Which animals are smart? Your answer may bedogs or elephants. Now one more animal can be added to the list: the sheep.

    Scientists said that sheep could be trainedto recognize (辨认) familiar (熟悉的) human faces, the BBC reported.

    Before testing, scientists let the sheeptake a look at the pictures of four famous people, including former (先前的) US President Barack Obama and British actress Emma Watson. Thenthe sheep went into a room with two computer screens. One screen showed afamous person and the second screen showed a random (随机的) person. The sheep usually walked toward the screen with the famousperson.

    After discovering the animals' ability torecognize famous people, scientists gave them a new task. They wanted to seewhether the farm animals could correctly recognize the same people fromdifferent directions. The animals were still able to recognize them, thoughthey were a bit slower to recognize the pictures than before.

    Finally, the researchers wanted to know ifthe sheep could recognize their trainers from a photo. Photos of their trainerswere shown on screens with some unfamiliar faces. They weren't given anytraining, but the sheep could recognize their trainers.

    The results show that the animals' face-recognitionabilities are similar to those of monkeys and humans.

    The researchers said it might beinteresting in the future to find out whether sheep could recognize differentexpressions on people's faces.