托福听力内容主旨题如何抓取关键信息？

>>托福听力：托福听力内容主旨题如何抓取关键信息？

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内容主旨题(Gist-Content Questions)

托福考试涉及的语言能力考查都是在校园学术的环境下，因此听力考试中的lecture就是模拟大学课堂里教授介绍某个学科的知识概念的情景。通常来讲，教授主要有这么几种方式来引出主旨，这也是在真实的校园课堂情境中，教授会用到的方式。

开门见山

讲座开头教授就直接点明了主要内容，而正确的选项就是对讲座中教授所说内容的同义转述(paraphrase)。例如TPO41Lecture1 Desert plants。

听力原文：

Many organisms have developed the ability to survive in harsh environmental conditions: extreme heat or cold, or very dry conditions. Like plants in the desert. Your textbook doesn't have much about the specifics on desert plants, but I think that desert plants are great examples of specialized adaptations to extreme environmental conditions.So, with desert plants, there are basically three different adaptive strategies. And I should point out that these strategies are not specific to any particular species. Many different species have developed each of the adaptations.

题目：

What is the lecture mainly about?

A. The growth rates of plants in different geographical regions

B. Different ways that plants have adapted to desert environments

C. The different mechanisms that plant roots use to absorb water

D. Different kinds of succulent plants

答案：B

这篇讲座的开头教授通过一个强转折“but”来强调后面的内容更重要，然后直接就说了沙漠植物有三种适应的方式，接着整篇讲座分别介绍了这三种方式，正好对应主旨题中的B选项。而其他三个选项内容，都是讲座中提到的局部信息，也就是细节，因此不能概括全文的主要内容，应排除。

导入式介绍

当然，在大多数的情况下，教授对于主要内容的引入并不会这么直接(ETS也不会用这么简单的方式来考)，更多的情况是先对上节课的内容进行回顾，或者先介绍一下所讲主题的背景再展开主题。这就要求同学们需要注意听信号词提示，再根据听到的内容来对应正确选项。例如TPO14Lecture1 Cognition。

听力原文：

We’ve said that the term “cognition” refers to mental states like knowing and believing, and to mental processes we use to arrive at those states. So, for example, reasoning is a cognitive process, so is perception. We use information that we perceive through our senses to help us make decisions, to arrive at beliefs and so on. And then there are memory and imagination which relate to the knowledge of things that happen in the past or may happen in the future. So, perceiving, remembering, imagining are all internal mental processes that lead to knowing or believing. Yet, each of these processes has limitations and can lead us to hold mistaken beliefs or make false predictions.

题目：

What is the lecture mainly about?

A. The differences between imagination and perception.

B. Cognitive functions that improve decision making.

C. Cognitive functions that assist in problem solving.

D. Common limitations with regard to several cognitive functions.

答案：D

教授在讲座开头先解释了什么是“cognition”，还举了“reasoning，perception”的例子来说明这个概念，接着教授用了“Yet”来表示转折强调，说这些过程都有局限性(limitations)，然后分别举例讲了三种认知过程的局限性。因此，只有D选项提到了limitations，B，C两个选项用improve，assist，与原文的信息不符;原文分别讲了imagination和perception，却没有提到A选项所说的两者的differences。

结合全篇概括

还有一种情况就更不友好了，教授并没有明确说要讲的主题，而是直接开讲，同学们则需要通过听完全篇来概括，或者认真分析题目选项来排除错误选项，例如TPO45Lecture2 T-cells。

听力原文：

Professor: So that's the overview of the human immune system. But we have a few minutes left. Any questions? George?

Student: Yes,you talked about T-cells, naive T-cells. Can you go over that part again? And also why do we call them that anyway?

Professor: All right, they're...they're known as T-cells because they develop in the thymus.

Student: The what?

Professor: Thymus. That's T-H-Y-M-U-S. It's a small organ in the body. Anyway, that's why we call them that. They come from the thymus. And T-cells are a part of the body's immune system. They can recognize and eliminate cells from outside the body that might cause disease......

Professor: There is a lot of biochemistry involved that we'll get into in the next lecture. But your question reminds me about a study that some of my colleagues are doing. It relates to caloric restriction.

Student: Caloric? Like calories in the food we eat.

Professor: Exactly! We are talking about the sugars, carbohydrates, fats that our bodies burn to get energy which we measure in calories.Okay, let's back up a little.......

Student: Interesting. But what's the connection?

Professor: Oh, with the immune system? Well, it is been shown that the immune system becomes much less effective as animals age. That's true in humans too. We think those naive T-cells just get used up. I mean it is not like the body's always making lots of new ones. And over the course of a lifetime, as T-cells encounter more and more strange bacteria or whatever, the naive T-cells get turned into memory T-cells. So later on in life, there are fewer and fewer of these naive T-cells left to deal with any new disease- causing organisms that might attack, which means less immunity, and the animal or person is more likely to get sick.......

这篇讲座的开头就像是真实课堂中最后五分钟的Q&A环节，教授根据学生的提问解释了T-cells以及naive T- cells，接着教授说这个问题让我想起了关于calorie restricted的实验，一个是mice，一个是Rhesus monkeys，因为学生的提问，教授又解释了实验和T-cells的关系。通篇来看，讲座中并没有明确表示主要内容的句子，可是全篇占比重较大的是两个关于calorie的实验，那么我们来看题目的话就需要认真分析选项了：

题目：

What is the lecture mainly about?

A. The process by which immune cells are produced

B. The effects of consuming far fewer calories than usual

C. The function of an organ found in rhesus monkeys and in humans

D. The discovery of a nutrient necessary for good health

答案：B

A选项是说免疫细胞产生的过程，讲座中未提及是如何产生的，只说了T细胞的作用，因此不能选;B选项是在讲比正常消耗更少的卡路里会产生的效果，因此对应到了两个实验，即消耗更少卡路里的老鼠和猴子的平均寿命要长一些，为正确选项;C选项只是讲座中提到的一个细节，猴子的实验，是局部信息，不能选;D选项的discovery是无关内容，因此排除。

综上所述，不管哪种主旨展开方式，回答内容主旨题的原则是要排除过细的选项，需要选择立足于整篇的概括性的选项。

通过上面的描述，我们知道了内容主旨题该如何抓取关键有效的信息。所以考生在复习这类题型时，要针对性的复习，多运用一些考试技巧，才能有效提高自己的托福考试成绩。如果你们还想了解有关如何提升自己考试成绩的技巧方法，就请继续关注坦途网托福考试频道吧。