“Humans smell in stereo” [new study]

Can we smell in ‘stereo’? Recent experiments performed at the University of Chinese Academy of Sciences in Beijing suggest that, to some extent, in some circumstances, the answer could be ‘yes’ – and, moreover, this stereo sense may be a navigational aid. The research team write that :

“The human nose, the most protruding part of the face, bears two nostrils that are separated by the nasal septum and inspire air from nonoverlapping regions (roughly 3.5 cm apart) in space. Theoretically, this provides a computational advantage to localize odor sources as compared with sampling at one point in space.”

With the help of participants using the apparatus shown in the diagram, which dispensed various concentrations of phenylethyl alcohol (a rose-like odorant) and vanillin (a vanilla-like odorant), the experimenters were able to determine that :

[…] a moderate binaral intensity disparity produces a subliminal directional cue that reliably modulates the perception of self-motion independent of trigeminal activity or nasal cycle. Put differently, humans smell in stereo and utilize olfactory stereo cues in the determination of heading direction, despite that they are not verbally aware of such cues.”

Furthermore :

“[…] a moderate internostril difference in odor intensity consistently biases recipients’ perceived direction of self-motion toward the higher-concentration side, despite that they cannot report which nostril smells a stronger odor. The findings indicate that humans have a stereo sense of smell that subconsciously guides navigation.”

See: Humans navigate with stereo olfaction PNAS, June 22nd, 2020,

[ Research research by Martin Gardiner ]