In the realm of fragrance reviews, many enthusiasts transform into critics. Taking the example of the fragrance pyramid with its top, middle, and base notes, some criticize reviews that focus solely on a particular phase. Others, aware that the fragrance pyramid may not precisely correspond to the actual scent, critique reviews structured around these notes. Recognizing that fragrances don’t strictly progress in three stages, some criticize reviews that rigidly categorize scents into these phases.
Today, I personally step into the arena to demonstrate where these inclinations might lead us, starting from the principles of olfactory perception. Without elucidating these principles, some may harbor the illusion of being the lone sober individual amidst a crowd of inebriated critics. Disagreement might be misconstrued as a lack of expertise or understanding.
Fragrance Reviewer:
A myriad of noses, a cacophony of opinions When describing scents in fragrance reviews, endless debates arise. For instance, large-flowered jasmine and small-flowered jasmine are both categorized as jasmine, yet the scent can vary significantly depending on the environment in which it grows. How do we establish a scale for the scent of “jasmine”?
Even if we temporarily set aside this issue and attempt to define the scent of “jasmine” as the unique fragrance of a specific jasmine at a particular time and place, it becomes impractical. This is due to the “individual differences” in olfactory perception. The variations are so vast that for a specific scent molecule, one person may detect sandalwood, another may sense a floral note, and someone else may perceive no scent at all.
Even if we use the perception of a particular individual as the standard, that person’s perception can subconsciously change due to the context. For example, adding colorless red dye to white wine can confuse even seasoned wine tasters. Simply altering the fragrance of a shampoo can make users feel that it cleanses better and leaves their hair shinier.
From these observations, it becomes dishearteningly clear that in everyday language, everyone is talking past each other. The exchange and understanding of fragrances are illusory, truly reflecting the idea that fragrance appreciation is as diverse as the number of individuals engaging in it. It seems that resorting to academic language or even mathematical formulas might be the only way to achieve consensus. But does this truly solve the problem?
Analyzing Perfume Reviews from the Perspective of Psychophysicists: Unraveling the Complex Relationship Between Physical Stimuli and Sensory Perception”
In the realm of fragrance critique, many enthusiasts transform into critics. Taking the example of the three accords in perfumery, enthusiasts who have learned about these accords often criticize reviews that focus solely on one phase of a perfume. Understanding that the three accords don’t necessarily correspond to real-world experiences, they critique reviews that revolve around these accords. Recognizing that perfume doesn’t strictly progress in three stages, they criticize reviews that separate the evaluation into three distinct phases.
In this discourse, I step into the field to showcase how such tendencies can lead us astray from the psychological and physical principles of fragrance perception. Without explaining these principles thoroughly, some might fall into the illusion of being the lone enlightened individual, misunderstood by others.
Perfume Critic: Diverse Perspectives, Varied Opinions
Describing scents in perfume reviews brings forth endless debates. For instance, both large-flowered jasmine and small-flowered jasmine fall under the category of jasmine, yet their aromas can differ significantly based on the environment in which they grow. How should we establish a scale for the olfactory perception of “jasmine”?
Even if we set aside this issue, defining “jasmine” as the unique scent of a specific jasmine flower at a particular time and place is impractical. Olfactory perception has inherent “individual differences” – significant enough that, for a specific olfactory molecule, one person may perceive sandalwood, another may sense a floral scent, and someone else may detect no odor at all.
Even when using one person’s perception as a standard, their perception can subconsciously change due to circumstances. For example, adding colorless red dye to white wine can confuse wine experts. A shampoo changing only its fragrance can make users feel it cleanses more effectively and makes their hair shinier.
Given these facts, the conclusion is somewhat disheartening: using everyday language, everyone speaks in their terms, and communication and understanding of perfumes become illusory – a situation of a thousand people, a thousand noses. It seems that resorting to academic language or even mathematical formulas is required to achieve consensus. However, can this truly solve the problem?
From a Psychophysicist’s Perspective:
Psychophysicists, who study the relationship between physical stimuli and sensory perception, employ various techniques to define variables, control factors, eliminate interference, measure visual, auditory, tactile, olfactory, and gustatory senses, and statistically analyze experimental data. They have derived laws in the field of psychophysics.
The first law, applicable to all five senses, is Stevens’ Power Law. This law states that the magnitude of olfactory perception is positively correlated with the intensity of olfactory stimulation, following a power function with an exponent greater than zero and less than one. In simpler terms, it describes the diminishing marginal effect of olfactory perception – as the concentration of a perfume increases, the perceived intensity does not increase proportionally but becomes increasingly challenging.
