The Differences of Vision Between Humans and Dogs狗的视觉与人类的视觉有何区别

Your eyes pick up color using a type of cell called cones in your retina. The same is true for dogs， though our cones aren’t exactly the same.

“Humans have three types of cones， which enables us to see different shades of red， blue-violet， and green，” says Alison Meindl， a professor at Colorado State University.

“Dogs have two types of cones that pick up blue-violet and yellow shades，” says Lara Sypniewski， a professor of small animal medicine at Oklahoma State University.

This means that dogs see in a similar way to humans who are red-green colorblind. “They don’t see red or green and they see everything in shades of blue and yellow，” says Jay Neitz， PhD， a professor of ophthalmology at the University of Washington.

Humans may have the advantage in color vision， but dogs definitely have us beat in the realm of night vision. “This is because dogs’ eyes have more light-gathering power than ours，” Neitz says.

“A dog’s retina is largely composed of cells called rods， which can sense light， even in very low-light conditions，” says Sypniewski.

人类的眼睛通过视网膜的视锥细胞感知颜色，狗也是如此，但两者的视锥细胞并不完全相同。

美国科罗拉多州立大学教授艾莉森·梅恩德称：“人类有三种视锥细胞，因此我们能够看到不同深浅的红色、蓝紫色和绿色。”

美国俄克拉荷马州立大学小型动物医学教授拉腊·西普尼夫斯基称：“狗有两种视锥细胞，可以分辨蓝紫色和黄色。”

这意味着狗的视觉与红绿色盲的人相似。华盛顿大学眼科教授杰伊·内茨博士称：“狗看不见红色和绿色，但能看到蓝色和黄色。”

人类在色觉方面可能有优势，但狗的夜视能力肯定比人类强。内茨说：“这是因为狗的眼睛比人的眼睛更聚光。”

西普尼夫斯基说：“狗的视网膜主要由视杆细胞组成，即使在光线很弱的情况下，视杆细胞也能感知光线。”

Dogs are especially good at sensing movement. “The increased number of rods in the dogs’ retina also increases their ability to detect motion，” Sypniewski says. This ability can help them detect small prey like squirrels.

Dogs have a wider field of vision than humans. Dogs’ eyes are set slightly farther apart than humans’ eyes， so they can see further to the side in each direction.

Dogs have blurrier long-distance vision than humans. A human with perfect vision has 20/20 vision， while dogs have 20/65 to 20/85. “This means that a dog must be at 20 ft to read a letter that a human with 20/20 vision would be able to read at 65 or 85 ft，” says Sypniewski.

Dogs have trouble seeing things very close up. Dogs can see objects clearly if they’re at least 13 to 20 inches away from their eyes， but if the object is closer， the image may be blurry. Humans can see objects slightly closer—about 10 inches away from the eye.

Dogs may recognize you by your shape and motion. “If your dog recognizes you from a distance， it is not because it can see the details of your face like a human would， but rather because of your shape or the way you move，” Neitz says.

狗特别擅长感知运动。西普尼夫斯基说：“狗的视网膜中视杆细胞数量多，这使得它们观察运动的能力更强。”这种能力可以帮助它们发现像松鼠这类小猎物。

狗的视野比人类更宽。狗的眼间距比人的稍远，因此狗能看到的两侧范围更广。

狗的远距离视力比人类更模糊。拥有完美视力的人类有20/20的视力，而狗有20/65至20/85的视力。“这意味着一个拥有20/20视力的人在65或85英尺（约20或26米）处能看到的字，狗必须在20英尺（约6米）处才能看见。”西普尼夫斯基说道。

狗看不清离自己很近的事物。当物体距离眼睛至少13到20英寸（约0.3到0.5米）远时，狗才能看清楚，但如果物体更近，眼中的图像可能就会模糊不清。人类可以看到更近的物体——大约10英寸（约0.25米）远。

狗可以通过人的身形和动作识别主人。内茨说：“如果你的狗能从远处认出你，那不是因为它能像人类一样看清楚你的脸，而是因为认出了你的身形或走路的方式。”

Word Bank

retina /'retɪnə/ （复数retinas/retinae） n. 视网膜

realm /relm/ n. 领域；场所

prey /preɪ/ n. 猎物

The lion will often watch over its prey for hours.

blurry /'blɜːri/ （blurrier为其比较级） adj.  模糊不清的