“The act of smelling something, anything, is remarkably like the act of thinking itself,” the great science storyteller Lewis Thomas wrote in his beautiful 1985 meditation on the poetics of smell as a mode of knowledge. But, like the conditioned consciousness out of which our thoughts arise, our olfactory perception is beholden to our cognitive, cultural, and biological limitations. The 438 cubic feet of air we inhale each day are loaded with an extraordinary richness of information, but we are able to access and decipher only a fraction. And yet we know, on some deep creaturely level, just how powerful and enlivening the world of smell is, how intimately connected with our ability to savor life. “Get a life in which you notice the smell of salt water pushing itself on a breeze over the dunes,” Anna Quindlen advised in her indispensable Short Guide to a Happy Life — but the noticing eclipses the getting, for the salt water breeze is lost on any life devoid of this sensorial perception.

Dogs, who “see” the world through smell, can teach us a great deal about that springlike sensorial aliveness which E.E. Cummings termed “smelloftheworld.” So argues cognitive scientist and writer Alexandra Horowitz, director of the Dog Cognition Lab at Barnard College, in Being a Dog: Following the Dog Into a World of Smell (public library) — a fascinating tour of what Horowitz calls the “surprising and sometimes alarming feats of olfactory perception” that dogs perform daily, and what they can teach us about swinging open the doors of our own perception by relearning some of our long-lost olfactory skills that grant us access to hidden layers of reality.

The book is a natural extension of Horowitz’s two previous books, exploring the subjective reality of the dog and how our human perceptions shape our own subjective reality. She writes:

I am besotted with dogs, and to know a dog is to be interested in what it’s like to be a dog. And that all begins with the nose.

What the dog sees and knows comes through his nose, and the information that every dog — the tracking dog, of course, but also the dog lying next to you, snoring, on the couch — has about the world based on smell is unthinkably rich. It is rich in a way we humans once knew about, once acted on, but have since neglected.

Dogs have become our olfactory informants — sensory prosthetics of sorts, capable of detecting what our creaturely capacities cannot: drugs, bombs, storms, sicknesses of body and spirit. But they are also, Horowitz notes, our teachers in recovering some of those capacities long-ago relinquished to evolution:

By following the dog’s lead, we can learn from him about what we are missing — some of which is beyond our ability to sense, and some of which we simply need a guide to see. The world abounds with aromas, but we are spectacle-less. The dog can serve as our spectacles.

In so doing, we may also see how to return to that perhaps more primal, so-called animal state of knowledge about ourselves and the world that we have forgotten in a culture wrought of technology and lab tests. To follow animals is to become more attuned to our own existence. To follow dogs is to begin to apprehend the experience of our silent, loyal partners through our days.

The way dogs use smell offers clues to their very consciousness and the profound ways in which it differs from ours. Horowitz considers one central question of consciousness — “self-recognition,” or having a sense of oneself and recognizing oneself as distinct from others. The common method scientists use to test for self-recognition, known as the mirror mark test, is ingeniously simple: A visible mark is made on the subject’s face or body to see if they attempt to remove it when they face the mirror. In humans, self-recognition occurs around the age of eighteen months, so young infants don’t reach for the mark and thus fail the test.

More than seven decades after pioneering philosopher Susanne Langer wrote about how our questions shape our answers and direct our orientation of mind, Horowitz points to the flaw of using this human-centric method to test for self-recognition in other animals:

Chimpanzees pass (after being inked on their foreheads), an elephant named Happy passed (when an X of tape was placed above her eye), and captive dolphins pass (by doing bodily convolutions in order to examine the ink marks in reflective glass).

Dogs do not. Imagine showing your dog the mirror when his face is covered with stickers. He will, no doubt, express indifference. What looks foolish to us is not of moment to him. But this is not sufficient evidence to say that dogs fail the test and thus have no sense of themselves. For one thing, dogs do not groom themselves (like primates) and show little concern for maintenance of appearance. So they are simply unlikely to want to correct an errant mark on their faces. Neither are they visually oriented as primates are. While the mirror test is appropriate for some species, this paradigm offers challenges for dogs, who show little interest in a mirror.

