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    White Light, White Noise, White Odor?
    By News Staff | November 26th 2012 12:00 PM | Print | E-mail | Track Comments

    You can see the color white and you can hear white noise but you can also smell a white odor, says new research. 

    When we see white, we are seeing a mixture of light waves of different wavelengths. The hum we call white noise is a combination of assorted sound frequencies but in both cases 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.

    Both of these conditions can be met with odors, so as to produce a white smell - it just involves technical difficulties, like getting the intensities of all the scents to be identical. 

    A research team in the Neurobiology Department at
    Weizmann Institute of Science began with 86 different pure scents, each made of a single type of odor molecule and spanning the entire "smell map," and then diluted them to obtain similar intensities.  Then they 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.

    Prof. Noam Sobel says, "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 study implies that our smell systems perceive whole scents, rather than the individual odors they comprise. 


     Published in the Proceedings of the National Academy of Sciences (PNAS).