Stop and Smell the Roses: Again....and Again!

While recounting an experience, we routinely resort to visual and listening devices to recreate the event. We employ our own voice, videos, photos, music and even hand gestures to communicate the message. Effective pedagogical methods, especially for younger students, invariably recommend audio-visual aids. Police investigation relies on witnesses' recall of sights and sounds at the scene of crime. But we are hardly ever called upon to recreate the memory of a smell. Nobody asks: "How did the ocean smell on your last visit to the beach?" or "What type of perfume was the bride wearing at the wedding?" The police does not ask the witness to describe the body odor of a suspect (although they employ dogs to sniff out the culprit). Yet, sight and sound do not comprise the totality of the information we gather from our environment. Our sense of smell is a powerful component of our physical experience and our memory.

For one thing, even if somebody did ask, we'd have a hard time describing a smell accurately. We don't have objective standards for measuring smell. Nothing like the color spectrum.  No scale, pitch or timbre that can be imitated to reproduce a sound. For smells we use adjectives like "overpowering," "fruity," "pungent", "appetizing," "stale" etc. We have formulaic words for smell such as "bouquet," "aroma," or "stench."  The best we can do is to compare a new smell to another familiar one. We resort to evocative similes such as "the restaurant stank like a musty cellar," "her hair smelt of green apples," "he reeked of alcohol and tobacco," or "the garbage smelt like rotten eggs."  We even use abstract concepts to denote smells: "a smell like death," "the smell of spring (or monsoon) in the air."   Most of the time we get the idea, provided we have ourselves experienced the smell of reference.

Impossible though it is to put in words, we are constantly reacting to our environment through our sense of smell. Our appetite, our feeling of cleanliness and well being, sexual arousal, are all affected or stimulated by smells. We even smell danger. Such as in the case of a fire, we frequently smell it burning before we see its light or feel its heat.

Smells are also powerful reminders of our past experiences. It has been established that the olfactory memory stays with us long after visual memory has faded. Vivid childhood memories are very often associated with smells. We clearly remember festive days, our mother's cooking (and her scent) and even mundane household routines from associated smells. Most of us who are parents, forever remember the happy smell of an amalgamation of baby oil, baby powder and milk which dominated our senses when our children were babies. A particular scent in one place reminds us of another one far away. I for one, associate a special smell with every house I have lived in and many cities I have visited. The smell of wet earth (rarely replicated anywhere outside India during monsoon) reminds me strongly of the first rainy days in Delhi after the scorching heat of summer. Particular brands of soap, perfume, spices, tobacco etc. remind me of different persons in my life. A pleasant smell does not necessarily evoke pleasant memories. A friend of mine could not stand the smell of sandalwood incense because it reminded her of the day her grandfather died and the house was redolent with the fragrance. And peculiarly enough in my case, the rather noxious stench produced by the intermingling vapors of benzene, acetone, ethyl alcohol and acetic acid, the stock odor of all chemistry labs, floods my mind with pleasant memories of many earnest hours spent as a student and teacher of chemistry. 

The reason our sense of smell is somewhat of an enigma and is often termed our "forgotten sense," is that unlike sight and sound which require physical stimulii, smell (as also taste) is a "chemical sense." Our olfactory system reacts to tiny smell bearing molecules in the environment which waft into our nostrils. The replication of a smell requires mixing natural or synthetic molecules in the exact right proportions. This takes time and a system of trial and errors. The billion dollar perfume and cosmetic industry devotes many painstaking hours to test, perfect and market their aromatic wares. Scientists in Japan are currently busy trying to develop a system of gadgets and sensors which will be capable of reproducing smells instantly after sniffing it -an olfactory equivalent of a tape recorder. If successful, the real life applications are countless.

"The first thing that hits you when you enter Professor Takamichi Nakamoto's laboratory is the smell.

Wafts of fried beef and onions, the rich smell of Japanese curry and even the obnoxious smell of rotten eggs all mingle together in the cramped room.

But the stench is not the product of an absent-minded professor surrounded by the detritus of late night snacks snatched during marathon experiments. Instead, the aromas are intimately tied to the Professor's work.

