How does a dog see the world?

mother nature network

SATURDAY, AUGUST 10, 2013  

How does a dog see the world?

Houndsight isn't 20/20
Not much gets past a dog's nose, but what about those eyes? What do dogs see when they gaze soulfully up at people or ogle birds and squirrels?

Dogs see in color, despite an old misconception, but their world still doesn't look quite like ours. While human eyes contain three kinds of color-sensing "cone" cells, dogs have just two, leaving them oblivious to red. Their lower visual acuity also makes everything look blurrier.

We may never know what it's like to be a dog — especially without their noses — but search engine Wolfram Alpha helps us guess, offering a dog vision tool that edits photos to mimic canine eyesight. Here are a few examples, republished with permission, in hopes of shedding a little light on man's best friend. (Text: Russell McLendon)

Flowers

To be fair, dogs know more about flowers than this. We often assume other animals share our emphasis on sight, but images can only scratch the surface of a dog's scent-centric existence.


Still, we know they lack the ocular equipment to see red. Dogs may see a bit like people with red-green colorblindness — albeit blurrier, since they have four to eight times less visual acuity than humans. That's roughly 20/75 vision, meaning dogs lose sight of patterns at 20 feet away that most humans could see at 75 feet.

Other dogs

Since dogs can't see red, scientists used to think they use luster more than color as a visual cue. But a recent study disputes that idea, finding color is "more informative than brightness" for a dog comparing two objects that differ in both.

Fur color might therefore help dogs recognize each other from a distance, along with related signals like body size and shape. This chow's reddish coat may seem green to other dogs, but that skewed hue could still help them distinguish it from a Swedish Lapphund down the street — at least until they get close enough for a proper sniff-down.

Humans

Canine communication is big on folded ears, tucked tails and other body language, but pet dogs are also careful students of the human face. Not only can a dog identify its owner's face in a crowd, but it can even tell when a stranger is smiling.

Since President Obama is widely recognizable, our view of this modified image may resemble how dogs see a familiar human face. It's much blurrier than what we see, but that basic amount of visual information still sparks welcome-home frenzies from dogs around the world every day.

Squirrels

Despite their color and acuity issues, dogs are uncanny motion detectors.  A stationary squirrel may blend into the background, but any sudden moves could alert dogs as far as half a mile away.

Canine retinas are packed with light-sensitive "rod" cells, helping them detect slight motion in daylight or darkness. A 1936 study on police dogs found some could identify moving objects from 2,900 feet away, but their range fell to 1,900 feet when the same objects were motionless.

Bacon

Bacon smells great to us, but imagine how it must smell to dogs, who have about 50 times more olfactory receptors, helping make their sense of smell up to 100,000 times stronger. They can also hear it sizzling from four times farther away.

We may end up enjoying it more, though: Not only does bacon look green and blurry to dogs, but they have one-sixth our number of taste buds.