Today’s post is an interview with scent scientist Dr. Avery Gilbert, whose new book What the Nose Knows: The Science of Scent in Everyday Life is now available at Amazon. I haven’t received my copy yet, but in the meantime I read some of his research papers and found them very interesting. He has researched various aspects of odor perception at academic labs, he has worked for perfume companies such as Givaudan-Roure, and he currently has his own consulting firm called Synesthetics Inc.
Laurie: Dr. Gilbert, I’m wondering how you became interested in the science of scent? I read on one of your websites that it began with animal behavior studies?
AG: My first research project — as an undergraduate — looked at whether kangaroo rats could detect the odor of the Western rattlesnake which preys on them. They clearly could. After my brief snake-handling period I went on to graduate school to study sex behavior in rats and then mice. My first “human” experiment asked whether people can detect the odor differences that mice use to choose mates. (We can!) I became more involved in the human sense of smell and was eventually recruited to join the French-based perfume house Roure to set up a research program in odor perception.
Laurie: That sounds fascinating! Though the rattlesnake part sounds a bit scary… One of the teasers for your book says that you discuss the differences between how an amateur and a professional smell a scent strip. Can you tell us how that information might suggest better ways for people to test new perfumes for the first time? What could people do differently when they go to the perfume counter or get some new samples in the mail (besides not try them all at once!)?
AG: Part of the sniffing difference between pros and amateurs has to do with familiarity. Perfumers know the basic fragrance types and benchmark brands; they have a reference system in their heads. So when they sniff they quickly recognize the general type and then look for unique notes and key differences. They don’t spend a long time on a single blotter. Novice sniffers, in contrast, try to capture every nuance in an unfamiliar scent. They inhale so much the nose begins to tune it out. My advice is to sniff briefly and savor. Pause, then go back again to confirm your impression or to look for another element in the scent. It’s much like wine tasting.
Laurie: That’s really good advice. Treating it like wine tasting is something that people can relate to and would be a smart approach at the perfume counter to narrow down which scents to sample in more detail later at home.
On a different topic, some of your research has focused on the auditory and visual associations people make with scent. One of your research papers discusses how you found odor quality to correlate with auditory pitch. For example, birch tar, civet, galbanum, and caramel lactone were associated with lower-pitched tones while jasmine, olibanum, cinnamic aldehyde, neroli, and bergamot were associated with higher pitched tones. These associations are not true synesthetic perceptions in that people are not “hearing scent,” but they are consistently assigning relative pitches to a line-up of test odors. I find this really interesting because when I’m composing a fragrance I often think to myself that I need a “low note” or a “high note” and I’m unconsciously thinking in terms of auditory pitch. I’m not thinking about base notes or top notes in terms of longevity or fixation, but notes that sink low to the bottom of the composition to support it or that sing out high on top to add interest. Have you found that perfumers often think this way? Have you done more research in this area since the 1997 paper?
AG: One reason I explored the multisensory association between scent and auditory pitch was that perfumers have always used musical metaphors: notes, accords (chords), register, and so on. I know perfumers who routinely use their synaesthesia-like color impressions when composing (!) a perfume. It wouldn’t surprise me if others, like you, “listen” to the notes as they work. I’ve always wanted to explore the possible links between scent and other musical parameters like rhythm, timbre and key.
Laurie: That would be interesting! I’m not a musician so my musical metaphors are probably rudimentary compared to someone with more music background. I guess musical metaphors help because it’s hard to describe scent in words; musical metaphors seem to be a natural way to try to put words to the experience of scent.
On the color/scent association topic, your research found that people seem to associate specific colors with odors and that the color intensity increases as the odor intensity increases. You also refer to studies by others that show people judge food to taste and smell better if the food color is appealing (unless they are blindfolded). These types of findings, taken together, suggest that the color of perfume could affect its perceived value and quality; it’d be smart to make the color of the juice and packaging be a good fit for the scent. Does Synesthetics help companies with decisions like these? I use some natural ingredients that have a lot of color (such as labdanum absolute, oakmoss, lavender absolute, and myrrh); will the browns, greens and oranges of these naturals change the perceived value of the perfume? I don’t use artificial colors and wonder how much to worry about the color of my perfumes given their often richly colored natural ingredients; many other perfumers who also use high amounts of naturals must wonder about this too.
AG: In many of my client projects I use consumer testing to identify the color impression of the scent so that the packaging and advertising can be coordinated with it in a multisensory way. I’m a big believer in coherent sensory marketing — what good is it to take a juice that people perceive as bright and pastel and package it in dark, deeply saturated colors? When natural ingredients impart a color to the juice, my advice is to use the psychological scent-impression palette for the bottle, box and label colors.
