『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 61 Lec1听力练习：Why does the professor discuss the length of some telephone numbers?原文题目答案解析，TPO/Official 61 Lec1听力原文范文音频翻译。

托福TPO/Official 61 Lec1听力原文Why does the professor discuss the length of some telephone numbers?【新东方在线】

Narrator: Listen to part of a lecture in a sociology class.

教授： 社会学实际上是一个跨学科的领域。

Professor: Sociology is really a cross disciplinary field.

我们在研究特定现象时，经常会发现生物学、心理学以及其他科学领域的元素相互重叠。

We find that elements of biology, psychology, and other sciences often overlap as we study particular phenomena.

让我介绍一个来自认知心理学的概念。

So let me introduce a concept from cognitive psychology.

假设有人让你看一张清单，并尽可能多地记住上面的项目。

Okay. Let's say someone asks you to look at a list and memorize as many items on it as he can.

大多数人平均能记住七个项目。这个记忆测试有几种变化形式。

Most of us are able to remember, on average, seven items. There are several variations of this memory test.

而结果始终显示，人类短期记忆的极限是七个信息单位。

And the results consistently show that the human limit for short term memory is seven bits of information.

信道容量是指在特定连接（比如我们的大脑）上传输或接收信息的数量。

Channel capacity is the amount of information that can be transmitted or received over a specific connection, like our brain

对于短期记忆来说，它的信道容量有一些有趣的实际生活应用，比如电话号码。

and the channel capacity for our short term memory, it has some interesting real life implications, like phone numbers.

在美国，本地电话号码都有七位数字，因为电话公司很早就意识到更长的号码会导致更多的拨号错误。

Local numbers here in the United States all have seven digits, because the phone companies realized early on that longer numbers would lead to a lot more wrong numbers being dialed.

但信道容量的概念不仅仅适用于我们的认知能力，它也影响着我们与周围人的关系。

But the idea of channel capacity doesn't apply just to our cognitive abilities. It also affects our relationships with people around us.

Psychologists talk about sympathy groups.

这些是我们最关心的人——亲密的朋友和家人，我们投入最多的时间。

These are the people, close friends, family to whom we devote the most time.

我们经常打电话或见面，思考他们，担心他们。研究表明，每个人这样的群体大约有10到15个人。

We call or see them frequently. We think about them, worry about them. And studies show for each of us, the size of that group is about 10 to 15 people.

当然，关系需要时间和情感投入，而大多数人都没有无限的时间和情感资源。

Sure, relationships take time and emotional energy, and most of us don't have unlimited amounts of either.

但如果还有另一个原因呢？如果是我们大脑设定了这个限制？

But what if there's another reason? What if it's our brain, that setting the limit?

实际上，有证据表明，我们的社交信道容量可能实际上是大脑大小的函数，或者更准确地说，是我们大脑皮层的大小。

And in fact, there's evidence that indicates that our social channel capacity may actually be a function of our brain size, or more accurately, the size of our neocortex.

大脑皮层是哺乳动物大脑的前部区域，与复杂思维有关。

The neocortex is the frontal region in the brain of mammals that's associated with complex thought.

灵长类动物在哺乳动物中拥有最大的大脑皮层。

Primates have the largest neocortexes among mammals.

但在不同的灵长类物种中，人类、猿类、狒狒，大脑皮层的大小有所不同。

But among different primate species, humans, apes, baboons, neocortex size varies.

关于这些差异有很多理论被提出，比如是否与使用工具有关。

A lot of theories have been proposed for these variations. Like maybe it's related to the use of tools.

但在20世纪90年代末，一位名叫罗宾·邓巴的人类学家发表了一篇关于灵长类动物研究的文章，之前的理论似乎都不够完美，直到他的研究出现。

But no theories ever seemed like a perfect explanation until the late 1990s, when an anthropologist named Robin Dunbar published an article about his studies of primates.

