Have you ever heard of the expression “birdbrain”? People use it to talk about someone who is stupid, but crows(渡鸦) prove that this is unfair. Now it has been discovered that crows may understand analogies(类推法).

It was once thought that only humans could understand analogies, which help us to solve problems creatively and make scientific discoveries.

To testthis ability in animals, scientists do RMTS tests. If a pair was AA, for example, then picking BB to match it would be correct.

Monkeys have learnedRMTS, but scientists wanted to know if crows could do it, too. An international team led by Edward Wasserman in the US first trained two crows to match things by color, shape, and number in what is called IMTS, then moved onto RMTS.

For theIMTS test, the birds were put in a cage with a plate that had three cards and two cups in it. The card in the middle was the sample card. The cups on either side were covered with the other two cards: One was the same as the sample（in the color, shape, or number of shapes pictured）, while the other wasn’t. The cup with the card that matched the sample card had some food to eat.

In the second partof the experiment, the birds were tested with RMTS tests. A card with two same-sized circles, for example, meant they should pick the test card with two same-sized squares and not two different-sized circles. The birds did well in the more difficult test and picked the correct card more than three quarters of the time, Science New reports.

Wasserman was surprised that crows were able to solve the problem without any training in RMTS. “What the crows have done is surprising,” he said.