If you ever get the impression that your dog can “tell” whether you look content or annoyed, you may be onto something. Dogs may indeed be able to distinguish between happy and angry human faces, according to a new study.

如果你有这样的印象，你的狗可以“分辨”出你看上去高兴还是生气，那你可能觉得是重大发现。根据一项新的研究，狗可能确实能够区分人类快乐和愤怒的面孔。

Researchers trained a group of 11 dogs to distinguish between images (图像) of the same person making either a happy or an angry face. During the training stage, each dog was shown only the upper half or the lower half of the person’s face. The researchers then tested the dogs’ ability to distinguish between human facial expressions by showing them the other half of the person’s face or images totally different from the ones used in training. The researchers found that the dogs were able to pick the angry or happy face by touching a picture of it with their noses more often than one would expect by random chance.

研究人员对11只狗进行了训练，让它们区分由同一个人的笑脸或怒容组成的不同画面。在训练阶段，每只狗仅让它看到人脸的上半部分或下半部分。然后，研究人员通过展示人脸的另一半或与训练中使用的完全不同的图像来测试狗区分人类面部表情的能力。研究人员发现，狗能够通过用鼻子触摸照片来挑选出愤怒或快乐的面孔，高于人们预期的狗随机挑选的次数。

The study showed the animals had figured out how to apply what they learned about human faces during training to new faces in the testing stage. “We can rule out that the dogs simply distinguish between the pictures based on a simple cue, such as the sight of teeth,” said study author Corsin Muller. “Instead, our results suggest that the successful dogs realized that a smiling mouth means the same thing as smiling eyes, and the same rule applies to an angry mouth having the same meaning as angry eyes.”

研究表明，这些动物已经弄明白了如何将它们在训练中学到的关于人脸的知识应用到测试阶段的新面孔上。研究报告的作者科辛·穆勒说:“我们可以排除狗只是根据简单的线索(比如看到牙齿)来区分图片的可能性。”“相反，我们的研究结果表明，成功的狗意识到微笑的嘴和微笑的眼睛是一回事，同样的规则，愤怒的嘴和愤怒的眼睛也是同样的意思。”

“With our study, we think we can now confidently conclude that at least some dogs can distinguish human facial expressions,” Muller told Live Science.

穆勒告诉“趣味科学网”：“根据我们的研究，我们现在可以自信地得出结论，至少有些狗能区分人类的面部表情。”

At this point, it is not clear why dogs seem to be equipped with the ability to recognize different facial expressions in humans. “To us, the most likely explanation appears to be that the basis lies in their living with humans, which gives them a lot of exposure to human facial expressions,” and this exposure has provided them with many chances to learn to distinguish between them, Muller said.

目前，我们还不清楚为什么狗似乎具有识别人类不同面部表情的能力。穆勒说:“对我们来说，最可能的解释似乎是，其存在的基础在于它们与人类生活在一起，这让它们经常接触人类的面部表情，”而这种接触也为它们提供了很多学习区分人类表情的机会。