Wednesday, November 30, 2016

The Smell Monster

 AKA Isonitriles
AKA The Godzilla of Smells

First, here’s some common bad smells, taken from an entry on Stink Bombs

Hydrogen sulfide, smelling of rotten eggs
Ammonium sulfide, rotten eggs
Propionic acid, sweat
Butyric acid, rancid dairy
Caproic acid, smelling of cheese
Ethylamine, fishy smell
Putrescine, rotten meat
Cadaverine, rotten meat
Skatole, smelling of feces

Smells can instigate a physical response like no other sense. The sight of a disinterred body might reflex your neck, but it’s the molecules that make you lose your lunch, not the photons. There is debate about what is the worst smelling thing, and it’s one that can never be resolved, because people simply don’t smell things the same.

Because they are so context-based, smells can change drastically from person to person. Perhaps the best example of this is isovaleric acid, which smells like both vomit and Parmesan cheese. Isovaleric acid is called delicious by half the people smelling it, and disgusting by the other half. (This depends on the study group; I believe this is an aged-cheese-eating, western-culture-biased pattern that would change for kimchee eating cultures, or sauerkraut, or Durian fruit.) But the point is that the response is fifty-fifty, and there’s no way of telling which will come up.

And just think of the obvious – people don’t mind their own body odors as much as they do those of others, even though they are, for the most part, made of the same molecules.

Speaking of non-lethal weapons, the military uses bad smells for things like riot control. You’ve got the U. S. Government Standard Bathroom Malodor bomb, which smells like a filthy outhouse, and the Who-Me, which you would think smells like farts, but is described as rotting flesh.

It’s important here to recognize that these are the best odor cocktails they could come up with, but they are not absolute; they will not work for everyone. If someone were to have a specific anosmia to the major constituent molecule of this military stink bomb, it would be powerless to them. (And half the population has odor-blindness to at least one of the sixty known anosmias, most of which are “bad” smells.)

This is where the isonitriles come in. I imagine they are not used in non-lethal weaponry because they are in fact toxic. And they have a reputation for being the worst smelling thing ever, but not exactly for the reasons you might expect. They mess with your mind just as much as your nose.

Let me first drop a description from a working chemist:
The smell is indescribable. Not that it is so ungodly beyond all expected levels of stink, which it approaches, but more it is like nothing you have ever experienced and your brain while certainly repulsed to the extreme, struggles to define it. A double assault at your senses. It has a persistent linger on everything that comes near it including your neurons. Much like a horrible picture you see that can’t be purged from your mind. Even after the scene changes you are left with a ghost difficult to eradicate. While HCL + alcohol cleans off hard surfaces well, it does nothing for your memory.

And a more full-bodied description:
Witnesses to the stench claim words cannot describe it. But after reading many firsthand accounts of their ordeals, one begins to piece together a dim picture of the odor as a sort of beast that takes the whole sensory apparatus hostage, leaving victims feeling abused and violated. Like a brutal tyrant, it seems, the smell makes itself felt even after one leaves its immediate presence.

I find it very interesting that this description relates so much to the White Smell discovery that won a nobel prize relatively recently. It is also a smell that cannot be described. It doesn’t smell like anything, yet you know it when you smell it. The way it works is you level all the intesities of the smells in the mixture until they just cancel each other out. Grapefruit is nice at low doses, but can make you gag in higher concentrations. You would adjust the concentration of it, and the others in the mixture, until all the smells are technically invisible.

I just can’t help but to add this descriptor from an article on Selenophenol, (not the same thing as an isonitrile, just another bad smell).

“Organoselenium smells like a robot farted.”

U. S. Government Standard Bathroom Malodor bomb:

62.82% Dipropylene glycol
21.18% Thioglycolic acid
6.00% Hexanoic acid
6.00% N-methyl morpholine
2.18% p-cresyl isovalerate
0.91% 2-naphthalenethiol
0.91% Skatole

D. Hank Ellison, CRC Press 2008, 2nd ed.

Wednesday, November 23, 2016

At the Cutting Edge of Olfaction

This is a really cool book on the state of the art as well as the future of artificial olfaction.

Human Olfactory Displays and Interfaces: Odor Sensing and Presentation
Takamichi Nakamoto (Tokyo Institute of Technology, Japan). 2013. 555 pages. direct link

Although good devices exist for presenting visual and auditory sensations, there has yet to be a device for presenting olfactory stimulus. Nevertheless, the area for smell presentation continues to evolve and smell presentation in multimedia is not unlikely in the future.

