阅读理解
Science is proving what pet owners have long believed: Dogs understand what we're feeling. Especially, dogs can recognize(识别) the difference between a happy and an angry human face, a study published Thursday in Current Biology suggests.
It's the first research to show that dogs are sensitive (敏感) to our facial expressions, says the author Ludwig Huber at the University of Veterinary Medicine, Vienna.
In the Austrian study, 20 different kinds of pet dogs were taught to play a computer game through a series of exercises. In the first step, the dogs were shown two touch screens, one with a circle and one with a square. Through the exercises, they learned that a treat would appear if they chose the right one.
Eleven of the 20 dogs were able to catch on to rules of the game and make it to the next test, where they were shown photos of happy and angry faces. The dogs were rewarded if they picked certain expression correctly. During the test, the dogs were shown only the upper half or the lower half of a face.
It was easier to teach the dogs to choose a happy expression than an angry one, suggesting the dogs do indeed understand the meaning behind the expression, Huber says.
As a test, the dogs were then presented with: the same half of the faces they saw during the training, but from different people， the other half of the faces used in training， the other half of new faces， the left half of the faces used in training.
In the cases, the dogs chose the right answer 70 to 100 percent of the time.
Dogs who had been trained to recognize an expression of anger or happiness on the upper part of a face could find the same expression when shown only the lower part. Huber says, "The only possible explanation is that they recall from memory of everyday life how a whole human face looks when happy or angry."
Dog owners know their pets not only recognize emotions but also understand the feelings.
轴正方向传播的一列简谐横渡在某时刻的波形图为一正弦曲线，其波速为200 m／s，下列说法中错误的是 （ ）
