For those who study the development of intelligence（智力）in the animal world, self-awareness is an important measurement. An animal that is aware（意识）of itself has a high
level of intelligence.
Awareness can be tested by studying whether the animal recognizes itself in the mirror, that is, its own reflected image（反射出的影像）．Many animals fail this exercise bitterly, paying very little attention to the reflected image. Only humans, and some intelligent animals like apes and dolphins, have been shown to recognize that the image in the mirror is of themselves.
Now another animal has joined the club. In the Proceedings of the National Academy of Sciences, researchers report that an Asian elephant has passed the mirror self-reflection test. "We thought that elephants were the next important animal," said Diana Reiss of the Wildlife Conservation Society, an author of the study with Joshua M. Plotnik and Fans B．M. de Waal of Emory University. With their large brains, Reiss said, elephants "seemed like cousins to apes and
