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Understanding Our Perception Of Smell
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Prof. Murray
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Sep 21, 2007 08:44 PDT
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Understanding Our Perception Of Smell
21 Sep 2007
What makes one smell pleasant and another odious? Is there something in
the chemistry of a substance that can serve to predict how we will
perceive its smell? Scientists at the Weizmann Institute of Science and
the University of California at Berkeley have now discovered that there
is, indeed, such a link, and knowing the molecular structure of a
substance can help predict whether we will find its smell heavenly or
malodorous.
In sight and hearing, for instance, our perceptions are determined by
the physical properties of waves -- the length of light waves in sight,
and the frequency of sound waves in hearing. But until now, there was no
known physical factor that could explain how our brains sense odors. The
new study, conducted by Prof. Noam Sobel of the Institute's Neurobiology
Department and his colleagues, represents a first step in understanding
the physical laws that underlie our perception of smell. Their results
appeared in the Journal of Neuroscience.
To identify the general principles by which our sense of smell is
organized, the researchers began with a database of 160 different odors
that had been ranked by 150 perfume and smell experts according to a set
of 146 characteristics (sweetish, smoky, musty, etc.). These data were
then analyzed with a statistical program that analyzed the variance in
perception among the smell experts. The scientists found that the data
fell along an axis that describes the 'pleasantness rating' of the odors
-- running from 'sweet' and 'flowery' at one end to 'rancid' and
'sickening' at the other. The same distribution along this axis, they
discovered to their surprise, closely describes the variation in
chemical and physical properties from one substance to another. From
this, the researchers found they could build a model to predict, from
the molecular structure of a substance, how pleasing its smell would be
perceived.
To double check their model, Sobel and his team tested how experimental
subjects assessed 50 odors they had never smelled before for
pleasantness. They found that the ratings of their test subjects fit
closely with the ranking shown by their model. In other words, they were
able to predict the level of pleasantness quite well, even for
unfamiliar smells. They noted that, although preferences for smells are
commonly supposed to be culturally learned, their study showed that the
responses of American subjects, Jewish Israelis and Muslim-Arab Israelis
all fit the model's predictions to the same extent. Sobel: 'Our findings
show that the way we perceive smells is at least partially hard-wired in
the brain. Although there is a certain amount of flexibility, and our
life experience certainly influences our perception of smell, a large
part of our sense of whether an odor is pleasant or unpleasant is due to
a real order in the physical world. Thus, we can now use chemistry to
predict the perception of the smells of new substances.'
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Article adapted by Medical News Today from original press release.
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Prof. Noam Sobel's research is supported by the J and R Foundation.
The Weizmann Institute of Science in Rehovot, Israel, is one of the
world's top-ranking multidisciplinary research institutions. Noted for
its wide-ranging exploration of the natural and exact sciences, the
Institute is home to 2,600 scientists, students, technicians and
supporting staff. Institute research efforts include the search for new
ways of fighting disease and hunger, examining leading questions in
mathematics and computer science, probing the physics of matter and the
universe, creating novel materials and developing new strategies for
protecting the environment.
Source: Yivsam Azgad
Weizmann Institute of Science
Article URL: http://www.medicalnewstoday.com/articles/82977.php
Main News Category: Neurology / Neuroscience
Also Appears In: Ear, Nose and Throat,
James A. Murray
Asst. Prof., Department of Biology
156 Lewis Science Center
University of Central Arkansas
Conway, AR 72035
PH: 501-450-5923
FAX: 501-450-5914
EMAIL: jmur-@mail.uca.edu
http://www.uca.edu/divisions/academic/biology/faculty/jmurray.htm
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