Is it a bad idea not to use slides in my Ph.D. oral defense?

Question

I am preparing for my Ph.D. oral defense in mathematics and am reading tips from various resources. It seems that the usage of slides is usually assumed, though it is generally not required. For me, I am more used to the more traditional way; that is, using whiteboard and markers. I have almost never used slides in my past part-time teachings.

My questions:

1. Is it a bad idea to use whiteboard and markers instead of slides in my Ph.D. oral defense?
2. If I use whiteboard, what if the committee have questions about the contents that I have already erased in my presentation?

Answer 1

I have seen plenty of thesis defenses that use blackboards (the boards in our department are black- rather than white-, but I don't see that it makes a difference) and also plenty that have used slides. You should ask around -- or remember from previous thesis defenses you have attended; these are almost always open to all interested parties -- to see whether there is any local preference between slides and writing on the board. Ask your advisor too.

I suspect that you will find that it is up to you. In that case: do what makes you feel comfortable.

Is it a bad idea to use whiteboard and markers instead of slides in my Ph.D. oral defense?

No, if you know it will make you more comfortable and more able to present well, it's a good idea.

If I use whiteboard, what if the committee have questions about the contents that I have already erased in my presentation?

I don't see any fundamental difference between a thesis defense and any other math presentation. In general people can ask questions at any time; if the speaker indicates that she would rather address them later, then they get addressed later, in which case it's up to both the speaker and the questioner to remember the question (e.g. someone could write it down). A question which is specifically pertinent to something complicated you wrote on the board is probably better addressed then rather than later. If you get a later question about something that's not on the board anymore, your options are to answer the question verbally, to rewrite something on the board, or to pass out some other written materials which address it.

I will mention in passing that mathematical culture seems to prefer "chalk talks" more than general academic culture at this point. I have absolutely never used slides / powerpoint / whatever in any class I've taught. I do it only at large conferences where I can't be confident in advance that the board will be available and easily visible to all and/or that I've been given such a short amount of time that I feel that I have to whip through slides at top speed in order to "cover" what I want to. Writing mathematics on the board takes time. But so does understanding mathematics, and it feels a bit dishonest to need to present material faster than you can write it on the board. Moreover, if you're writing then you can adapt your presentation to the audience on the fly (which for a thesis can be important, so that e.g. having a thesis defense in a room with nothing to write on at all would seem weird to me).

Good luck.

Further Thoughts: Many thesis defenses have two very distinct parts, and the first part really is a lot like a conference talk in that you have a set amount of material to "cover" and the general expectation that you will get through that "coverage" with little distraction. So doing slides for that part of the defense makes perfectly good sense to me: a thesis defense is not a lecture, and the goal of that part of the defense is not to impart the maximal possible understanding to everyone in the room. You want to get through that first part with little fuss, and you don't want it to drag out. So for instance if you are the type of person that prepares much more to write on the board than turns out to be realistic (as I often am), then preparing slides could be a good strategy to stay on track. Still, if you want to write on the board during this part of the defense: go for it.

Answer 2

There is another option, that gives the best of both worlds: use transparencies on an overhead projector! Your department will probably have one buried in the dungeons somewhere.

Some projectors have a continuous roll of film that you scroll up and down over the surface you write on, with others you'll need to use individual A4 transparency sheets. If you use a clear numbering system, it's easy for the audience to ask you to go back to a specific spot.

You can even draw complicated diagrams by hand in advance, or print some sections onto transparency paper. But you still have that possibility to write directly onto what you're projecting that you can only do with a computer presentation if you have a "smart" whiteboard or a digitizer tablet.

Answer 3

Let me answer question 2 first, since it is easier.

• You can highly encourage your examiners/audience members to interrupt you at anytime with questions. (This prevents the problem from happening.)
• Additionally prepare some written notes and when giving your presentation use clear and consistent numberings/namings of equations and theorems. (This makes it easier for the audience to scribble down the context of their question, and for you to recall the statements later.)

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Question 1 on the other hand depends on a lot of factors.

1. Is your oral defense "serious" or "pro forma"? In the first case it is often better to use whichever you are more comfortable with (but read on for the points below). In the second case you should just use slides (it saves every one some time and gets you out of the room to enjoy the champagne that much quicker). Since in the second case you don't really care about giving a good talk, we will assume you are in the first case for the following points.

