公鸡能辨认出镜子中的自己吗？
The mark test (or “mirror test”) is often seen as a good way to learn if an animal is aware of itself — one sign of how smart an animal is. The list of animals that can recognize themselves in a mirror isn’t long. The skill has mainly been found in animals with large brains, like dolphins, chimpanzees, and elephants. Until recently, only one kind of bird had passed the test.
But some scientists believe the mark test doesn’t work well for all animals. Roosters are a good example. Scientists at the University of Bonn in Germany recently ran the mark test on roosters. They put a pinkish triangle on the chest of the roosters. But when the roosters looked in a mirror, they didn’t seem to notice the mark.
The scientists needed a different way to test whether the roosters could recognize themselves. When there’s danger — like a hawk (鹰) flying above — roosters make loud calls to warn nearby chickens. But roosters only make the cries if other chickens can hear them. If they’re alone, they remain quiet so the hawk won’t see them. The scientists realized that they could use the shadow of a hawk to test whether or not the roosters thought they were alone — even when they could see “another” chicken in a mirror.
First, the scientists let the roosters spend time getting used to being in a closed-in space and having a mirror around. Then, they ran several tests by making a hawk shadow appear above the bird and watching how the rooster reacted. When there was no mirror, the roosters reacted as usual: they called out when they were near another rooster, but remained quiet when they were alone. But when a rooster was in a space where it could see itself in the mirror, it wasn’t fooled into thinking there was another rooster. It remained silent despite the hawk shadow. It did this even if there was a rooster hidden behind the mirror.
The scientists hope their results will encourage other scientists to look for better ways of testing self-recognition in animals. It may turn out that some kinds of animals are more intelligent than people thought.
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