英文阅读：狗能识别颜色吗?

英语自学网

　　狗是人类最好的朋友,千百年来,他们和人类相依相存。狗鼻子的灵敏度比人类高上一千倍，不幸的是，狗却分辨不出颜色。这是为什么呢?就让下面这篇文章来告诉你吧。
        　　Man's best friend is colorblind, but, fortunately, his survival does not
depend upon the ability to see colors. His keen sense of smell compensates for
his inability to see colors, and enables him to differentiate between
things.
        　　Extensive scientific testing on dogs supports the conclusion that they live
in a colorless world. The testing done primarily focussed on the dogs' responses
to colors for food. Dogs could not tell the difference between one color, a
signal for food, and other colors, that were not for food. Similar tests
conducted on cats produced similar results, which led scientists to conclude
that they, too, are colorblind and live in a gray world.
        　　The inability of most animals to see colors, from an evolutionary
standpoint, is quite simple to understand. Many colorblind animals have
dull-colored coats, hunt for food in the dark of night, or graze in the dim
twilight hours. Their other senses have developed to the point where the lack of
color vision in no way impairs them. For them, life in a colorless world is
neither a handicap, nor a threat to their survival.
        　　The only animals, other than man, scientists can conclusively say have
color vision are monkeys and apes. Both can be trained to open a colored door,
behind which is food, and man can be trained to open a refrigerator door of any
color!