Scientists have long known that humans and animals actively explore the world through movement—by shifting their gaze, turning their heads, or moving their hands. Smell is also an active sense: to better detect an odor, we take short, deliberate “sniffing” breaths. However, it has remained unclear whether the pattern of these sniffing breaths changes depending on the specific smell we perceive.

Researchers from Northwestern University (USA) have now shown for the first time that it does—and very significantly. Their study, published in Nature Human Behavior, demonstrates that the way a person inhales while smelling constantly adjusts to the particular odor and carries detailed information about it.

The authors used the previously collected NEMO dataset: more than 12,000 experiments in which three volunteers inside an MRI scanner inhaled 160 different odors. Such a large dataset was essential because odor-induced changes in breathing can be very subtle. The scientists analyzed the trajectory of the breaths while simultaneously recording brain activity.

Machine learning allowed them to predict which odor a person was smelling from sniffing patterns alone. Each scent produced its own “signature” in the breathing pattern—barely noticeable, yet stable. Key brain regions, especially the amygdala, played a major role in this process.

Interestingly, the amygdala has previously been linked to breathing disturbances in patients with epilepsy.

The study shows that olfaction is a closed-loop system of active perception, much like vision or hearing. Just as the gaze follows an object, the inhale adjusts to the smell.

According to the authors, the next step is to test whether modifying sniffing patterns can change the perception of odors themselves. The scientists also plan to examine how emotions, attention, and the surrounding environment influence breathing and olfaction.