Tuesday, September 25, 2018

When It Rains It Smells


In English, the smell of rain didn’t have a name until 1964. Some mineralogists from Australia really wanted to figure out where the smell came from, so they did some experiments. In order for them to describe their results, they took the liberty of changing the pretty useless term for the smell of rain, “Argillaceous odor,” to “Petrichor.”

Argillaceous refers to things made of clay, and petrichor in Latin means rock blood. “Argillaceous” is not exactly the smell of rain, but the smell of wet clay (an odor I know very well as a potter). The word refers to the clay (argilla, Latin) and is used in the absence of the other smells that come from soil, like that which comes from grass and other plant matter as well as the microorganisms and fungi that live in fertile soil.

The main organic ingredient we aren’t mentioning here is “Geosmin.” This doesn’t come from rocks, but from a certain bacteria that lives in the soil, and we all know it as the smell of freshly disturbed earth (geosmin: earth+smell, Greek). Coincidentally, geosmin was named at almost the exact same time as petrichor, in 1965.

With Petrichor, the study authors wanted the semantic identity of the smell to be no longer limited to soil, but all the things that make it what it is. (They also used the phrase “osmic latitude” to refer the general smell-space of a smell, which is another valuable term for the olfactosphere.)

Their main purpose was to pinpoint the source of this ephemeral entity, detailing the variables that make it so – porosity of the clay/soil medium, makeup of the minerals, dryness of the medium prior to wetting, and the presence of both living and dead biological components, like geosmin.

In their pursuit they concocted all combinations of minerals, torched them to eradicate any organic matter contamination, and then literally sniffed the results (using only wetware, i.e., their human noses). Ultimately, the only thing I can tell you from their work is that soil with the most silica produced the sought-after results prodigiously.

An Ancient Recipe for the Smell of Silica
Then there’s that little village in India that’s centuries ahead of our Australian scientists – they bottle Petrichor and sell it as perfume. Four months of the hot, dust-blown summer in northern India does a good job of preparing a fragrant medium for extraction.

In the case of Petrichor, the drier the medium the stronger the scent released upon being wetted. This is because the dirt is absorbing the essential oils of the biosphere (terpenes floating in the air) as well as harboring micro-organisms, fungal colonies, and other plant matter in general. The longer it has to absorb, the more it accumulates – a ticking scent-bomb in a place like India where it doesn’t rain for quite a long portion of the year.

And then come the monsoons, releasing a warm, mineral-rich, and momentary fragrance. It’s a scent that has so possessed a population that they go to great lengths to capture it. Before the monsoons arrive in July, they remove a bunch of this sun-baked earth and fire in a kiln to get it super-dry. Then they distill the essence out of it.

The most interesting part is that this is the only attar they brew that does not come from a plant. And it’s true – what the Australian scientists proved was that it’s mostly silica dust.


Osmic Vernacular
The smell of rain speaks in many different tongues. Because the smell of rain depends so much upon what it wets, it’s different everywhere you go. Surely, one archetype of this scent comes from the parts of India where it’s very dry for a very long time, and then all of the sudden the monsoons come. Personally, I’ve never been to India, so if I smelled a bottle of “rain attar” it wouldn’t exactly send me into a nostalgic reverie. City rain, my kind of rain, smells like steaming asphalt. In lush and verdant West Africa, it smells different again.

This has a lot to do with the dynamics of aerosolization, which isn’t too hard to understand – millions and millions of raindrops smash into the earth, the impact sending tiny particles of whatever it hits shooting into the air. If you can picture it, this isn’t much different than an asteroid impact, only smaller. Argillaceous silica dust, bacterial metabolites, and all the other organic matter that covers the ground (including microscopic pulverized asphalt and other building materials) is sent flying so high into the air, that plumes of it can travel miles away, stirring thirsty cattle that can’t wait for the rains to come.

And let’s not forget ozone. Right before that rain falls, if there is an electrical charge in the air disturbing oxygen molecules, we get the smell of ozone (sharp, chlorine, burnt wires?). Oxygen molecules are usually paired together, but when the electrical activity in the air splits them apart, they can reform as three-molecule-oxygens, which are the only ‘version of oxygen’ that we can smell. (In fact I’m not certain that ozone-smell is oxygen; I’ll bet it’s more complicated than that, like how “chlorine” is not chlorine but the things it binds with, so that the more “chlorine” you smell in a pool, the dirtier it actually is).  

A concluding thought – the smell of rain has a lot to do with the smell of dirt and rocks and bacteria, and even with the smell of the air, and yet nothing to do with the smell of water.

