Human Scent Tracking January 30, 2007Posted by Johan in Sensation and Perception.
There is an article by Porter et al in Nature Neuroscience on human scent tracking. This is not the result of some psychophysicist trying to bring Vision and Audition’s neglected little brother Olfaction into the spotlight… Rather, it appears Porter et al were interested in the mechanisms of scent-trail tracking in mammals, and had found that most other animals become quite uncooperative when you try to block one of their nostrils.
Nevertheless, the paper reveals that humans have some fairly surprising scent-tracking capabilities. Two-thirds of their untrained participants could track a 10-metre scent trail through an open field, with all other senses blocked (for a fun example, those with access to Nature will be able to see a video of a typical trial). In a second experiment, four participants received 9 sessions of practice, and tracking velocity doubled. Contrary to what you might think, given how close together the nostrils are, Porter et al found that performance was impaired when participants were made to track with only one nostril, or using a prism device that ensured both nostrils got the same input. This suggests that the input you get into each nostril is actually distinct enough to provide meaningful information.
Incidentally, this surprising olfactory ability wouldn’t have surprised Richard Feynman, who described a similar trick in his semi-autobiography Surely You’re Joking, Mr Feynman. He would smell the wrists of his friends, and found that following this, he could identify their wrists by scent alone, when tested. For a Theoretical Physicist, he sure loved his experiments.
I think the fundamental problem for human scent tracking is that our noses are too far from the ground. In the Porter et al paper, the participants were basically crawling on the ground, hands and knees. Humans are just so painfully slow at moving in this fashion that you’re unlikely to ever catch up with any animal you might want to track this way.