It’s essential to note the distinction between Stevens’ Power Law and olfactory adaptation. Olfactory adaptation refers to the weakening of olfactory perception over time when a specific odor stimulus persists in the environment. Stevens’ Power Law describes changes in olfactory perception along the dimension of stimulus intensity, while olfactory adaptation describes changes over time. Different odor molecules have different power law exponents, showcasing the remarkable results of mathematical modeling.
However, another crucial law in psychophysics, the Law of Summation, faces an awkward situation when applied to olfaction. While hearing perfectly conforms to the Law of Summation – for sounds of equal intensity, the total loudness perceived by both ears is twice that perceived by a single ear; for sounds of equal loudness and different frequencies, the total loudness is twice that of any single sound – combining two different odor molecules produces diverse olfactory perception relationships.
Even the combination of formaldehyde and ammonia, a seemingly straightforward pair, exhibits the following variations in pungency:
- At low concentrations: sub-additivity (the perceived intensity of the mixture is less than the sum of the individual intensities).
- At high concentrations: super-additivity or synergy (the perceived intensity of the mixture is greater than the sum of the individual intensities).
- At medium concentrations: standard additivity (the perceived intensity of the mixture equals the sum of the individual intensities).
Sub-additivity predominantly prevails in olfaction:
- Partial additivity (the perceived intensity of the mixture is greater than the maximum individual intensity).
- Intermediary (the perceived intensity of the mixture falls between the individual intensities).
- Suppression or compensation (the perceived intensity of the mixture is less than the minimum individual intensity).
- Symmetric suppression (odor molecules with equal individual intensities in a mixture decrease in perceived intensity equally).
- Asymmetric suppression (odor molecules with equal individual intensities in a mixture decrease in perceived intensity unequally).
- Masking (an increase in the concentration of masking components in a mixture causes a decrease in the olfactory perception of other odor molecules, such as the cork smell in wine).
- Covering (strong odor molecules completely mask the perception of weaker odor molecules).
Making things more complex, different facets of the same combination can exhibit different summation scenarios. The formaldehyde and ammonia combination mentioned at the beginning, considering only the pungent aspect, has three stages. However, when considering other facets, it consistently shows sub-additivity.
Even with the attempt to reshape perfume reviews using academic standards, relying solely on psychophysicists proves challenging. The complexity of the real world leads them to be confounded by exceptions, turning their diligent work into clumsy philately. Incorporating the biological aspects by introducing the physiological mechanisms of human olfaction might offer a solution, right?
Analyzing Fragrance Reviews from a Biologist’s Perspective
Richard Axel was awarded the Nobel Prize in Physiology or Medicine in 2004 for his groundbreaking contributions to olfactory research. His discoveries encompassed over a thousand olfactory receptors, unraveling astonishing similarities in the anatomical structures of olfactory organs and the functional logic of olfactory circuits between mammals and fruit flies. Yes, fruit flies. To cut to the chase, let’s delve into the confirmed olfactory physiological mechanisms so far, exploring both anatomical structures and odor molecule recognition.
Anatomical Structures:
At the top of each of the two nasal cavities, there is an olfactory epithelium with an area of 3.7 square centimeters. The olfactory epithelium consists of mucus, olfactory glands, and 12 million olfactory neurons. Each olfactory neuron extends 20-30 cilia toward the nasal cavity and expresses only one type of odorant receptor. On the other side, similar olfactory neurons bundle together to form olfactory glomeruli with secondary neurons called mitral cells, creating olfactory bulbs. Over 5,000 olfactory bulbs assemble into olfactory tracts, processing olfactory signals transmitted to the cerebral cortex, hippocampus, and hypothalamus. Molecules in the nasal mucus bind to odorant-binding proteins and other enzymes, transporting odor molecules from the nasal cavity’s air to the cilia’s surface. The cilia’s surface contains transmembrane G protein-coupled receptors that, through unknown interactions with odorant molecules or odorant-binding proteins, undergo biochemical cascades, altering the ion channel states of olfactory neurons’ membranes to generate electrical signals, conveying olfactory perception to the brain.
Odor Molecule Recognition:
Due to unknown interactions between odor molecules and odorant-binding proteins in the olfactory mucus, as well as interactions with other enzymes, and the unknown direct interaction between transmembrane G protein-coupled receptors on cilia surfaces and odor molecules, various theories, approximately 30, have emerged over the course of history to explain olfactory mechanisms. Considering that humans express only 396 odorant receptors but can identify 400,000-1 million odor molecules, the combination theory is currently the most accepted. Unlike the classical lock-and-key theory, the combination theory suggests that the relationship between receptors and ligands is not highly specific, and one odorant molecule may bind to many different odorant receptors with varying affinities. Conversely, one odorant receptor may bind to many different odorant molecules with different affinities. The stimulation by odor molecules no longer produces a single electrical signal but rather a pattern composed of multiple signals.
