The Examiner's Aims in IELTS Speaking Part 3
The examiner's main aim in Part 3 is to give you opportunities to show the most advanced vocabulary, grammar and coherence skills that you know.
"Vocabulary" here includes "commonly used phrases and expressions". The vocabulary that you use in Part 3 should be a little more formal than in Part 1, where you speak about everyday things in your life and in Part 2, which is also connected with your life in some way. But your language should not be as formal as in the Writing test. In other words, you should try to speak vocabulary that is suitable for an educated person when speaking, not the vocabulary of quite formal written materials. (You need to recognize which words in "IELTS Vocabulary" books are more suitable for writing than speaking – some of the words in those books are not very suitable for spoken English.)
Coherence in Part 3
Showing coherence skills in Part 3 is especially important. One of the main reasons why Part 3 often has questions involving complex issues is to give you the opportunity to show your coherence skills. After you read what is written below, you'll see why it is so important to give answers in Part 3 that are longer than Part 1 answers. If your answers are short, you will be including fewer points in your answers and fewer points means fewer opportunities to show coherence skills. (As stated below, most of your Part 3 answers should be longer because they include "discussion-style" language such as the balancing of two or more contrasting points.)
The coherence skills that the examiner is looking at are basically the skills of speaking in a way that is easily understandable, i.e., easy to follow, when you are speaking in depth about several interrelated (complex) issues. At the same time, a rather long Part 3 answer should have a "wholeness" quality i.e., a quality of being unified. This "wholeness" quality is the feeling that everything you say is related to the original question, even when you give a lot of extra details and comments.
More specifically, the examiner is looking at your ability to express in words the logic of the interconnection between several ideas (several statements). Your language should be like this: Statement A + logical connection to Statement B + logical connection to Statement C + . . . . Usually, the logical connection words are at the beginning of the next statement, (followed by a comma in writing). The "statements" are usually separate sentences but you can make more than one separate statement made within one long sentence.
Some examples of words used to show logical connections are: "Therefore, …"; "So, …"; "As a result, …"; "On the other hand, …"; "Although X, … Y" (don't use "but" with "although"); "In contrast to that, …"; In other words, …"; "As well as that, …"; "For example, …"; "As I mentioned before, …"; etc.
These examples are commonly used "set phrases" or words and you should show the examiner that you have some knowledge of these. But you don't have to always or only use this kind of language to express logical connection, especially in speaking, which should be less formal than academic writing. For example, you might say Statement A (for example, the answer to the question, "What sorts of music do young people prefer to listen to?") and then you could follow that with the words, "But personally, …" + Statement B (where Statement B probably has words such as "I prefer to listen to …") Using the word, "But" is a less formal way to express the idea of, "In contrast to that, …" and a certain amount of less formal language is good in a speaking test. In fact, you don't have to use the word, "But" – you could just begin with, "Personally, …", which already includes the idea of "In contrast to that, …" but using the word, "But" emphasizes the contrast even more clearly.
The logical connection words do not always have to be the beginning part of the next statement – they can sometimes be a complete sentence themselves. In spoken language, it's quite natural to sometimes speak like this: "I can give you some examples (of that)." This is a complete sentence that serves the purpose of connecting two statements. Notice that by using the words, "of that", you are helping the listener to keep track of (to follow) your logic because you specifically refer back, i.e., connect to what you previously said. It's not 100% necessary to use the words, "of that" but it helps the listener to see your connection.
Taking You to Your Upper Limit
To some extent, the examiner will try to take you to your limits of English, to see where you "break" or cannot answer. The point where you cannot answer (even when you understand the question) gives the examiner information about the upper limit of your speaking ability.
For example, the examiner might be quite sure that you are at least a Band 6.0 but he or she might not be sure whether you are good enough to get 6.5 or even 7.0. So they will test you with a few difficult questions and if you can answer those questions well, they will try even more difficult questions, in order to find your upper level. In other words, there is a good chance that the last one or two questions in Part 3 will be questions that you can't answer at all or questions that you give very poor answers to. Don't think that you "failed the test" if this happens because this happens to many candidates, even those at the Band 7 or 8 level.
However, not every test is like that because sometimes the examiner is quite sure what your upper limit is after just a few questions in Part 3, so he or she has no need to take you to your "breaking point".
If you do get questions that seem to be testing you to your limit, you should not feel scared or lose confidence. Instead, you should feel lucky (!) that the examiner is giving you an opportunity to move up half a Band point or even one whole Band point, and you should try your best.
Included in this idea of "taking you to your limit", is the difficulty of the language used in the questions. Although examiners usually try to simplify the questions in Part 3 so that you you can understand them the first time the examiner asks those questions, sometimes the examiner does not worry too much about doing this. Sometimes examiners deliberately ask questions using rather complex grammar or vocabulary in order to gain information about your knowledge of grammar and vocabulary – if your answer demonstrates that you understood the question, then that gives the examiner some information about your English level, although that is your listening comprehension level, not your speaking level.
More than testing your listening comprehension, the examiner usually uses rather difficult language in a question as a way of encouraging you to (try to) speak at that level of language in your answer. If all the questions in Part 3 were asked in quite simple English, then it would be quite natural for you to feel it is unsuitable to answer using language that is at a higher level than the language of the questions. In other words, the examiner is trying to encourage you to use your highest level of language by asking questions in quite high-level language.
Another reason why an examiner sometimes doesn't worry about simplifying a question using difficult language is that the examiner is testing your ability to seek clarification about the question, if you need to. Your ability to seek clarification about a question is itself an important communication skill in a discussion situation, a skill that requires knowledge of some particular language.