Bear, I.J.; Thomas, R.G. Nature of argillaceous odour. Nature. 1964; 201(4923):993-995.

Geosmin, an Earthy-Smelling Substance Isolated from Actinomycetes. NN Gerber, HA Lechevalieh, Institute of Microbiology, Rutgers University, New Brunswick, New Jersey. Applied Microbiology, Vol 13, No 6, Nov 1965.

Making Perfume From the Rain, The Atlantic, 2015

Lexical Smell Network

New Jersey Turnpike during a rainstorm

Buy Geosmin on Sigma Aldrich!

This is the chemical name for geosmin:

Odor Descriptions of Geosmin from The Good Scents Co.
Fresh, humus, earthy, musty, freshly ploughed soil, the first rain after a dry period, dirty, weedy, wet, turnip, beet, the muddy smell in freshwater fish, the smell of the countryside

Some important bacterial players in this osmic drama:
Streptomyces coelicolor and Streptomyces griseus, of the Actinomycetes type mold

Post Script
Agrillaceous reminds me of Alliacious, another smell-word for things resembling or consisting of onions or garlic. It’s the first word in my lexical smell network, and I had certainly never heard of it until I began the project.

Geosmin can be made into argosmin, which is the same thing but doesn’t smell at all (Greek – argos =inactive…sound a little like argillaceous?)

And finally, because this is just a cool bit of trivia, geosmin has a hardline to the limbic system of the fruit fly – just the smell of it will activate an escape response, making sure they don’t lay their eggs in food spoiled by this potentially bad-news bacteria that creates geosmin.

Ovipositing btw, is the name for laying your eggs (de-positing , that is).

Friday, September 14, 2018

Limbic Resonance

Humans are the biological boot system for AI, and other prescient statements from Elon Musk. (Illustrated by Joe Scordo)

Above we see illustrated the Tripartite Brain, a rudimentary understanding of different modules of brain activity, as told through an evolutionary development paradigm. Our brains evolve first to do movement and navigation – this is the limbic system. Note the word “limb” in there. It controls the limbs but it also contains the senses, which then control the limbs. (Illustrated by Joe Scordo)

On top of that, we have the animal brain, the monkey brain, or the social brain. This is the one that makes us drink alcohol and paint ourselves in the colors of our favorite football team, sort of. And then there’s the cortex. This is the one that lets us talk to each other, make art, and do things that calculators do. What you don’t see here is the exocortex. I will credit Jason Silva with that, but surely someone else was saying it before him.

In a recent interview between futurist-entrepreneur Elon Musk and entertainment personality Joe Rogan, Musk talks crazy talk about brains and computers and most importantly computer-brain interfaces.

I’m writing about it here because he spends a few minutes in this exchange talking about the Limbic System, and that doesn’t happen much in popular news.

The topic comes up as Musk is shedding a bit of light on another venture of his – a system that can connect a computer directly to your brain. Crazy as it may sound, there has already been such sorcery for a while now, from the straight-up plug-in-the-head to the more recent eyeborg who hears his colors instead of seeing them, to the pretty ubiquitous EPOC headset. These are called neural interface systems (NIS) and you’ll surely be hearing more about them in the coming decade.

This image is courtesy of WIRED magazine, circa 2005

The EPOC headset has gone through a few iterations so far. A point I must make here, I bought this circa 2011 with the intent to use in the classroom, so my students could play silly video games with their thoughts, and be inspired by a future of wonder, and I was hit with the reality of racial bias even in the future, because students with afro-curl hair, even close to their heads, could not get a good connection from the electrodes, and so it wouldn’t work for them. Racial bias can show up anywhere and we need to be vigilant against it, just saying.

Musk describes his reasons for wanting a high bandwidth, direct link from computer to brain. As humans, we have the cortex, this highest form of a biological computer that we know of. Sure, we can instead call a computer the highest form of a cortex that we know of; in fact, this is where the term exocortex comes in. Currently, we do not have direct access to this exocortex the same way we do the regular cortex.* And that sounds like a job for Mr. Musk. All we have are fingers, and nowadays our voices, and for some people eye movements or other gestures. These ways are too slow, not enough bandwidth.

Musk, in a roundabout way, blames this on the limbic system. Because we have to use our bodies to interact with computers, we have to go through this ‘archaic’ neural network first. Why can’t we just connect the cortex directly to the exocortex?

In the midst of this, he mentions how the internet today exhibits “limbic resonance,” meaning it has been essentially programmed by our collective limbic system. For example, social media is run partially by algorithms, but partially by us and our reptile brains. And according to Musk, as long as we still have these meatbodies in between us and the computers (read cortex and exocortex), then the internet will be an outward reflection of our inner reptile.