Laurie: That really makes sense, and the idea of a psychological scent-impression palette is something for me to think about. Sounds wise to consider people’s reactions to fragrances when assessing suitable colors and packaging. Independent lines often pick one box and label style for all their scents, so your points make that choice even tougher and more important!
In another paper you mention the common problem people encounter when they sniff an odor “blind” and know they’ve smelled it but can’t put a label on it. You refer to this as the “tip of the nose phenomenon.” Do you know what causes this? Perfumers train themselves to recognize odors and put names to them, but without training and practice it is hard for most people to do. In contrast, if you play recordings of various sounds without showing images of the sound source, I bet people would be able to name basic sounds very easily. Yet sometimes people will sniff a bottle that smells like vanilla or cinnamon and say “sweet” but can’t name it, or they sniff a fruit smell and say “fruity” but can’t say which fruit. Why is it so much harder to put names to smells?
AG: The reason people have a hard time naming blind smells is that it’s an unnatural task. It’s tough to identify a smell in the absence of context. Outside the realm of raw materials and finished fragrances even perfumers have a hard time naming smells. However, people are quite good at judging whether or not a smell is familiar, and very quick to say whether they like it or not. I think that’s because these judgments have survival value and have been important to us for eons.
Laurie: That makes sense too. Did you find any interesting differences between men and women when you investigated differences in odor perception related to age and sex? Are women better at identifying smells? (I’ve heard rumors to that effect but haven’t seen any research.) Have you done any research into anosmia to musk chemicals? Are men or women any more likely to have more anosmia?
AG: Under laboratory conditions one regularly sees small but consistent group differences between men and women — usually in favor of women. Studies show women have the advantage in naming odors, something that goes along with their generally better verbal skills. On the other hand, pregnancy and phase of the menstrual cycle complicate the picture. Anosmia is an equal opportunity condition and I’m not sure anyone has yet found reliable sex differences in specific anosmia to musks.
Laurie: In your research, you found that people associated specific colors consistently with many test odors you presented to them. For example, cinnamic aldehyde was associated with red, bergamot was associated with yellow, and caramel lactone was associated with brown. These associations make sense to me based on correlations with the colors of natural things (cinnamon, citrus fruit, and caramel/maple/brown sugary foods, respectively) that would match the smell. Since perfumes are complex blends of many notes, the color/scent association becomes more complex. People do seem to associate warm oriental scents with richer, warmer colors like reds and ambers, while lighter, refreshing scents are more often associated with cooler paler colors, and floral scents are often associated with the colors of the flower. Is there anything else besides life experience that would contribute to the color we associate with smells? I realize this question is too involved to give a complete answer here…
AG: The origin of scent-odor associations is a matter of debate. Many people assume they arise from personal experience. But this can’t account for the consistency in associations we see between people, even around the world. I think there’s bias in the brain to attach certain colors to a given smell. The fact that more intense versions of the same scent produce darker associations in the same hue makes me think the brain is built to perceive things this way.
Laurie: That’s intriguing! It’ll be interesting to see if any follow-up research is done in that area. Thank you Dr. Gilbert for generously sharing your time with us for this blog today! This just gives us a hint of some of the topics you’ve explored in your research. I’m really looking forward to reading your book!
Dr. Gilbert’s new book What The Nose Knows: The Science of Scent in Everyday Life can be purchased at this link on Amazon:
He’ll be in the SF Bay Area to visit with northern California folks at the SF Borders bookstore on July 23 at 7 p.m. A schedule for all his appearances can be found here:
A review of his book can be found here at basenotes:
Edited to add: I just realized I should post the references for the research papers I read for the interview, so I’ve listed them below.
Gilbert, A.N., Martin, R., & Kemp, S.E. 1996. Cross-modal correspondence between vision and olfaction: The color of smells. American Journal of Psychology 109:335-351.
Gilbert, A.N. 1997. The evolving links between scent and color. Perfumer & Flavorist 22:53-54.
Belkin, K., Martin, R., Kemp, S.E., & Gilbert, A.N. 1997. Auditory pitch as a perceptual analogue to odor quality. Psychological Science 8:340-342.
Kemp, S.E. & Gilbert, A.N. 1997. Odor intensity and color lightness are correlated sensory dimensions. American Journal of Psychology 110:35-46.
Gilbert, A.N., Crouch, M., and Kemp, S., 1998. Olfactory and Visual Mental Imagery. Journal of Mental Imagery 22:137-146.