Odor Fatigue

Have you ever noticed a particular scent upon entering a room, and then not noticed it ten minutes later? This is due to olfactory fatigue. The olfactory sense is unique because it relies on mass, not energy to trigger action potentials. Your ears do not "stop" hearing a sound after a certain period of time, nor do your eyes stop seeing something you may be staring at. This is because both the ears and the eyes rely on energy to trigger them, not mass. In the nose, once a molecule has triggered a response, it must be disposed of and this takes time. If a molecule comes along too quickly, there is no place for it on the olfactory hairs, so it cannot be perceived. To avoid olfactory fatigue, rabbits have flaps of skin that open and close within the nostrils. This allows for short, quick sniffs and lets the rabbit "keep in close odor contact with its environment." When we wish to fully perceive a scent, we humans also smell in quick, short sniffs, often moving the source of the smell in front of one nostril then the other. This behavior also prevents odor fatigue. (Stoddard & Whitfield, 1984)

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