People have always wanted to speak with animals. There are many books about this, especially children books. Now there are also movies, such as Dr. Doolittle. When you watch animals, it seems clear that they can communicate with each other. Many people wonder why people can't also communicate with them.    Scientists know how some animals communicate. Bees, for example, use their bodies. They do a kind of dance to give information about food. Birds, on the other hand, share information with sounds. They use certain sounds to protect their homes and to stay together when they fly. Some male birds use lovely songs to attract a female . Other animals communicate with both body movements and sounds. For example, dogs wag their tails when they are happy, and they bark when they are excited.    People used to think it was possible to teach human language to animals. Parrots and other birds, for example, can learn to say words. But the birds just repeat the words. They don't understand them. Some American scientists tried to teach English to chimpanzees , close  s of human beings. However, this was impossible. Chimpanzees can't move their mouths the right way. They could never learn to speak like people.    Then scientists tried to teach human language to chimpanzees in other ways. Some tried with American Sign Language (ASL). Others tried with a simple computer. But chimpanzees could only learn to use a few words. They could never learn to use grammar. Their brains are very different from the brains of human beings.    Now some scientists are studying the same points between human and animal language. In fact, some animals use sounds like people do. Dogs, for example, use an unpleasant, low sound to tell other dogs to stay away. People, too, use that kind of voice to say the same things. A dog's noisy bark communicate that something is happening. People use the same high tone when they shout, "Watch out!"    Scientists want to understand the language of other animals, such as whales and bears. To do this, they go out to the animals' natural homes. They watch the animals for days or even years. They take pictures and make tape recordings and share the information with other scientists. In this way, they hope to learn more about the way animals communicate, and maybe someday we'll be able to communicate better with them. This passage is mainly about   _  .
how scientists communicate with each other how scientists are studying animals' communication how people might communicate with animals how animals communicate with each other