2. Slides doesn't mean faster. While it is possible to abuse slides and give talks at a higher pace than you would otherwise (and hence should), it is considered bad practice by many to use slides for the sake of "covering material". Your job in giving an academic presentation is not to simply show off how much stuff you know, but to convey a sense of narrative to the project and to impress on the audience the actual knowledge you have discovered.

   • If you are covering the slide from top to bottom with words, you are doing it wrong.
   • If you have more slides than minutes for the presentation, you are probably doing it wrong.
   • If you presentation can be presented without you (namely that the audience can just read the slide from beginning to end without you being involved), you are doing it wrong.

   The keyword in visual aid is "aid". Most people find it difficult to process two different streams of verbal information at the same time. If you use slides you should use keywords and phrases to anchor the attention of the audience, but not full sentences (which would be an invitation to stop listening to what you are saying).

3. Board doesn't mean slower. You don't have to write down every word that comes out of your mouth. Mathematics excels in having symbolic notation. And while it is good to state your theorems in a reasonably complete way, for technical hypotheses you don't necessarily have to write it down (unless that hypothesis is sort of the point of the presentation): you can simply give names to your hypotheses and express and explain each of them orally.
4. Is your penmanship good? This is obviously a concern for the decision between board versus slide. If your board writing is perfectly illegible, you really should use slides. Even if all your peers use the board.

5. Some further comparisons (in no particular order)

   • Slides force you to adopt a fixed linear narrative, and it is harder to jump out of it on the fly. Board allows you to be more free-form. On the flip side, if you are very nervous about your presentation, the regimental nature of slides may help you settle into a groove more easily.
   • Slides do allow you to race through material. If you are the type that when excited will start talking faster and faster, maybe the action of writing on the board can help prevent you from blitzing through your talk at an incomprehensible speed.
   • If your talk has a time-limit, one benefit from a board-talk is that you can adjust your presentation on the fly to accommodate the limit. It doesn't look good if you give a slide talk and either finish 10 minutes early or end up with 15 slides that you never got to. (You can do adjustments for slide talks too, but it is harder to hide it from the audience.)
   • If your talk uses a lot of pictures, I would recommend slides. Very few people are talented enough to draw great illustrations on the fly on the board. The same applies to any material that will take significantly longer to reproduce on the board than the time it will stay up on the board.
   • On the other hand, if your illustrations are "dynamic", it can sometimes be done better on the board. (Example: reproducing a straight-edge and compass construction, or illustrating Reidemeister moves in knot theory.)

6. In mathematics at least, both are common enough that you really shouldn't feel the need to conform to using one or the other. Ultimately your decision should be determined by "how can I give the best presentation?" while factoring various things like nerves (you will be nervous at your oral defense, regardless of how many talks you have given before; the same is true of your first tenure-track job talk, your first talk at a large conference, etc.) Of course you should spend time to prepare the content of your talk. But you should also spend time to discover the common pitfalls of public presentation (I listed some above, but the list is by no means complete) and make the effort to take preventative actions. One way to do the latter, as has been suggested elsewhere on this page, is to go to other students' presentations. Wisdom is in large part learning from other people's mistakes.

Answer 4

The answer to your first question is hidden in your second question. Usually the questions are asked after the presentation and hence you might be asked to go to previous slide when the opponent might have a question or doubt. Also if people will ask you questions in between the presentation which is considered as rude behaviour on their part, might destroy your concentration and flow during presentation. Being a defence related to mathematics you might need a chalk and board anyhow as you can say everything on the ppt presentation, so you might need it to explain something not present in your slides.

Overall my recommendation is to use ppt slides for the main presentation and also keeping chalk and board handy for odd questions not covered in the slides.

Good luck with your defence!!!

Answer 5

I recommend the blackboard. Shows your process of thought better. Plus more old school. Unless you have complex graphics, skip the slide show.

Answer 6

Well to give a better understanding visualization is needed. During defense you main aim is to make people understand what you were doing and how good it is. If you feel you can make them understand without the slides go for it.

Answer 7

You should not compare presentations (at a defense, at a conference, etc) and teaching. A presentation does not necessarily explain the material, and its main purpose it to advertise your work in the presence of time constraints and stress. All blackboard presentations that I saw, put the presenters at a disadvantage. They would waste time copying from their notes to the board, fixing mistakes, then searching what's the next thing to copy. If you need to make a presentation, don't do it on blackboard.