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随身英语Why we yawn 我们为什么打哈欠？ 请注意，点开这篇文章可能会让你打哈欠！这并不是因为我们的节目太无聊或者你会被传染上哈欠，而是因为只要我们看到别人打哈欠，甚至只是想想这个行为，都可能引发我们来一个大哈欠！但这究竟是为什么呢，本集《随身英语》将会解答你的疑惑。 课文内容 Vocabulary: Biology 词汇:生物学 It’s a question that has puzzled scientists for a long time: why exactly do we yawn? In a recent breakthrough, scientists have discovered the part of the brain responsible for contagious yawning. It’s called the primary motor cortex, and controls movement in the body. When triggered it makes us yawn. But we can’t choose to yawn – it’s an involuntary imitation of other people. You know how it goes: your friend yawns, you yawn. Knowing which section of the brain is involved is only part of the answer. There is still a deeper question of ‘why’. And we don’t only yawn when others do, we sometimes yawn alone. So, let’s start with the physiological theories behind yawning. As far back as 400BC, Greek physician Hippocrates speculated that yawning released harmful gases from the body, like “steam escaping from a cauldron”. His colourful theory is now, sadly, discounted. A more recent idea suggests that we yawn in order to cool down the brain. Just like a busy computer processor, our brains can overheat. Psychologist Gordon Gallup from the University at Albany has argued that the act of yawning delivers a rush of oxygen to the brain, helping us think more clearly. | 