Human Olfactory Displays and Interfaces: Odor Sensing and Presentation provides the opportunity to learn about olfactory displays and its odor reproduction. Covering the fundamental and latest research of sensors and sensing systems as well as presentation technique, this book is vital for researchers, students, and practitioners gaining knowledge in the fields of consumer electronics, communications, virtual realities, electronic instruments, and more.

[From the Foreword, by Jiri Janata]
Olfaction and taste are two truly chemical senses in which the interaction of the molecule and/or group of molecules with olfactory receptors triggers a chain of complex physiological events, which end in a cognitively interpreted “sensation.” In humans, such sensation can be articulated and can lead to various descriptions that can be anything from general, e.g. “pleasant/unpleasant,” to highly specific, such as chlorine, ammonia, or cinnamon. For most vertebrates, smell is existentially important because it predefines actions as diverse as “to run” or “to mate.” It could be argued that some animals are biological machines whose sole purpose in life is to reproduce and olfaction is one of the key enabling functions.

For many years, engineers and scientists have been fascinated with the idea of explaining olfaction and constructing artificial olfactory machines that do just that. Thus, biology has once more inspired creative activity that has resulted in hundreds of worthwhile and also some questionable publications. It has even received recognition at the Nobel Prize level. The present book belongs to this enormously fertile, but complex area of scientific endeavor.

[From the Preface, by Takamichi Nakamoto]
Although a human interface for vision and audio has been already been developed, an olfactory interface has not. However, people are becoming interested in olfaction as the next-generation human interface. A human interface for olfaction is composed of an olfactory display and an odor sensing system called an electronic nose. An olfactory display is an output of a machine, whereas the odor sensing system is its input. These are important to realize a human olfactory interface. Since an odor sensing system has been studied for last two decades, the researcher population is relatively large. An international conference of machine olfaction is held every two years. However, there are not many olfactory-display researchers, since the olfactory display only recently evolved in virtual reality. Although both fields have been studied separately, it is indispensable to see and understand both the olfactory display and the odor sensing system for developing human olfactory interfaces and their applications.

Saturday, November 19, 2016

Post-Truth is the Word of the Year

Truthiness, etc. In other words, The Age of Approximation is upon us. Read about it in Hidden Scents: The Language of Smell in the Age of Approximation

Let’s hear about it, from the BBC article:
“It is defined as an adjective relating to circumstances in which objective facts are less influential in shaping public opinion than emotional appeals.

“Mr Grathwohl said: "Fuelled by the rise of social media as a news source and a growing distrust of facts offered up by the establishment, post-truth as a concept has been finding its linguistic footing for some time," he said.

“Its frequency of its usage increased by 2,000% in 2016 compared with last year.”

Friday, November 18, 2016

The Next Generation

The next generation of artificial intelligence is here; we’re teaching robots how to think like humans more and more each day. You might not call them robots, but instead artificial intelligence programs tasked with simple operations like visual recognition or speech recognition. They are different from conventional AI programs in that they learn how to do things instead of being told what to do. So, in short, these programs are a lot more like humans in that they have a new way of “learning,” and it happens to be a lot like the way our nose-brain makes sense of the world.

This new AI approach is called, in shorthand, ‘neural networks’ or ‘deep learning.’ Our sense of smell works a lot like a neural network, putting together various layers of recognition, until entire episodes of experience are encoded or released.

These neural networks have been coming up in the news quite often as of late, so I thought I’d re-post some of the good explanations and examples, all of which come by way of Google Labs and Wired magazine. If you’re interested in these things, check out some of Hidden Scents, as it comes around to the concept of neural networks quite often.

Wired writer Margaret Rhodes writes a piece for those wondering "what the f*@k neural networks are and how they work," but she also links us to Daniel Smilkov, a member of Google’s Big Picture Research Group, and Shan Carter, who creates interactive graphics for The New York Times, who both wanted to teach people what these things really are. Play with their amazing interactive here:

Later on, another article by the same Wired writer, Margaret Rhodes, shows us how Google’s deep learning AI plays such a mean game of Pictionary. And again, notice the trend towards managing ambiguity that these new methods are so good at.

“But the game’s accuracy, while impressive, isn’t what makes it a powerful learning tool. It’s how, by observing the way Google responds to your doodling... The lesson: To understand the whole, neural networks need pieces of data that not only connect but build on one another, piece by piece.”


