Nov 20, 2012

White Noise: The Fragrance

Crossposted from Reflections Journal.

There are a few fun facts that I learned in aromatherapy school. Our sense of smell, or olfaction, is one nerve synapse away from the limbic brain and clicks rapidly through the amygdala and hippocampus. So smells trigger memories and powerful emotional responses. Olfaction does not go through the neocortex, so there are no words that exclusively describe smells. We borrow adjectives from other sensory stimuli to describe them, like colors, sounds, and tastes. For instance, scents can be green, or loud, or fruity. Now comes a newly created scent profile called "white noise."

Another thing I learned in aromatherapy school is that, while this is a fascinating discovery about our sense of smell, the study described here does not constitute aromatherapy. Aromatherapy is the use of pure plant essences and offers numerous therapeutic properties above and beyond the psychoactive effects of scent. The fragrance industry relies heavily on chemically replicated scents and other derivatives of natural essences and I suspect that is the case here as well. Still. Fascinating.

Mixing multiple wavelegths that span the human visual range equally makes white light; mixing multiple frequencies that span the range of human hearing equally makes the whooshing hum of white noise. Neurobiologist Noam Sobel from the Weizmann Institute of Science in Israel and his colleagues wanted to find out whether a similar phenomenon happens with smelling. [7 New Flavors Your Tongue May Taste]

In a series of experiments, they exposed participants to hundreds of equally mixed smells, some containing as few as one compound and others containing up to 43 components. They first had 56 participants compare mixtures of the same number of compounds with one another. For example, a person might compare a 40-compound mixture with a 40-compound mixture, neither of which had any components in common.

This experiment revealed that the more components in a mixture, the worse participants were at telling them apart. A four-component mixture smells less similar to other four-component mixtures than a 43-component mixture smells to other 43-component mixtures.

. . .

In other words, our brains treat smells as a single unit, not as a mixture of compounds to break down, analyze and put back together again. If they didn't, they'd never see mixtures of completely different compounds as smelling the same.

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