Tuesday, September 28, 2010

The Vintage Nose: Scent and How We Smell It.

Sometimes it's necessary to step back and think about how we smell as much as it is about what we smell. Many have attempted to devise a comprehensive theory of scent without resounding success; the most popular current theory is built around the so-called" lock and key" model. In this scenario, the shape of a molecule determines the characteristic of its scent. According to this system, there are seven primary smells: camphor, musk, floral, peppermint, ether, pungent and putrid.

Of course, other theories have been championed over the years. Being a vintage spirit and feeling closer to the perfume creations of the past than any of the current parade, I chose to look backwards for inspiration and to understand how it is that we know what we smell, to the time when the beautiful archetypes of modern perfumery were emerging from the ether of their creator's minds...

It's been nearly one hundred years since L'Origan /L'Heure Bleue , Chypre/Mitsouko, Tabac Blond / No. 5 were called forth from the foundations of modern perfumery. Is it any mistake that Hans Henning's great work titled Der Geruch (The Odor)- was published at this same intellectually inventive and revolutionary time?
Coty Emeraude released in 1921
Henning's system for classifying scent is as intriguing today as it was then and quite possibly, as advanced.

Henning was among the first generation of German experimental psychologists to follow Wilhelm Wundt (1830-1920, widely regarded as the father of experimental psychology). Henning brought a scientist's training and background in chemistry to bear on his work in the area of human perception and olfactory experience. At the time his work was regarded as daring and very critical of the then-current-and- accepted theory of smell, essentially derived from the work of Linnaeus-Zwaardemaker.

For your clarification: The Linnaeus-Zwaardemaker system divided scents into the following nine categories: ethereal (beeswax), fragrant ( flowers), aromatic (camphor spice), ambrosiac (amber/musk), alliaceous (onion/garlic), empyreumatic (coffee/smoke), hiccine (sour milk or spoiled food), foul (decomposing), nauseous (rotten eggs, feces). Aside from a preponderance of unpleasant categories (almost half), and some notable contradictory examples, the Linnaeus-Zwaardemaker harkens to the currently favored classification of seven primary smells- so it seems little has changed.
Of extreme interest here, especially pertaining to those of us who enjoy reading and writing reviews of various perfumes based on our smelling of them is Henning's finding that....reliable judgments... can be obtained only from observers who do not know the nature of scents with which they are dealing.... This requirement on anonymity in judging smells lies in the difference between the object's true odor and it's "object smell". The "object smell" refers to what happens when the true odor of a scent is influenced by what we see and know (and think!) about the supposed source of the odor. Our perception of scent is richly informed, to say the very least, and completely over-ridden to say the most, by our cognitive processes, through the device of associative supplementing.

                                                Ian Cooper's Dream Journey
Not to fret, we do the same thing with most other sensory processes - fill in the missing bits with internal ones largely manufactured based on our past experiences, memories, and expectations. Turns out, it's easier for us than constantly processing all the incoming information that is really coming in. In the case of vision, we modify colors, lines and shapes , even invert the whole thing once the picture is formed- to form a unified visual experience of our world. Even though our eyes dart back and forth and shift focus constantly, we perceive a continuous, uninterrupted field of vision.

But it is to say that there is real value to reviewing scents "blind" and to descriptions given in the absence of a list of notes or a bit of press copy.

According to our reviewer, Henning's work makes four important points about scent and smell.

Firstly he presented a new shape or schema to represent the interrelatedness of smells- in his vision, the arrangement forms.... a tridimensional manifold, with groupings of odors represented along a prism with equilateral triangular faces and the rectangular faces squared. It might be hard to imagine so here is a picture:

Anyone else thinking: Dark Side of the Moon?

Anyway, at each of the six angles stand his six (not nine or seven) characteristic smells. Along the triangle faces, floral mirrors spicy, fruity with resinous and putrid with burning/smoky smells. Violet is considered the most typical floral scent, lemon the most typical of the fruity group, sulphuretted hydrogen of the putrid, nutmeg of the spicy, frankincense of the resinous and tar of the burning groups of scents.

