Why do we have two nostrils?

Nostrils. Credits: iStock

Here is a question that we certainly don’t ask ourselves every day! Just like the eyes and ears, the organ of smell operates in twos, and this is no accident.

Human beings have two eyes and two ears, but only one nose, which has two nostrils. While a pair of eyes allows us to view the world in 3D, and two ears enable us to localise sound, it appears that both nostrils are not sensitive to the same odours.

Firstly, we need to be aware that the left nostril shares information with the left hemisphere in the brain, and the right nostril links up with the right hemisphere. The right hemisphere deals more with emotions and spatial awareness, while the left hemisphere is more concerned with language. All in all, the right hemisphere deals with the affective or emotional aspect of smell, and the left hemisphere is in charge of identifying it.

The nose has a surprising functionality: there is an alternate cycle of activity between the two nostrils! In fact, we switch between the nostrils around once an hour, changing the “main nostril” on a regular basis, breathing more through one than the other at any given time. Considering the functions of the left and right hemispheres, you could imagine the possibility of being able to speak better by blocking the right nostril, and improving your spatial awareness by obstructing the left nostril!

This duality is omnipresent in terms of respiration: at any given time, one of the two nostrils is open wide, while the other is barely open, due to swelling of the mucous membranes. Our olfactory abilities are therefore not stable, as explained earlier, which translates into the notion of olfactory inequality. Quebecois researcher Daphnée Poupon presented her research at the 84th congress of the Francophone association for knowledge (ACFAS) in 2016, highlighting the fact that every human being has a “strong nostril”.

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