在托福听力的很多讲座中，教授常常会在开头部分介绍一个现象或提出一个问题。然后接下来在主体部分就相应地给到解释这个现象的理论或假说，或者围绕这个问题提供相应的解决方案或证据支持等等。这都可以归类为南京环球教育（原环球教育）张雪蓓老师在课堂上详细介绍过的Phenomenon-Theory Model或它的延伸模型Problem-Attempt Model。

　　那么，什么是Phenomenon-Theory Model？跟随环球教育老师来简单回顾下，如图1所示，在所节选的讲座中，这个模型分两部分：1.介绍某个现象；2.提供可能解释。

　　具体地说，首先教授会介绍这个学科中的一个具体现象（它的本质是结果/effect），例：恐龙灭绝(The dinosaurs were gone) （针对一些术语或概念，教授可能还提供一些定义。）然后主体部分教授会给出一些可能的理论／假说／解释(theory/hypothesis/explanation/possibility)说明这个现象，这里就是“为什么恐龙会灭绝”。

　　在这个理论中，教授肯定会提到是什么可能的原因导致之前介绍的现象（结果）的；同时，另外我们还需要注意的是教授如何examine对这个理论，中文就是“对理论／解释的反思评价”，包括是否有证据／Evidence支持或反对、或理论本身有没有什么潜在的问题／局限等。

　　图1

　　在经典的Phenomenon-Theory Model之下，我们还可以根据具体的内容做延伸。我们知道这个模型的核心就是“批判性思维/Critical Thinking”。核心不变，内容稍作调整，可以延伸为Problem-Attempt Model，如图2。

　　图2

　　本文的主要目标是，不仅回顾Phenomenon-Theory Model及其延伸Problem-Attempt Model；同时还以TPO 31 L4 Domesticated Animals为例给出具体阐述。

　　讲座主题是Botai People驯养horses，希望找出可以说明horses domestication的证据支持。

　　整体上，运用Problem-Attempt Model，我们将内容提炼如下表：

　　［听力文本］

　　Professor: So now that we've discussed how people in ancient societies tamed animals like cows and chickens for food and other uses. I'd like to talk about an ancient culture that domesticated horses. It's the Botai people. The Botai culture thrived over 5000 years ago in central Asia, in what is now northern Kazakhstan. Pretty much all of what we know about the Botai comes from three archaeological sites. And we learned that the Botai were able to build large perennial villages, sometimes with hundreds of homes. We also found horse bones at these sites and these can be traced back to the time of the Botai settlements. The climate that the Botai culture lived in (laughing), it was harsh. And the Botai people, they didn't really seem to have much in the way of agriculture going on. So their whole economy was really based on horses. And because horses can withstand the tough climate, they can survive ice storms and they don't need heated barns, the Botai people could settle in one place and rely on the horses for food, clothing and transportation.

　　Student: So the Botai were the first to domesticate horses?

　　Professor: Well, we are pretty sure that horses were first domesticated a bit earlier, to the northwest, in the area that is now Ukraine and western Russia. It's quite possible that some of those people later migrated east to Kazakhstan.

　　Student: But what exactly tells us that these Botai people, that the horses in their area were really domesticated?

　　Professor: As with most ancient history, there is not much that we can be certain about. But we know there was a significant population of wild horses in that area. So there were plenty of opportunities for the Botai people to find horses to domesticate. We also know that horse milk was an important source of food for the Botai people. What? Milking a wild horse? Well, now that would be impossible, to milk a wild horse. And then, there's the. Oh. Yes? Eric.

　　Student: So you said last week that for some animals, like for dogs, there were physical changes taking place over the course of generations of dogs because of domestication. So can we tell from those horse bones if it was sort of the same for horses?

　　Professor: Actually, it wasn't. We know that horses have not changed a lot physically as a result of domestication. So those ancient horse bones don't tell us much about domestication. But, we've found that, um, we've found what maybe pens or corrals in the Botai settlements. And not too long ago, a new approach was used to find out if the Botai people were keeping horses. Soil samples from these pens or corrals show ten times the concentration of phosphorus.

　　Student: Um, phosphorus?

　　Professor: Yes. Phosphorus is a very significant indicator that horses, a large numbers of horses were being kept in the settlements. You see, horse manure, horse waste is rich in phosphorus and also nitrogen compared to normal soil. But nitrogen is an unstable element. It can be washed out when it rains or it can be released to the atmosphere, whereas phosphorus combines with calcium and iron, and can be preserved in the soil for thousands of years.The soil from the Botai settlement sites was found to have high concentrations of phosphorus and low nitrogen concentrations, which is important since it suggests that what we've got is really old, not something added to the soil more recently.

　　Student: Wait. So if horses have been there recently, there'd still be lots of nitrogen in the soil.

　　Professor: That's right. Yes? Karen.

　　Student: I just read an article. It said that one way to determine if there was an ancient fireplace at an archaeological site was to check the soil for phosphorus. So couldn't the phosphorus at the Botai sites just be from the frequent use of fireplaces?

　　Professor: You are absolutely right. However, when a fireplace leaves behind a lot of phosphorus in the soil, we'd also find an unusually high concentration of potassium. But the soil at the Botai settlements, it was found with relatively little potassium, which makes it far more likely that that the phosphorus came from horses. OK? Now, later on, people of the same region, northern Kazakhstan, started raising sheep and cattle. And that led to a more nomadic culture. Since sheep and cattle can't survive harsh climates, they needed to be taken south every winter. Moving around meant working harder but the trade off was far richer, fattier milk year round and warm clothing from the sheep.