Human navigation relies on inputs to our paired eyes and ears. Although we also have two nasal passages, there has been little empirical indication that internostril differences yield directionality in human olfaction without involving the trigeminal system. By using optic flow that captures the pattern of apparent motion of surface elements in a visual scene, we demonstrate through formal psychophysical testing that a moderate binaral concentration disparity of a nontrigeminal odorant consistently biases recipients’ perceived direction of self-motion toward the higher-concentration side, despite that they cannot verbalize which nostril smells a stronger odor. We further show that the effect depends on the internostril ratio of odor concentrations and not the numeric difference in concentration between the two nostrils. Taken together, our findings provide behavioral evidence that humans smell in stereo and subconsciously utilize stereo olfactory cues in spatial navigation.

人类导航依赖于我们成对的眼睛和耳朵的输入。尽管我们也有两个鼻腔通道，但几乎没有经验表明，鼻孔间的差异会在不涉及三叉神经系统的情况下在人类嗅觉中产生方向性。通过使用光学流捕获视觉场景中表面元素的明显运动模式，我们通过正式的心理物理测试证明，非三叉戟气味剂的中度双耳浓度差异始终使接收者的自我运动方向偏向较高浓度。方面，尽管它们无法说出哪种鼻孔闻起来更浓。我们进一步表明，效果取决于气味浓度的鼻孔间比率，而不取决于两个鼻孔间浓度的数值差异。在一起