And so there you have it, the limbic system in the news. Appreciate it now because it doesn’t happen often.

*”Regular cortex” is called a retronym, or it will be when we come up with the name for it. There was no such thing as an “acoustic guitar” until the electric guitar came out. Might as well start thinking about it now – what will we call the ‘regular cortex’ once the exocortex becomes ubiquitous?

Thursday, September 13, 2018

Are Terpenes the New Antioxidants

Limbic Signal's Terpene Lexical Network. 

Just kidding about the antioxidants thing. I’m really into the words we use for smells, and words in general. So I’ve definitely noticed the word Terpene come on the scene. It’s the magic word in the cannabis industry right now. Terpenes are ultimately the plant-secreted oils that give the flower its aroma. In other words, they are the smell of pot, both the good and the bad smells.

Terpenes are already an important part of the olfactory world, as they are the primary means of communication among plants, bacteria, and insects. And you can probably call the essential oils of plants something else, but terpenes sounds pretty cool, so that’s it.

For all its popularity, there have been few attempts to quantify directly the olfactory profiles of the cannabis industry. I’m talking about using legit hi-tech smell-sniffing machines; nobody had done this yet. We hear about ‘skunk’ and ‘citrus,’ but we haven’t tested a group of words for its usefulness in describing cannabis in all its olfactory instantiations. (There’s a pretty good reason for this, i.e., Federal law; see below.)*

He Smells an Opportunity
Sensory scientist Avery Gilbert was quick to notice this Lingua Vacuum, and quick to provide the solution. First he created a company that will now be known as the promulgator of the cannabis odor vocab – Headspace Sensory. He then wrote himself a study, got approval for testing, scored some product off the recreational market in Colorado, along with some equipment, a labspace and some volunteers, and here we are with a rigorously tested lexicon – 48 words that can satisfy most descriptions of most of the cannabis on the market today.

There were some great results from his work, especially regarding false associations between odor description and expected potency. I’ll go into that shortly, but first I should describe how he did all this. Because you know, details matter.

The cannabis product itself was chosen to represent a comprehensive sample of what’s out there (Lemon Diesel, OG Kush, Snoop OG, etc.). As for the words to use for describing the aromas of these different products, he did what any serious, academically-based person would do – he went to Leafly, and took a bunch of their olfactory-descriptors (earthy, musty, spicy, fruity, etc.). I also did this when I made my terpene chart, check it out here. The list he generates is deliberately over-inclusive, which means there may be redundancies as well as unlikely terms. This is a move I totally support, as olfactory identity has a lot to do with the margins and the seemingly extraneous.

The next step was to mechanically “sniff” the products, producing an analysis of the physical chemicals evaporating from them (Limonene, Myrcene, etc.). And finally, he asked real humans to sniff those same products, and choose from the list of potential descriptors enough words to satisfy a worthy olfactory articulation.

On To the Results
The overall purpose here was to survey the limits of an olfactory lexicon for cannabis. How many words do we really need to accurately describe all the cannabis that’s on the market? Avery concludes with 48 words, clustered into two major groups of 1) citrus, lemon, sweet, and pungent and 2) earthy, herbal, and woody in the other. For reference, similar lexicons for coffee and wine cover about 85 words.

Here’s the total list; I also typed it out below:
Headspace’s Terpene Lexicon

Time for the interesting part. Exactly as you would expect (had you read my book that is), smells have confused us. In Gilbert’s study, pot samples in the Citrus group (citrus, lemon, sweet, and pungent) were expected to be more potent than those in the Earthy group (earthy, herbal, and woody). Coincidentally, my terpene chart seen above does the same thing, clustering the same descriptors in the middle because they are the most common among all the terpenes. For whatever reason, people associate that citrusy-sweet-sour aroma with THC. For the record, THC does not smell. I am curious as to what others think about the reason for this, although I am sure it’s complicated (and has nothing to do with the fact that the citrusy-pungent profile made its appearance on the scene in tandem with higher potencies?). Anyone who’s been reading High Times since the early 90’s, feel free to weigh in!

Deeper into the olfactory funky skunk lexicon, Gilbert found that “bad” smells were associated with “good” stuff, and vice versa. In other words, the skunky, pungent, sour diesel, etc. flavors shouted DANK! while others whispered weakly, “you just got beat,” which also translates as “backyard boogie.”

