Humans navigate with stereo olfaction

Significance The human brain exploits subtle differences between the inputs to the paired eyes and ears to construct three-dimensional experiences and navigate the environment. Whether and how it does so for olfaction is unclear, although humans also have two separate nasal passages that simultaneously sample from nonoverlapping regions in space. Here, we demonstrate that 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.