WIRED, Apr 2016
WIRED, Nov 2016

Play with Neural Networks

Wednesday, November 16, 2016

Nothing Rhymes with Orange

Eminem on Orange 

Excerpt from Hidden Scents, 1st 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.

Wednesday, November 9, 2016


People used to eat mummies, back in the 1800’s. Image source: wikimedia

The mysterious always has a way of wiggling past our common sense. When mummies were first discovered by the West, they were the height of public wonder. To preserve a body forever, and in such a way, was a shock to the imagination. The powerful aromatics used in mummification enticed curious people with lots of money to buy the craziest thing out there – mummy meat.

Eventually, with the initial mother lode of mummies exhausted, and the market still demanding more, opportunists arrived – entrepreneurs, perhaps. They impregnated recent cadavers with aromatic substances, wrapped them up, and aged them until the time was right, when they would be passed-off as authentic Egyptian mummy meat. People devoured its wonderment all the same. It was claimed to have special effects on those who ate it. But what was more intoxicating, the meat, or its mystery?

One thing is for sure – the smell of spice, incense, the eternal, and the foreign gave tangible credibility to such claims.

This story is taken from Annick Le Gu√©rer’s Scent, the Mysterious and Essential Powers of Smell, written in 1988, translated from French in 1994.

Excerpt from Hidden Scents:
Odors only stimulate memory; they do not cause any other reactions by themselves. When one feels sick in the presence of an odor, it is not because of the odor itself but because of its association with previous sickness. Automobile exhaust smells and is deadly, but it is not deadly because it smells. The odor sensorium has no capacity for discriminating toxic from nontoxic substances. Odors are epiphenomenal, without any direct biological effect other than that on the olfactory system. Still, the powerful illusion that they cause pleasure and pain persists. Even when one knows that it was drinking too much whiskey that made one sick, the smell of it remains aversive as though it were the cause.* Because smell-response is learned, it only makes sense that upon repeated exposure to a smell, noxious or not, its alarming effect would wear off over time. Why else would you still be in its presence – “it mustn’t be dangerous” – and is therefore turned off, like a smoke alarm, disabled upon accidentally burning breakfast. Cognition is practically defined by its ability to move beyond this reliance on false alarms – it generates methods of identification completely unattainable in the detail and at the distance (both spatial and temporal) than that which is offered by olfaction.

*This is not to be confused with a “smell” that is trigeminally noxious. Mustard gas stimulates trigeminal nerves, not olfactory nerves. In fact, a good way to disambiguate smell from trigeminality is to determine whether it physically hurts. Smells do not hurt, they remind us of pain, but they do not physically cause pain.

Wednesday, November 2, 2016

Smell is a Sense More Suited to a Fluid Medium

Image source: The Human Brain, Rita Carter, 2009

Smelling started in fish. But that’s not exactly true, because responding to chemical signals is something that has been happening since life’s very beginning. Smelling with a brain...that starts with fish.

Neil Shubin, and ichtyopaleontologist (fish fossil finder), believes that the best roadmaps to our own bodies can be found in other creatures, as they carry the story of our development in their bones as well as their DNA. According to Subin's 2008 book Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body, there are two kinds of smelling genes in animals. One is for chemo-signaling in the air and one is for water. But certain surf and turf animals, the jawless fish (lampreys and hagfish), have both types, suggesting they arose before smelling genes split in two.

These jawless fish also have fewer odor genes. Over evolutionary time they increase – humans have hundreds. Many of our genes are non-functioning (and many are still in the process of evolving even today). Nonetheless, these junk genes remain in our DNA as a silent record of our evolution.

Geneticist Yoav Gilad found that primates who develop color vision tend to have more junk odor genes. Vision as an information tool de-emphasizes smell, thus turning more and more odor genes into junk. The (simple) advent of bipedalism takes us further from the data-rich olfactory carpet, while at the same time reinforcing the benefits of being so high up – we can see so much more this way!

It is no coincidence also, that the higher processing areas of our brain developed in tandem with the visual areas. Vision lends itself to cognition, whereas smell is limited to our emotions.

In the silent record of our evolution, manifest in our neuro-anatomy, is this separation between thoughtful human and primitive animal, the reflective and the automatic. To see is to understand. But to smell is to remember what it was like for the first organism to brainitself out of timespace, to be a jawless fish, a nematode worm, a plant whose roots wiggle through the earth, or the eukaryote "mindlessly" following the chemical gradient. There is no soil, no air, only fluid chemical signatures to activate and inhibit, and to be stored in memory forever.

Then again, they say fish only remember 7 seconds.