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  • "Hi, Bob."

  • "Morning, Kelly. The tulips looks great."

  • Have you ever wondered how your dog experiences the world?

  • Here's what she sees.

  • Not terribly interesting.

  • But what she smells, that's a totally different story.

  • And it begins at her wonderfully developed nose.

  • As your dog catches the first hints of fresh air, her nose's moist, spongy outside helps capture any scents the breeze carries.

  • The ability to smell separately with each nostril, smelling in stereo, helps to determine the direction of the smell's source,

  • so that within the first few moments of sniffing, the dog starts to become aware of not just what kinds of things are out there but also where they're located.

  • As air enters the nose, a small fold of tissue divides it into two separate folds, one for breathing and one just for smelling.

  • This second airflow enters a region filled with highly specialized olfactory receptor cells, several hundred millions of them, compared to our five million.

  • And unlike our clumsy way of breathing in and out through the same passage, dogs exhale through slits at the side of their nose,

  • creating swirls of air that help draw in new odor molecules and allow odor concentration to build up over mulitple sniffs.

  • But all that impressive nasal architecture wouldn't be much help without something to process the loads of information the nose scoops up.

  • And it turns out that the olfactory system dedicated to processing smells takes up many times more relative brain area in dogs than in humans.

  • All of this allows dogs to distinguish and remember a staggering variety of specific scents at concentrations up to 100 million times less than what our noses can detect.

  • If you can smell a spritz of perfume in a small room, a dog would have no trouble smelling it in an enclosed stadium and distinguishing its ingredients to boot.

  • And everything in the street, every passing person or car, any contents of the neighbor's trash, each type of tree,

  • and all the birds and insects in it has a distinct odor profile telling your dog what it is, where it is, and which direction it's moving in.

  • Besides being much more powerful than ours, a dog's sense of smell can pick up things that can't even be seen at all.

  • A whole separate olfactory system, called the vomeronasal organ, above the roof of the mouth, detects the hormones all animals, including humans, naturally release.

  • It lets dogs identify potential mates, or distinguish between friendly and hostile animals.

  • It alerts them to our various emotional states, and it can even tell them when someone is pregnant or sick.

  • Because olfaction is more primal than other senses, bypassing the thalamus to connect directly to the brain structures involving emotion and instinct,

  • we might even say a dog's perception is more immediate and visceral than ours.

  • But the most amazing thing about your dog's nose is that it can traverse time.

  • The past appears in tracks left by passersby, and by the warmth of a recently parked car or the residue of where you've been and what you've done recently.

  • Landmarks like fire hydrants and trees are aromatic bulletin boards carrying messages of who's been by, what they've been eating, and how they're feeling.

  • And the future is in the breeze, alerting them to something or someone approaching long before you see them.

  • Where we see and hear something at a single moment, a dog smells an entire story from start to finish.

  • In some of the best examples of canine-human collaboration, dogs help us by sharing and reacting to those stories.

  • They can respond with kindness to people in distress, or with aggression to threats because stress and anger manifest as a cloud of hormones recognizable to the dog's nose.

  • With the proper training, they can even alert us to invisible threats ranging from bombs to cancer.

  • As it turns out, humanity's best friend is not one who experiences the same things we do, but one whose incredible nose reveals a whole other world beyond our eyes.

"Hi, Bob."

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B1 US TED-Ed olfactory odor smelling smell breeze

【TED-Ed】How do dogs "see" with their noses? - Alexandra Horowitz

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    稲葉白兎 posted on 2015/03/09
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