So, you've finally submitted your thesis. Big step, big relief, isn't it? And now you have ahead of you the last chapter of your PhD, your viva. It is understandable that it can be a bit intimidating. However, try to feel confident about it. You've been working on your thesis for so many years. There's no way your examiners have better knowledge than you in this specific topic. They of course have broader knowledge in the general field you are researching, but for sure they haven't seen what you have been doing. Otherwise, you wouldn't be doing a PhD.

Before the viva

Go through your thesis as many times as you can. Make sure you remember very well every single detail of your research. You'll be surprised how easy it is to forget, even though it's your own stuff! But it kind of makes sense, doesn't it? There might be some parts in your thesis, which you did two or three years ago. So make sure you refresh your memory! Make sure you know the methodology you followed in running your experiments and more importantly, the reason for doing it in this way. Also, try to anticipate the potential questions that could come up during your viva. Write them down and practise answering them. Also prepare a 5-10 minute presentation of your contributions. It is likely that you'll be asked you to make such a presentation. But even if you are not, it's still extremely helpful to have this kind of information in your mind and be able to use it during your viva.

During the viva

Obviously, listen carefully to what the examiners ask you and don't be afraid to ask them to repeat their question or clarify it. It's ok to pause for a moment if you need to take some time thinking. It's also ok to ask for a break if you feel you are getting tired and your mind needs to cool down for a bit. Try to explain as clearly as possible the reason you did something in your research in "this way", and not the "other way". It's always helpful if you can support your argument by examples from the literature. It's also possible that the examiners have not completely understood your research and as a result, they might view it as something trivial and not appreciate it that much. It's your job to convince them that this is wrong. Explain them why your research is novel, and how it complements the limitations that exist in the literature. Be passionate when you talk about your research. I trully believe that psychology can plan an important role in this kind of situations. If you seem confident and passionate when you talk, you can pass this condifence to the examiner, too. I'm not saying that you'll convince him for whatever you argument you make, but it could make your life easier.

It's out of my thesis scope

This is a phrase that you might need to use a few times during your viva. Because of the examiners' broad knowledge, they might start asking questions that are not exactly relevant to your research. Don't be afraid to say that what they are asking you is outside the scope of your thesis. Try to bring them back to the topic, it's important.

When a conversation around a topic lasts forever

I'm not sure how common this is, but it happened to me. We spent around one hour discussing more or less the same thing! In my case it was a question around my methodology and the examiners were having difficulties understanding some parts of it. You have to be patient and try to find different ways of explaining their question. If there is a board in the room, use it if you think it's going to help clarifying things. More importantly, don't panic. The fact that they are focusing on a single question doesn't necessarily mean that they have a problem with it. It could just mean that they are interested in it and they really want to understant how you've done it. But even if this is not the case, don't worry. It's their job to ask questions; remember that viva is also called a defense.

Not knowing an answer to a question

When you don't know or you are not sure of the answer to a specific question. Don't worry, it's ok and it happens (of course as long as it's not in something central in your work!). Try to remember from your previous academic years, when you were taking a written exam, you never needed to score 100%. Even if you got a few questions wrong, you could still pass. It's the same in the viva. You don't need to know everything. Admit that you are not sure about what they are asking you. But try not to leave it there. If possible, try to make a speculation, especially if you are dealing with a "what-if" question. I think it's more important to show the examiners that you are able of independant thinking. So if you can prove that, I believe it doesn't really matter if you don't manage to answer a couple of questions. Just show that you are a mature, independant and thinking scientist.