What is the first thing you want to do when you see someone yawn(打哈欠)? You want to yawn, too! Yawning is contagious.

    Scientists have found that all people yawn. Babies start to yawn even before they are born. The earliest yawn takes place when a baby is still inside its mother. When young children are about one year old, they start to yawn when they see others yawning. That's why scientists seem to think yawning is contagious.

    It's no secret that yawning is contagious, but why do we yawn? Well, scientists are not really sure.

    Some think we yawn because we feel bored. Recently scientists studied two groups of students between the ages of 17 and 19. One group watched music videos, and the other watched a boring color test. Scientists compared the numbers of their yawns and found that the color test group yawned more times than the video group.

    Another reason about yawning has to do with breathing. Some scientists believe that when we are bored or tired, we breathe more slowly. As our breathing slows down, we cannot get rid of(去除) enough carbon dioxide (CO₂) in our bodies. When there is too much carbon dioxide, our bodies will tell the brains (大脑) to breathe deeply. The result is a big yawn.                                                           

    In 2007, scientists suggested a new reason. They said that the reason people yawned was to cool down their brains. These scientists found that people who were warmer than others yawned more often.

    Scientists are still trying to find out why yawning happens and why it is so contagious. But they are only sure that when one person yawns, almost everyone else nearby wants to yawn, too.

    Read the questions and answer YES or NO, then you will find out how good you are.

⒈When you don't understand something, you ask questions.

⒉You like listening to older people talk about the past.

⒊You think that you can learn something interesting from everyone around you.

⒋You are brave enough when you have to talk to people you don't know.

⒌You enjoy reading books about famous people.

⒍You always see and talk to different people.

⒎You are interested in learning new ways of doing things.

⒏You enjoy sharing experiences with friends and learning from people of all ages.

⒐You talk a lot about yourself.

⒑Even if you are often wrong, you make your own decisions.

⒒You hate teaching what you are good at: sports, technology and so on.

⒓Your parents don't understand you, so you don't talk to them much.

Score Now! (开始计分 )

    Score2 points if you answer YES to each of the first 8 questions, and 0 if you choose NO.

    Score 2 points if you answer NO to each of the last 4 question, and 0 if you choose YES.

    18-24. You are friendly and open-mind. You make people feel important by listening to what they have to say. You'll probably succeed in learning all kinds of interesting things.

    10-16. Remember that every single person you know can teach you something. You will great make your life rich and colorful.

    0-8 About 400 years ago, a famous writer wrote, “No man is an island.” This is still true today. Try to be more open and interested in people around you.

    Only humans speak using words. But all kinds in the animal world can communicate in one way or another. Maybe you have heard about the way bees dance around to send messages to each other and the way dogs bark in different ways to give warnings, to be friendly or to be playful. But did you know about infrasonic communication used by elephants? This is how it works:

    Humans hear low sounds like thunder rumbling in the sky. But we don't hear sounds lower than this. However, animals such as elephants and hippos can hear much lower sounds than humans can. And what's more, they can make those low sounds as well, and they use them to communicate with each other. This is known as infrasound.

    The amazing thing about infrasound is that it travels over several kilometers. Higher-level sounds like the one people can hear, don't travel well through walls, leaves, trees and so on, which is why we can't hear sounds from more than 100 meters away. But infrasound is much stronger and things like grass and trees have no influence on it. Therefore, it can travel much further. Elephants can hear infrasonic calls from four kilometers away!

    There have been reports of people watching groups of elephants feeding or resting and then the elephants suddenly all stopped what they were doing for no reason at all. They obviously heard a warning call from a long way away, but the people didn't hear a sound. In places like a zoo or wildlife park where you can get nearer to animals, it is a bit easier to sense when infrasonic sounds are made. When you stand near mother elephants with their babies in a zoo, you may notice a slight rumbling in the air every few minutes—not loud or strong, but clearly noticed. This is infrasonic communication—the mother elephants “talking” to their babies.

    Can plants eat people? Probably not, but there are many plants that eat meat. Some of them are big. And they can eat small animals. One famous meat-eating plant is the Venus flytrap(蝇草).

    The Venus flytrap is a very strange plant. It grows in dry parts of the United States. Its leaves are like the pages of a book. They can open and close very quickly. Inside the leaves, there are three small hairs. If a fly (苍蝇) touches one of the hairs, the leaf closes quickly. The fly cannot get out. In about half an hour, the leaf presses the fly until it is dead. Then, the plant covers the fly. Slowly, the plant eats the fly.

    Why do plants do it? Most plants get what they need from the sun, the air, and the ground. In some places, the ground is very poor. It doesn't have all these important things, especially nitrogen(氮).Animal meat has a lot of nitrogen, so some plants eat meat to get what they need. Let's hope that some of the bigger plants don't get the same idea!