In a testament to the fact that cognitive scientists are — perhaps because they need to be — among the most inventive of experimentalists, Horowitz describes the clever method she and her team half-discovered, half-devised to bypass the species-bias problem of the mirror mark test:

Some research hints that dogs might nonetheless be able to pass such a test, if a kind of olfactory mirror were designed: something that smelled like them, but was a small bit different. While walking his dog in the winter in the foothills of Colorado, researcher (and my colleague) Dr. Marc Bekoff wondered if every “yellow spot” in the snow was equally interesting to his dog Jethro. Bekoff began carefully noting where his dog peed and where his dog sniffed. He even ported some yellowed snow to new locations to see what happened. He found that Jethro avoided smelling his own urine but smelled others’: a kind of recognition of himself, written in the snow.

To test for this, Horowitz and her team created a version of the classic self-recognition test based on olfactory rather than visual reflection, using a canister exuding odor instead of a mirror. What they found was that dogs did recognize the “scent-image” of themselves from that of other dogs — that is, they demonstrated the seemingly simple yet cognitively complex ability of self-recognition.

Among the misconceptions and mysteries Horowitz illuminates — including how dogs discern each other’s age by smelling the biochemistry of the metabolic process and why male dogs sniff the hind-sides of other dogs, but females and wolves go for the face — is the question of how dogs actually use “scent-marking”: not in the way common lore perpetuates. Horowitz explains:

Here’s a surprise: in contrast to these other marking animals, domestic dogs do not mark territorially. Yes, you read that right. Dogs are not “marking their territory.” How do we know this? Simply by looking at where dogs do — and do not — pee. Owned dogs do not mark the periphery of their homes. The apartment-living dog does not pee along the walls and threshold… When living in fenced suburban yards, dogs do not assiduously line the border of the property with pee. Research in India on the massive free-ranging dog population there — stray dogs who actually might have home territories at risk of being wandered into by others — found that they, too, rarely mark on the boundary of a territory. Dogs walked along shared paths and parks could not verily consider these areas their “territories,” given the occasionalness of their occupying them — and indeed they show no accompanying behaviors that would indicate that dogs feel that a path is “theirs.”

[…]

Most likely, it is social information being left.

To decode what messages that information actually contains, Horowitz applied to the New York City Parks Department and proceeded to perform a series of clever experiments and observations in public parks. What she learned about the astonishing olfactory universe of dogs profoundly altered her own experience of the world. In a lyrical passage that crystallizes the invitation at the heart of the book, she writes:

A summer trip in the car is not complete without notes of gasoline, cut grass, honeysuckle, warmed vinyl, sunscreen, overheated-dog breath, and wet sandals, stirred by wind from the open windows or wafting up from the floorboards.

I smell a thunderstorm approaching on my last visit to Colorado, the home of my family during my childhood, when I come to help clean out the house after my father’s death. The watery, fresh smell of sea air comes, I now know, from ozone carried down from higher altitudes on the winds of a storm. It is also the odor of the city when I emerge after swimming, the receptors pinging chlorine! silent for a long enough moment for me to smell the world in its absence.

I smell gin on the man who sits next to me in 10C.

I smell the acrid, lingering piles of freshly turned, festering wood chips on the other side of the park.

I see two people with a dog; then a second later smell that dog’s poo, which must’ve recently been deposited in a trash bin.

I smell the art room at kindergarten before seeing it.

I smell every book I open.

[…]

I will never smell as a dog does. I accept it. It is dogs’ difference I celebrate — and their ways of smelling — their very noses — are different. Quiet distillers of a world that we have stood up from and forgotten.

Complement the fantastically fascinating Being a Dog with Diane Ackerman on the science of smell, then revisit Horowitz on the art of looking.