邓巴的理论是，如果你观察任何一种灵长类动物，你会发现，如果它的大脑皮层更大，那么它生活的社会群体就更大。

Dunbar’s theory is that if you look at any particular species of primate, you'll find that if it has a larger neocortex, then it lives in a larger social group.

以人类为例。我们有最大的大脑皮层，我们也有最多的社交关系。

Take human beings. We have the largest neocortexes. We have the largest number of social relationships.

我们已经说过，我们的同情群体大约有10到15人。

So we've said that our sympathy group is 10 to 15 people.

但是除了家庭和亲密朋友之外的其他关系呢？例如那些发生在工作场所的关系？

What about our other relationships other than family and close friends, such as those that occur in the workplace?

我们称这些为社交群体，而不是同情群体。

We’ll call these social groups as opposed to sympathy groups.

How many relationships can we handle there?

这些关系不像前者那样深入，所以我们可以处理更多。但是否存在上限？

Those relationships aren't as involved, so we can handle more of them. But is there an upper limit?

邓巴认为存在一个上限，并开发了一个方程来计算它。

Well, Dunbar says that there is, and he developed an equation to calculate it.

他的方程依赖于知道大脑皮层大小与整个大脑大小的比例。

His equation depends on knowing the ratio between the size of the neocortex and the size of the whole brain.

即在整个大脑中，大脑皮层占了多少比例？

That is, of the whole brain, what percentage of it is taken up by the neocortex?

一旦你知道了任何特定物种的平均百分比，这个方程就能预测该物种的最大社会群体规模。

Once you know the average percentage for any particular species, the equation predicts the expected maximum social group size for that species.

对于人类来说，这个数字似乎约为150。

For humans, that number seems to be about 150.

因此根据邓巴的方程，我们的社交群体人数很可能不会超过150人。

So according to Dunbar’s equation, our social groups probably won't number more than 150 people.

邓巴的假设并不是那种容易通过空着变量实验来证实的东西，但有一些轶事证据支持它。

Now, Dunbar’s hypothesis isn't the kind of thing that's easy to confirm in a controlled experiment, but there is anecdotal evidence to support it.

作为他研究的一部分，邓巴研究了21个不同传统狩猎采集社会的历史记录。

As part of his research, Dunbar reviewed historical records for 21 different traditional hunter-gatherer societies.

这些记录显示，每个村庄的平均人数刚好低于150，确切地说是148.4人。

And those records showed that the average number of people in each village was just under 150, 148.4 to be exact.

邓巴还与生物学家合作，看看他的假设是否适用于除灵长类以外的其他哺乳动物。

Dunbar’s also worked with biologists to see if his hypothesis applies to other mammals besides primates.

当他们研究食肉哺乳动物时，发现大脑皮层更大的动物也有更大的社交群体。

When they looked at meat eating mammals, carnivores, they found that the ones with a larger neocortex also have a bigger social group.

这些群体中的个体数量是由邓巴的方程预测的，从而支持了他的假设。

And the number of individuals in that group is predicted by Dunbar’s equation supporting his hypothesis.

但是当他们研究食虫动物（即吃昆虫的哺乳动物）时，结果并不一致。

But when they looked at insectivores, mammals that eat insects, the results were inconsistent.

数据并没有反驳邓巴的假设，但它不像对食肉动物的研究那样完美匹配，这并不完全令人惊讶。

The data didn't disprove Dunbar’s hypothesis, but it wasn't a nice, neat match like the carnivore studies, which isn't totally surprising.

食虫动物很难观察，因为它们中的许多只在夜间活动，或者大部分时间都在地下度过。

Insectivores are hard to observe, since many of them only come out at night or they spend a lot of time underground.

所以我们对它们的社会关系了解得比较少。

So we know a lot less about their social relationships.

Why does the professor discuss the length of some telephone numbers?

What does the professor imply about the size of a person's sympathy group?

What did Dunbar's study of the records of some traditional hunter-gatherer societies indicate?

What does the professor say that biologists discovered in their research of animals other than primates?

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