Based at the School of Engineering at the Tokyo Institute of Technology, Professor Nakamoto is building a range of gadgets and sensors which sniff, mix and pump out a range of hundreds of scents.

Fruity fragrance

One of the most ambitious devices his team has built is a sophisticated "odour recorder" which can sniff an object and then reproduce its smell using a host of chemicals.

If you present the recorder with a shiny red apple, the electronic nose will take a cursory sniff, analyse the odour and then draw up a recipe of chemicals needed to recreate it. When you want to replay the scent, the device mixes the ingredients and pumps the smell of apples back at you.

"Our intention is to make all smells reproducible," Professor Nakamoto said. "So, in this case we have combined two techniques: smell detection and smell generation."

At the moment, the prototype can only reproduce certain fragrances, including apples, bananas, oranges and lemons.

Read the whole article here.

Note: The article above was originally published here on October 17, 2006.  I am bringing it to the front page for two reasons. One, I can think of nothing substantive to write. Second, Razib at Gene Expression recently posted an article which ties up nicely with the post. It describes more precisely why our olfactory sense is a highly personalized attribute.

One more article on odor perception from the Scientific American.  

Comments

[John Emerson]

Anybody can produce the banana smell (amyl acetate).

[Sujatha]

Interestingly,over the years, I've developed a reduced tolerance to 'chemical' smelling perfumes of any type (some catalogs make me toss them in the dustbin, just to get rid of the sampler of 'Eau d'Issey', 'Pure White Linen' or whatever they are hawking.) I can deal with the acrid odor of sweat, even more than some of the wafts of perfume and deodorant. Ditto for the 'perfumed candle' aisles that are de rigueur at every self-respecting store, no matter what their mainstay is.
But one of the hardest to forget is the smell of burning flesh- a sickly sweet odor that we once had wafting for about a week over my neighborhood in India, because the local custom permitted the bereaved parents of a drowned teen to cremate his body in their backyard if 'nobody objected' (which everyone was reluctant to raise, since the family in question had once owned all the surrounding property before it got sold and subdivided into residential plots.). I can only imagine how inured crematorium workers would have to be to such odors.

As for 'recreating' odors by mixing and matching chemicals, I'm sure that while good approximations could be made, I'm not sure if the net result of trying to 'generate' odors to mimic the real thing would still find detractors, just as music buffs might sniff at the quality of digital recordings compared with analog recording.

[Amit]

As for 'recreating' odors by mixing and matching chemicals, I'm sure that while good approximations could be made, I'm not sure if the net result of trying to 'generate' odors to mimic the real thing would still find detractors

Not according to the book Fast Food Nation and not according to Eric Schlosser's experience at some chemical labs that are producing food additives to bring out the smell and taste, without any way to tell the difference between the real and the artificial.

[Amit]

IIRC he mentioned that in the lab, when a test tube was uncorked, the atoms of vapor that escaped were enough to evoke a very strong memory of meat (I forget which) sizzling on a grill and the taste of it. Or something along those lines - sorry, read the book a long time ago, so paraphrasing.

[Sujatha]

Amit, do you seriously think that Fruit gushers with strawberry flavor taste like real strawberries? Or that grape Koolaid tastes like real grape juice? An artful mix of esters might fool some but not all.
Another example would be the care that goes into making the composition of infant formula try to mimic that of human milk, but very often, an infant being weaned from human milk to formula will scream bloody murder at the attempted substitution. There are still unidentified compounds, flavors, scents or others that go into one that are not found in the artificial version. The same, very likely, applies to the science of olfactory foolery.

[Amit]

Sujatha, I haven't tried food gushers and I stay away from crap like that masquerading as food - where 'Strawberry' is in big letters and you have to look real close to find a tiny, disguised 'flavored' next to it, with little to no strawberry content listed in the list of ingredients. :-)
I'm very particular about food, especially in the US.

You're right that some foods will probably be more difficult than others to imitate, but I personally know people who love crap like that, and I've seen 1-2 year olds in public eating and drinking such flavored food! (Get them hooked early.) Maybe they never tasted real, fresh strawberries, so they wouldn't know the difference. Besides, the research is ongoing to continue making such additives even "better."

[Amit]

That should be fruit gushers. Bah.