Smelling in Stereo: Human Sense Detailed in Study Just as they hear in stereo, humans also smell in stereo, according to a new report. Researchers at the University of California, Berkeley, found that humans use both nostrils to determine where a smell is coming from, much like we use our two ears to find where sound is coming from.

Smelling in Stereo: Human Sense Detailed in Study

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.


And I'm Michele Norris.

Here's a story to file under the category: who knew?

In this case, who knew that humans smell in stereo, using both nostrils to figure out where in space a scent is coming from? To compare this with hearing, it's a bit like the way humans use both ears to figure out where a sound is coming from, and to compare it with vision.

Professor NOAM SOBEL (University of California, Berkeley): It's like that each nostril was looking at a different area or different part of the world.

NORRIS: That's Noam Sobel, associate professor of neuroscience and psychology at the University of California, Berkeley. He and graduate student Jess Porter are authors of a new study in the journal, Nature Neuroscience. Sobel and Porter proved that humans smell in stereo by first asking their subjects, Berkeley undergraduates, to sniff out a 10-meter long scent trail through a field.

After finding out that most could follow the trail, they conducted two experiments to see whether the subjects were in fact using both nostrils to locate the odors.

Professor SOBEL: In one experiment, we actually blocked one of their nostrils. So we just taped it shut. And with one nostril, they were both slower and less accurate.

The second test we did addressed some concerns that were related to the first test, I'll try and simply state one of those concerns. If we blocked one of your nostrils, you're just getting less overall information. So we devised these Teflon-built devices that fit into your nose, and what they do is combine both nostrils into one nostril in the center of your nose. And once again, people performed worse with this one nostril versus a similar device with two nostrils.

So the combination of these experiments led us to conclude that comparing information across the nostrils is helpful in performing this task.

NORRIS: Jess Porter, you were the lead researcher on this. Could you paint a picture for me, what did the subjects actually look like - down on all fours, noses to the ground?

Ms. JESS PORTER: That's exactly right. They're on all fours and they have to bring their noses very close to the grass, and sniff along pretty carefully. So if you look at a person and compare it to a dog, dogs are able to go much faster and it clearly seems to be something that's way easier for them to do.

Our subjects, initially, would take maybe 10, or if we let them, 15 or 20 minutes to go 10 meters across a field. Whereas, a dog could come running by the experiment and immediately, you could tell it knew the whole story it needed, you know, a few seconds to figure things out.

NORRIS: It sounds like in looking at your research that once people got the hang of this that they actually evolved to some degree. There was a sort of this olfactory evolution. They developed techniques to improve their ability to pick up and follow a scent.

Professor SOBEL: Yes. Day after day, they got much more accurate and much faster. We're left wondering if we continue doing this, how good they would get. And what Jess suggested and it seems to be correct is that the limiting or rate limiting factor on that was how fast they could crawl.

NORRIS: So what's the practical effect of this research? Can people do this while standing or sitting or driving in a car? Do they have to literally keep their nose to the ground?

Professor SOBEL: There are two areas where there's practical implications, one, we're using humans here as a model. We're using them as a model to try and understand if mammals in general, use this strategy of comparing across the two nostrils.

The second implication is a more direct one, maybe, is our lab is involved in developing electronic nose devices. These are devices that are an artificial imitation, if you will, of the sense of smell. And the ultimate goal of these devices is to do things like demining. In fact, this is an army-funded project towards demining efforts.

This is not something that's going to happen tomorrow, but that is the ultimate application.

NORRIS: Professor Sobel, Jess Porter, it's been great to talk to both you. Thanks so much.

Professor SOBEL: Thank you very much.

Ms. PORTER: Thank you Michele.

NORRIS: Noam Sobel and Jess Porter from the University of California at Berkeley. You can actually see a video of the human-sniffers at our Web site

Copyright © 2006 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.