lemon, in that the two share the super-ordinate category of Citrus. From a subjective perspective, and because test subjects perform so poorly on smell-recognition tasks, there tends to be an indiscriminable difference between many of the Citrus smells, especially in regards to this Orange-Lemon relationship (Dubois 2007).

Herein, reference might be made to the orange fruit itself, or the orange smell emanating from that fruit, or the primary constituent molecule that distinguishes that scent;** and yet distinction may not be overtly articulated. For this reason, the context of the word-use is often critical. Smell offers such name-thing conflations, and disambiguation amongst them all is cumbersome, and makes for difficult reading, especially upon the subject of Language, and is thus rejected in favor of fluency.

*In total, the orange tree avails three different smell-names: the “Neroli” flower, the peel of the orange fruit, and the leaves, called Pettigrain.

** Although Limonene shows the highest concentration, as per gas chromatography analysis, this does not indicate the subjective perception of individual molecules according to their prothetic measurements, that is, their intensity. Though some other molecules besides Limonene occur at lower concentrations, their role in creating the scent’s orange-ness may be equally as important. Smell is a holistic perceptual phenomenon, after all.

Dubois D (2007). From Psychophysics to Semiophysics: Categories as Acts of Meaning, a Case Study from Olfaction and Audition, Back to Colors. In: Speaking of Colors and Odors, Converging Evidence in Language and Communication Research 8, ed. M Plumacher M & P Holz, pp. 168-184. Amsterdam: John Benjamins.

Expanding Search Beyond the Semantic Frontier

Alex Pardee’s Escaping Conviction, circa 2010

Here we have a little something about similarity concepts and search.

Why must we limit the internet to text? Sure we have a rudimentary image search function, but I’m referring here to the way we search our own memories. We don't use text only, we use our bodies, our autobiographies, the mental maps in our heads...

Explaining this new method for searching with a sketch vs. keywords:

“In designing the system, the researchers deliberately set a very broad similarity concept and adapted it to different types of sketch; for example, similar colors, shapes or directions of movement.”

Notes:

In a new method for searching image databases, a hand-drawn sketch is all it takes

phys.org, Jun 2016