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.

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.

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.”

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

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.

George Gershwin, born in 1998, was one of America's greatest composers. He published his first song when he was eighteen years old. During the next twenty years he wrote more than five hundred songs.

Many of Gershwin's songs were first written for musical plays performed in theatres in New York City. These plays were a popular form of entertainment in the 1920s and 1930s. Many of his songs have remained popular as ever. Over the years they have been sung and played in every possible way — from jazz to country.

    In the 1920s there was a debate in the United States about jazz music. Could jazz, some people asked, be considered serious music? In 1924 jazz musician and orchestra leader Paul Whiteman decided to organize a special concert to show that jazz was serious music. Gershwin agreed to compose something for the concert before he realized he had just a few weeks to do it. And in that short time, he composed a piece for piano and orchestra which he called Rhapsody in Blue. Gershwin himself played the piano at the concert. The audience were thrilled when they heard his music. It made him world-famous and showed that jazz music could be both serious and popular.

    In 1928, Gershwin went to Paris. He applied to study composition (作曲)with the well-known musician Nadia Boulanger, but she rejected him. She was afraid that classical study would ruin his jazz-influenced style. While there, Gershwin wrote An American in Paris. When it was first performed, critics (评论家)were divided over the music. Some called it happy and full of life, to others it was silly and boring. But it quickly became popular in Europe and the United States. It still remains one of his most famous works.

    George Gershwin died in 1937, just days after doctors learned he had brain cancer. He was only thirty-nine years old. Newspapers all over the world reported his death on their front pages. People mourned the loss of the man and all the music he might have still written.

A machine can now not only beat you at chess, it can also outperform you in debate. Last week, in a public debate in San Francisco, a software program called Project Debater beat its human opponents, including Noa Ovadia, Israel's former national debating champion.

Brilliant though it is, Project Debater has some weaknesses. It takes sentences from its library of documents and prebuilt arguments and strings them together. This can lead to the kinds of errors no human would make. Such wrinkles will no doubt be ironed out, yet they also point to a fundamental problem. As Kristian Hammond, professor of electrical engineering and computer science at Northwestern University, put it: "There's never a stage at which the system knows what it's talking about."

What Hammond is referring to is the question of meaning, and meaning is central to what distinguishes the least intelligent of humans from the most intelligent of machines. A computer works with symbols. Its program specifies a set of rules to transform one string of symbols into another. But it does not specify what those symbols mean. Indeed, to a computer, meaning is irrelevant. Humans, in thinking, talking, reading and writing, also work with symbols. But for humans, meaning is everything. When we communicate, we communicate meaning. What matters is not just the outside of a string of symbols, but the inside too, not just how they are arranged but what they mean.

Meaning emerges through a process of social interaction, not of computation, interaction that shapes the content of the symbols in our heads. The rules that assign meaning lie not just inside our heads, but also outside, in society, in social memory, social conventions and social relations. It is this that distinguishes humans from machines. And that's why, however astonishing Project Debater may seem, the tradition that began with Socrates and Confucius will not end with artificial intelligence.