You can see the color white; you can hear white noise. Now, Weizmann Institute researchers show that you can also smell a white odor. Their research findings appear today in the Proceedings of the National Academy of Sciences (PNAS).
The white we see is actually a mixture of light waves of different wavelengths. In a similar manner, the hum we call white noise is made of a combination of assorted sound frequencies. In either case, to be perceived as white, a stimulus must meet two conditions: The mix that produces them must span the range of our perception; and each component must be present at the exact same intensity. Could both of these conditions be met with odors, so as to produce a white smell? That question has remained unanswered, until now, in part due to such technical difficulties as getting the intensities of all the scents to be identical.
A research team in the Neurobiology Department, led by research student Tali Weiss and Dr. Kobi Snitz, both in the group of Prof. Noam Sobel, decided to take up the challenge. They began with 86 different pure scents (each made of a single type of odor molecule) spanning the entire "smell map," diluted them to obtain similar intensities and then created blends. Each blend contained a different mixture of odors from various parts of the smell map. These blends were then presented in pairs to volunteers, who were asked to compare the two scent-blends.
The team discovered that the more odors that were blended together in the paired mixtures, the more the subjects tended to rate them as similar – even though the two shared no common components. Blends that each contained 30 different odors or more were thought to be almost identical.
The researchers then created a number of such odor blends, giving them a nonsense name: Laurax. Once the subjects were exposed to one of the Laurax mixes and became accustomed to the smell, they were exposed to new blends – mixtures they had not previously smelled. They also called some of these new blends "Laurax," but only if those contained 30 or more odors and these encompassed the range of possible smells. In contrast, mixtures made of 20 scents or fewer were not referred to as Laurax. In other words, Laurax was a white smell. In a follow-up experiment, volunteers described it as being neutral – not pleasant, but not unpleasant.
"On the one hand," says Sobel, "The findings expand the concept of 'white' beyond the familiar sight and sound. On the other, they touch on the most basic principles underlying our sense of smell, and these raise some issues with the conventional wisdom on the subject." The most widely accepted view, for instance, describes the sense of smell as a sort of machine that detects odor molecules. But the Weizmann study implies that our smell systems perceive whole scents, rather than the individual odors they comprise.
Weizmann Institute of Science: http://www.weizmann.ac.il
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Researchers would use cohort of 1 million Americans pooled from smaller studies to study disease-gene links, improve personalized medicine
Some people have non-human neighbors of the usual, inspiring kind: Bald eagles and bears, sea lions and salamanders, the sort of creatures found in nature documentaries intoned by deep-voiced narrators who plead on our planet's behalf. But I live in New York City. The star of this show, a charismatic megafauna of my own particular wilderness, is none other than the rat — and what science is teaching us may change how we think of this oft-reviled creature, and maybe even ourselves.
An Oregon company has developed a high-tech process for turning sewage into pure drinking water. Now it's asking the state for permission to give its recycled water to a group of home brewers.
Skull cap of Homo sapiens found in Israeli cave hints at time and place of cross-species mingling
Is there a conscious generosity in how ravens or bats share food, or monkeys or elephants save others, or is it simply the selfish instinct of group survival?
DNA research into early canine remains also raises clues about migration patterns of ancient humans
Research on 85 families finds less than a third of siblings with autism carry the same genetic risk, and in nearly 70% of cases known contributory mutations do not overlap
Flanked by curious fish and tended by a diver, these coral nurseries off the coast of the Florida Keys are being grown as transplants for damaged reefs
If we could turn back the clock millions of years, would animals evolve in the same way? Genome data suggests that their options would be limited
Ah, motherhood. I don’t know anything about it, but I heard there’s a lot of, like, sacrifice and stuff. Not only do you have to bring the brat into the world, but then you have to feed it for at least 18 years or you get in big trouble. That’s a lot of pressure.