Research is now suggesting something dog-lovers have long suspected - man's best friend can tell the difference between our happy and angry faces.

“狗奴”们一直怀疑对汪星人——人类最好的朋友——能够分辨我们快乐和生气的表情，日前一项研究认同了这一点。

Scientists at the Messerli Research Institute's Clever Dog Lab in Vienna trained dogs to associate pictures of happy or angry faces with a reward.

维也纳梅瑟利研究所“聪明狗狗”实验室（Messerli Research Institute's Clever Dog Lab）的科学家们，训练狗狗将笑脸或怒容的图片与奖励联系在一起。

In a subsequent test, the scientists showed the dogs images of human faces they had not seen in their training.

在接下来的测试中，科学家们给狗狗展示了一组它们在训练中从未见过的人脸图像。

This suggested that dogs could spot the difference between the expressions.

测试表明狗可以分辨出表情的不同。

"The main focus [of our research] is the big question of communication," lead researcher Prof Ludwig Huber said.

“（我们研究的）重点在于“交流”这个重大问题，”研究小组负责人路德维格·胡贝尔（Ludwig Huber）教授说。

"How is it that dogs are so adapted to humans, and what's happened during the process of domestication¹?"

“狗是如何适应与人类亲密相处的？在驯养过程中发生了什么？”

The scientists repeatedly showed 20 dogs half pictures - either the lower mouth region or the upper eye area - of happy or angry human faces.

科学家反复向20只狗展示半张人类的笑脸或怒容图片——要么是只有嘴的下半部分，要么是只有眼睛的上半部分。

Half the dogs received a treat when they touched an angry face with their nose. The other half were rewarded for touching² happy faces.

其中一半的狗用鼻子触碰生气表情的图片时，就会得到奖励。另一半则在触碰笑脸时获得奖励。

Just over half the dogs learned the task well enough to be tested, and there were then a number of different tests to find out if they could tell the difference solely³ on the basis of facial expression.

仅有超过一半的狗较好地理解了这一任务，从而有能力接受测试。随后研究人员又进行了系列不同的测试，来证明它们是否能够仅靠面部表情分辨出其中的不同。

"[In one test condition], we showed them new faces - faces they've never seen before," Prof Huber told BBC News.

“（在其中一项测试条件下），我们给狗狗展示新面孔，它们之前从未见过这些人脸，”胡贝尔教授接受英国广播公司采访时说。

"In another, we showed them different parts of the faces."

“另一项测试中，我们给它们看面部的不同部分。”

Showing dogs the opposite half of the face to the half they had learned to recognise in their training, showed they could "transfer their knowledge" of human facial expressions.

研究人员给狗狗们展示它们在训练中所辨认的半张面部图片的另一半，结果表明它们对人类面部表情的知识可以“活学活用”。

"So, for example, in the training, they see the mouth region of the happy face," said Prof Huber, "and they associate that with what the eyes would look like."

“比如，举个例子，在训练中，它们看到了笑脸的嘴部区域，”胡贝尔教授说，“然后它们能将其与看上去对应的眼睛联系起来。”

This study, published in the journal Current Biology, is part of a larger project studying how humans and their canine⁴ companions interact.

这项研究发表在《当代生物》（Current Biology）杂志上，是一项关于人类与狗如何互动的大型研究课题的一部分。

Dr Kun Guo, a psychologist and expert in human-animal interaction from the University of Lincoln, said: "Showing dogs only half of the face and then the other half separately means they can't rely on the shape of the eyes or the mouth - they must have some sort of template in their mind.

林肯大学（University of Lincoln）心理学家及人与动物相互关系专家昆·郭（Kun Guo）博士表示：“先让狗狗看半张脸部图片，然后再看另半张，这就意味着它们不能依靠眼睛或嘴巴的形状来辨别表情——它们的脑海中一定有某种样板。”

"So it looks like they can really discriminate⁵ between happy and angry."

“如此看来，狗确实能区分人是高兴还是生气。”

But, he added, this did not show that dogs understood the meaning of those emotional expressions.

但是，他补充说，这并不能够说明狗懂得那些情绪表情的含义。

Prof Huber agreed but added that the dogs that had had to touch the angry face to be rewarded, in the training, had taken three times as long to learn the task.

胡贝尔教授赞成这一点但又补充说，那些在训练中需触碰生气表情来获得奖励的狗要经过三次尝试才能成功完成任务。

"It seems as if they don't like to touch an angry face," he said.

“看起来就像是它们不喜欢触碰带着怒容的脸一样，”他说。

"So here we have some suggestive evidence that they interpret those pictures, and maybe they really understand an angry face to be something they don't like."

“所以我们这里有一些提示性的证据显示它们能解读这些图片，或许它们确实懂得一张生气的脸是它们不喜欢的事物。”