A scientist sniffs out the world of dogs

Dogs may be man’s best friends, but how much do we actually know about our beloved pets? Alexandra Horowitz, professor of cognitive science at Barnard College and author of Being a Dog: Following the Dog into a World of Smell, joins Hari Sreenivasan to discuss how she examines our four-legged friends by studying the complexities of their noses.


Dogs may be man's best friends, but how much do we actually know about our beloved pets?

Alexandra Horowitz, professor of cognitive science at Barnard College and author of 'Being a Dog: Following the Dog Into a World of Smell,' examines our four-legged friends by studying the complexities of their noses.

She joins us now.

How much more powerful is a dog's nose than our own noses?

I mean, we know that they can smell better, but give us the actual fact.

Right. It's tricky to make a numerical estimation.

We know that it's many, exponentially, times better, with many odorants.

So, we make estimates based on things like the number of olfactory receptor cells they have in their nose, the number of cells that are there in their nose to grab odors.

All dogs have hundreds of millions more receptor cells than humans do.

So that probably equals an ability to detect a minute amount of what we are.

And we see that in their behavior.

Sure. And is there some structural difference in a dog's nose, compared to ours?

Well, the whole nose is kind of designed, on the dog, to race odors through the nose and to the brain.

So the long nose is full of bones that hurry up air, warm and humidify the air.

In the back of their nose, they have a space where the odors can kind of linger.

It's called the olfactory recess.

We don't have anything like that.

They have all those hundreds of millions of olfactory cells, and then there's more of their brain committed to determining what the odor is.

So you looked at this almost at a study level.

What did you look at?

I've looked at a lot of levels of behavior because we can't ask the dog, you know, what do they perceive.

My interest is in looking at their behavior and trying to tell what they could perceive.

Now, there's research looking at how small an amount of TNT or other explosive is there.

My interest is more on the order of, 'Do they recognize themselves through their smells?

Can they determine quantity of a food item by smell alone?'

Things like that.

So can they recognize each other through smells?

It looks like they are recognizing not only each other but that they know their own smell and they know when something has changed about their smell.

This is sort of analogous to looking in the mirror and noticing that something's out of sort about your appearance or that there's spinach between your teeth or something.

Can they look in a mirror and see if there's something out of sorts?

They see in mirrors.

They can use a mirror as tools, but there's no evidence that they're using them to kind of guide their own grooming behavior the way we do, but then dogs are not groomers, so we wouldn't expect them to.

So instead I look at, you know, what's their smell.

Do they notice when their smell is different?

Because they're living in an olfactory world, not in a visual world like we are.

So does their smell give them a sense of self similar to how we look in a mirror and say, 'Okay, that is the external vision of myself'?


That's my sense, right?

And owners might behaviorally note this just taking their dog for a walk.

If their dog is peeing someplace, which is leaving information about themselves, they later don't go and investigate that smell, usually.

They're not going to see who that is.

They know who it is.

It's themselves.

They go and investigate other scents of other dogs who have been by.

When you looked at this, were you surprised by the results?

I was delighted by the results.

I was delighted to see that they might have an analogous sense of self in olfaction as in vision.

We've seen examples of dogs, of course, at airports trying to sniff out dangerous substances.

We've also seen dogs that have an ability to, I guess, figure out if prostate cancer exists just by looking at urine -- or cancers.

I mean, it's a really wide range of things.

How is it possible for them to be able to sort all of these categories?

Is it just about what's in their brain and that they can slice and dice?

It's like asking how can we see everything that we see in front of us, right?

At some level, we have experience.

We come with a visual system.

We have experience learning about what different objects are and naming them, so kind of organizing the visual percepts.

They have a rich olfactory percept, and when we tell a dog who we want to train to be an explosives-detection dog, 'When you smell this substance, I want you to alert for me,' they're already smelling it.

They don't have to learn to smell it.

It's part of their olfactory percept.

They just then learn that that's something that the humans want to know about, and they tell us.

When you were writing this book, what was the most surprising thing that a dog could smell that you figured out?

What I loved were the scat-detection dogs.

So there are actually wildlife researchers now who are trying to take canvases of populations of animals who are hard to find, you know, or over hundreds of thousands of acres.

And they found that they could use dogs to just detect the presence of scat, which gives them their DNA.

And, in fact, there's one dog, Tucker, in Puget Sound, who can detect orcas in the water a nautical mile away from the smell of their scat, essentially, from the boat, and then direct the researchers to where the orca is.

[ Laughing ] That's amazing.

It is kind of amazing.

It's mind-boggling, and I think it's ordinary stuff for dogs.

You know, one of the things you also mention in the book is about how we can actually train our sense of smell a lot better, that we're -- even though we don't have as many receptors as a dog does, we're not using them anywhere close to our capacity.

You know, we have a perfectly good sense of smell, and we know that because we taste food.

Most of our sense of taste is entirely because we smell.

In other words, we're smelling through the back of our nose instead of through the nostrils.

So we have all those receptors.

If you have a cold, you might not taste food, right?

And that's 'cause the receptors are blocked.

And I thought, 'Well, let's try to imaginatively leap into what it might be like to be a dog by starting to sniff more things myself.'

And that's the first thing we have to do, which we don't do.

I mean, we just have an aversion to putting our nose up to a substance and smelling it.

We find that funny or silly or foul.

And once you start doing that, you realize, 'Oh, actually I can detect it.'

Everything has an odor.

Everything has an odor.

And so there is this level of richness of the environment that you get a little peak into once you start sniffing.

Sense of smell is such kind of a powerful trigger.

Like, when you say, 'Garbage in New York on a hot summer day,' I just -- there's a vision that I have in my head, right?

Or, for me, it's rain falling on sort of fresh tarmac or a book, frankly.

At this point, [Chuckles] that's becoming something of a relic in the past, right?

But opening an old book, there's a certain smell that you get.

But it's really interesting how connected it is to sense memory and all these other senses.

It's a great trigger.


I mean, people like to say that smell is the quickest route to the brain because there really is just one neuron from the back of the nose, where the olfactory receptor cells are, and the olfactory lobe inside the brain.

And so, at some level, yeah, there does seem to be a more emotive, maybe an often unconscious connection that's made with something visceral, and we have all these great smell memories, right?

I ask people for their smell memories, and suddenly they're back in their grandmother's house when they were five and they're in the attic and the feeling of being that age at that time, with those people.

I'm surprised that, given that we have this often positive -- or at least very emotional connection with smell -- that we aren't intentionally smelling more, that we neglect to smell.

Alexandra Horowitz from the Department of Psychology at Barnard College.

Thanks so much.

Thanks very much.