What does the lecture mainly discuss?

A: Professor Johnson, since you are an expert on problems that students face when they follow a course of study through the medium of English-if English is not their mother tongue. Can you tell something about them?
B: Sure. The problems can be divided into three broad categories: psychological, cultural and linguistic. The first two categories mainly affect those who come to study in Britain.
A: What are the psychological problems?
B: Some of the common psychological problems really involve fear of the unknown: for example, whether one’s academic studies will be too difficult.
A: What do you mean by cultural problems?
B: Well, looking at the cultural problems, we can see that some of them are of a very practical nature, for example, arranging satisfactory accommodation. Others are less easy to define. The largest category seems to be linguistic.
A: Can you be more detailed?
B: Yes. Most students, in their own countries, will have little opportunity to practice using English. When foreign learners first have the opportunity to speak to an English-speaking person they may have a shock: they often have great difficulty in understanding! I’ll just mention three of the possible reasons for this.
A: Oh, what are they?
B: First, it seems to students that English people speak very quickly. Second, they speak with a variety of accents. Third, different styles of speech are used. For all of these reasons students will have difficulty, mainly because they lack everyday practice in listening to English people speaking English.
A: What can a student do then to overcome these difficulties?
B: Obviously, attend English classes, and if a language laboratory is available, use it as much as possible. He should also listen to programs in English on the radio and TV. Perhaps most important of all, he should take every opportunity to meet and speak with native English-speaking people.
A: Then how can students overcome difficulties of speaking English?
B: Well, I think firstly, he must simplify what he wants to say so that he can express himself reasonably clearly. Secondly, he must try to think in English not translate from his mother tongue. This will begin to take place only when his use of English becomes automatic. Using a language laboratory and listening to English as much as possible will help.
A: Professor Johnson, you have quite enlightened us. Thank you very much.
B: You are welcome.