This is the most reasonable hypothesis for the human olfactory mechanism to date. It attempts to explain most phenomena at the receptor level. The significant differences in sensitivity to specific molecular odors among individuals can be attributed to genetic polymorphisms, expression differences, and distribution ratio differences in these 396 odorant receptors. For odor molecules, an average of three descriptive terms is needed to fully express their olfactory characteristics, which can be explained by the pattern of electrical signals in the combination theory. The different characteristics of the same odor molecule at different concentrations can be explained by the fact that higher concentrations can activate a greater number of odorant receptors. The harmony between fragrance notes is achieved because different combinations of signal patterns generate entirely new patterns.
However, the physiological factors determining human olfactory perception go far beyond the receptor level. This hypothesis does not explain the interactions between olfactory neurons, interactions between olfactory bulbs, the signal processing mechanisms of olfactory bulbs, the details of olfactory signal transmission to the brain, and the brain’s processing of olfactory signals, all of which could be reasons for the phenomenon of a thousand people, a thousand perceptions. To prove this hypothesis, there is a long way to go, and to date, humanity has not elucidated the crystal structure of even one olfactory receptor, let alone hundreds, and the neuroscience mechanisms at higher levels.
Alas, such is the plight of scientists. Faced with complex and challenging tasks, people often place their hopes in scientists, believing they always have a solution. However, rationality has limits, and science has boundaries. Even scientists themselves find their hair graying. I hope that in my lifetime, humanity can unravel the mysteries of the human olfactory mechanism.
Is Perfume Review Meaningful?
Upon reaching this point, readers may wonder, with the increasing understanding of the scientific principles behind a thousand people, a thousand smells, is academic exploration becoming an ever-expanding pit, seemingly insurmountable in the short term? Does this mean that communication about perfumes between individuals is impossible, rendering perfume reviews pointless? Here lies the crux of this article: perfume reviews are undoubtedly meaningful, and their significance is profound.
Even if we delve into the physiological mechanisms of human olfaction at various levels, armed with robust psychophysical models, an obsession with factual descriptions appears futile. Firstly, requiring everyone to possess a corresponding academic level to discuss perfumes is neither fair nor realistic for the general public. Secondly, even if everyone can understand chromatographic analysis results and interpret electroencephalograms, the distance between this knowledge and perfume appreciation is as vast as knowing the chemical formula of water to understanding fluid dynamics.
In all psychophysical studies on olfaction, measurements are achieved through the subject’s language expression, tapping into the higher functions of the cerebral cortex. However, as described earlier in the anatomical structure of the human olfactory system, olfactory signals from the olfactory bulb not only reach the cerebral cortex but also extend to the hippocampus and hypothalamus. Throughout evolution, while the human brain underwent profound changes, the olfactory circuit remains ancient (recall the similarities between human olfaction and that of fruit flies), directly connecting to the hippocampus and hypothalamus.
In perfume appreciation, when olfactory signals reach the hippocampus, they trigger memories, and reaching the hypothalamus triggers emotions, bypassing conscious pathways and operating in the realm of the subconscious. Within the subconscious lie a myriad of elements shared by all but spoken by none. What perfume reviews aim to achieve is to, in advance, bring forth what is stimulated in the subconscious into consciousness, responding to the collective unconscious’s desires. This does not imply advocating for carefree and arbitrary writing; rather, writing a perfume review requires exceptionally skilled language abilities to express truths beyond technical details, reflecting an essence of human life embedded in the perfume. This is why perfume is considered an art.
Conclusion:
In conclusion, let us draw upon the closing words of Chapter 3 in the first volume of “The Feynman Lectures on Physics”: “A poet once said, ‘The whole universe is in a glass of wine.’… If we were to look closely at a glass of wine, we could see the entire universe… If we, for convenience, divide this glass of wine, this universe, into parts – physics, biology, geology, astronomy, psychology, etc. – remember, nature does not know it. So, let us put it all back together and not forget that the final goal is for this wine to give us joy once again!”
Now you understand why everyone’s sense of smell is unique, right? Our perfumes should not only please ourselves but also not disturb others, all while showcasing our taste. This is a process that requires training and exploration. Therefore, before purchasing a full-sized perfume, buying a sample is the best trial-and-error method. Find your signature scent, and begin your journey with Branddecant.