For dogs, "smell tells time"

 "…Dogs, as anyone who has ever met one knows, sniff a lot. They are, says Horo­witz, “creatures of the nose.” To help us grasp the magnitude of the difference between the human and the canine olfactory umwelts, she details not only the physical makeup of a dog nose (a beagle nose has 300 million receptor sites, for example, compared with a human being’s six million), but also the mechanics of the canine snout. People have to exhale before we can inhale new air. Dogs do not. They breath in, then their nostrils quiver and pull the air deeper into the nose as well as out through side slits. Specialized photography reveals that the breeze generated by dog exhalation helps to pull more new scent in. In this way, dogs not 

only hold more scent in at once than we can, but also continuously refresh what they smell, without interruption, the way humans can keep 'shifting their gaze to get another look.'

"Dogs do not just detect odors better than we can. This sniffing 'gaze' also gives them a very different experience of the world than our visual one gives us. One of Horowitz’s most startling insights, for me, was how even a dog’s sense of time differs from ours. For dogs, 'smell tells time,' she writes. “Perspective, scale and distance are, after a fashion, in olfaction — but olfaction is fleeting. . . . Odors are less strong over time, so strength indicates newness; weakness, age. The future is smelled on the breeze that brings air from the place you’re headed.' While we mainly look at the present, the dog’s “olfactory window” onto the present is wider than our visual window, 'including not just the scene currently happening, but also a snatch of the just-happened and the up-ahead. The present has a shadow of the past and a ring of the future about it.' Now that’s umwelt.

"A dog’s vision affects its sense of time, too. Dogs have a higher 'flicker fusion rate than we do, which is the rate at which retinal cells can process incoming light, or 'the number of snapshots of the world that the eye takes in every second.' This is one of the reasons dogs respond so well to subtle human facial reactions: 'They pay attention to the slivers of time between our blinks.') It also helps explain those ­eerily accurate balletic leaps after tennis balls and Frisbees, but Horowitz lets us see the implications beyond our human-centric fascination with our pets. This is more than a game of fetch; it is a profound, existential realization: 'One could say that dogs see the world faster than we do, but what they really do is see just a bit more world in every second.' "

…from: INSIDE OF A DOG: What Dogs See, Smell, and Know by Alexandra Horowitw, reviewed by Cathleeen Schine

(Original drawing by Doug Millison.)