This is great and I could talk about it forever, as it takes us to one of the most important things to know about our sense of smell – it is totally hedonically neutral, and totally malleable. Parmesan cheese is supposed to be gross to us, because it is rotting animal proteins. Kimchi is rotting cabbage. But some humans have been trained by their culture to like Parmesan cheese and kimchi AND the bad-smelling parts of the cannabis plant. That’s how smells work. There are no good or bad smells, only a code written by our culture over time.

Transgressing Cultural Limits
There’s something special about liking something you’re not supposed to. It becomes part of your identity. Most Americans like Parmesan cheese as a result of the Italian-American axis of culinary identity that is the pasta dinner, so it’s not the best example to use here. But kimchi has seen a sharp rise in popularity since it was “discovered” a handful of years ago on a taco truck somewhere on the West Coast of the United States. And now, people who like the smell of it have some kind of cultural advantage over others. Twenty years ago, it would have been a reason to spit ethnic vulgarities (and they smell so bad like rotten cabbage!), but today it does the same thing, only in the other direction (what a loser, I guess he can’t handle the smell of rotten cabbage in his tacos!).

If this is a topic you’re interested in, check out the essay “Quantum Hedonics” in my book which you can find on Google books for free.

If you recall, there was a time in your life that alcohol tasted like poison (alcohol is also fermented btw). Even sex has smells that at one time were pretty offensive to your younger self. But as we mature, the “acquired” taste for these things becomes a badge we wear as proof of our journey into adulthood and independence. The smell of cannabis is no different. To come to appreciate these “negative” properties of a thing is a cultural transgression that works in perfect concert with the illegal/taboo nature of consuming drugs, as well as the liberating effects of consciousness-expanding substances.

Perhaps it is the last two parts of the package that drive such a strong preference for the “bad” smells of pot products. Gilbert, in his report, makes it a point to mention that coffee and wine do not present skunky smells in a positive light – they are instead seen as a defect in these products. Beer however, which does not have its own aroma wheel like wine or coffee, suffers from being skunked just the same. And yet, as IPA’s have dominated the craft market, it should make you wonder whether the skunky-hops flavor of those beers are another example of consumer desires to transgress olfactive-cultural boundaries.

Concluding Thoughts
Thanks to Gilbert we now have a proper list of words to describe these products. It allows us all to be on the same page, and it furthers the growth in this budding industry by educating producers and consumers alike, and by providing a consistent basis for comparison among different products. More importantly, as far as I’m concerned, it gives us a baseline of data (a bunch of words) that we can use to make further discoveries about our own quirks, misunderstandings and cognitive-perceptual fallibilities.  

*The primary reason for this lack of research is that cannabis is still deemed illegal by the same entity that grants the right to conduct experiments on humans. In other words, in order to do any experiment that involves humans, one must secure approval, basically proving that their experiment won’t hurt the people involved. But that entity could never allow an experiment where illegal products are used. This is the state law/federal law puzzle that keeps things interesting here in the US.


Avery Gilbert’s Source Article:
Gilbert AN, DiVerdi JA (2018) Consumer perceptions of strain differences in Cannabis aroma. PLoS ONE 13(2): e0192247. https://doi.org/10.1371/journal.pone.0192247

Avery Gilbert ‘s Blog:

Terpene Network Graph:
I made this terpene graph where I took all the top terps from Leafly, and their corresponding descriptors from the Sigma Aldrich catalog, and made an interactive chart out of it (interestingly, my list has 49 words).

More Terpene Experts:
Oren Cohen is an olfaction artist and the founder and CEO of Terpene Experts. He is an olfaction artist and educator who specializes in terpene profile development, as well as providing professional flavor and fragrance creator for a decade, with deep experience in cannabis, e-liquid, and the restaurant industry.

Here’s What They Do:
We are terpene profile artists who can replicate the exact nuances of any strain in world. Our expert noses can smell a bud and detect the nuanced notes of its terpene profile with accuracy that comes from years of work as flavorists and fragrance creators. This is an art and skill that no lab report can replace. AND they create new terpene spectrumsss.

And Why They Do It:
“When people use cartridges or pens, the entire experience and expectation is different than that of flower. They want to enjoy the flavor. They want the key profiles of their favorite strains to present themselves in a layered and cohesive fashion. It’s our job as expert terpene flavorists to deliver an experience that’s both familiar and compellingly unique to the delivery system.”

Learn More About Terpenes:
An Introduction to Terpenes: A four-week course with Oren Cohen to explore the origins, profiles and uses of terpenes at the Institute for Art and Olfaction in Los Angeles.

Leafly terpene article:

From Avery Gilbert’s Study: The 48 odor descriptors used to characterize cannabis samples:
blue cheese
tree fruit
tropical fruit