There are transitional smells as well, leading from each class to another. The classes which stand opposite each other on the square faces of the prism are regarded as connected to each other through transitional scent characteristics.

Examples of these transitions: between flowery and fruity is geranium and sandalwood; between flowery and putrid is decaying flowers; between fruity and putrid, various stages of decaying fruit; between flowery and spicy, thyme and vanilla; between fruity and resinous (includes woods) various piney odors... Between putrid and burning / smoky, come the ammoniacal/animal odors; between flowery and resinous are fragrant gums (labdanum); between fruity and spicy, the mints (and anise), between putrid and spicy is garlic; between putrid and resinous comes fish scales (and I imagine, leather would fit here too), and between burning and all other classes, the odors obtained by burning or smoking items of those classes.

BTW: I find this system much more evocative of my experiences with scents and smells but what about you?

According again to our reviewer, the smells at the angles of the prism are related in a like way as colors are but the smells occurring along any edge or diagonal are more like tonal variations. There is also some description given in Hennings work to the dispersal of scent groups along the plane faces and the existance of scents within interior of the shape- and discussion about where mixtures exist, that really complicates the discussion and goes well beyond my aim to be somewhat relevant and entertaining.

I do admire very much that all of this classification was experimentally derived by Henning in his lab. He asked scores of subjects to categorize scents under a variety of conditions and built his system from his impressions of their responses. I also admire that he resisted or rejected the use of frank statistical analysis, knowing as most clinical scientists (and artists) do, that his trained impressions of the raw data were of primary import.

Secondly Henning's work strongly refutes the widely accepted notion of a compensation or cancellation effect in scent. Rather he found waxing and waning in the ability to perceive scent to be due more to physical effects of successive smelling of individual components in complex mixtures. The primary elements emerge in the recipient's awareness as they coalesce and separate, due to localized shortages and abundances of molecules and admixtures produced as the scent volitalizes. Or at the other end of the casual spectrum, he speculates it is due to one's shifting attentions. Our book reviewer has an even more plausible suggestion. See below...

Thirdly, Henning refutes scent exhaustion. It is noted to be more likely a simple case of sensory adaptation due to diminishing attention to persistent stimuli. One of the more convincing cited evidences against scent exhaustion is the fact that strong noxious smells cannot be exhausted, as much as might be wished. Further we now know that nasal mucosa and epithelium are renewed and repaired in an ongoing process and unlikely to be damaged or rended exhausted. Scent molecules are broken down almost as soon as they have been absorbed and assimilated. Non-poisonous scents alone do not appear to damage or impact the functioning of the sensory organ anymore than viewing colors, movement etc does not damage or exhaust the eyes (strong sunlight is damaging via another mechanism). Sensory adaptation is well documented with other senses and may have both peripherally and centrally mediated mechanisms in regards to scent perception.

Lastly Henning's work draws parallels between scent and perception of color and taste - all can be organized according to his basic prismatic structure. For example, besides the traditional sweet - salty - bitter - sour categories of taste, he identifies the following transitional tastes: between sweet and sour, bicarbonate of soda; between salt and sweet, alkaline; between salt and bitter, potassium bromide; between sour and sweet, acetate of lead, between sour and bitter, potassium sulphate and between sweet and bitter, acetone. The phenomena of taste mixture is said by Henning to be very similar to the concept of smell mixtures.

Of all of this, the thing that really sticks with me is the equilateral triangular prism and the categorization of Henning's scents, which strikes me as elevated. And if I was a perfumer, I would think it should be quite inspirational. And so I dream of a lemon-violet, nutmeg frankincense haze embellished with just a touch of smoke and the merest hint of decay... Perhaps a new Shalimar waiting to be born?

The Vintage Perfume Vault, where the scent of yesterday's vogue lives.
Note: this article is based on my reading of a book review of Der Geruch by Hanz Henning, Leipzig Barth, 1916. The book was reviewed by E. A. McC. Gambel of Wellesley College for volume 32 of the American Journal of Psychology. I have only read her review and excerpts of the original.

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