If you have severe problems with speaking, is it okay to use more text and equations on slides?
Slides with a lot of text or equations aiming to be self-explanatory tend to:
visually overwhelm the audience and don’t provide visual guidance – which is more relevant in talks than in written text as the audience needs to multitask to some extent, listening to the speaker and reading the slides at the same time;
contain more information than the audience can digest in the given time – regardless of what the speaker does;
have overly small text and graphics;
be read verbatim (which usually is a bad idea).
Mind the tend to: Neither are these issues inevitable, nor are they tied to the slides being self-explanatory. Rather, they are what often happens if an inexperienced speaker tries to make slides self-explanatory. In fact, I would consider most of my own slides self-explanatory and I am rather confident that my talks do not suffer from the above problems.
Hence I think your strategy to make your slides self-explanatory is fine – if you avoid the above problems. In detail, I recommend:
Avoid complete sentences, as they are bad for discontinuous reading such as usually done in talks.
Make sure that the main structure of each slide is easy to grasp.
Find a reasonable trade-off between not putting too much information on one slide and showing slides long enough. If possible, use some test audience to ensure that your slides can be comprehended within the allotted time.
If a slide is complicated, build it up step by step in pieces that can be assessed by the audience within seconds. Be careful not to overuse this feature, e.g., by uncovering a list item by item. The audience likes to read ahead, in particular if you are rhetorically challenged.
Self-explanatory does not mean containing all the details. In most cases, you barely have sufficient time to communicate your main message – only show what is essential to this message or at least make sure that sidenotes are visually distinct. For example, if there is a standard way to choose the temperature at which you conduct your experiment, you usually don’t need to write this on your slide. If you know that there are some people who cannot stop themselves from asking about this or it may be interesting for some members of the audience, give this information on the slides in a smaller font size or visually separate (and don’t talk about it).
One additional idea to consider—you may want to treat what you're going to say as a "script" and memorize it. There's a lot of research that shows that reciting a speech (or similarly, acting or singing on stage!) uses different parts of the brain than normal everyday speech. You may find that it bypasses your nervousness and allows you to get through the talk.)
If you have severe problems with speaking, is it okay to use more text and equations on slides?
Sort of: to be more precise, it's only "okay" to the extent that it may be the least bad option available to you or in general to a speaker who has the sort of difficulties you alluded to. But sadly I think that there is no such thing as "self-explanatory slides" -- the closest thing is called a "paper", and is something people can consume without going to a talk. The whole point of a talk is to use the medium of speech to communicate ideas in a completely different, and potentially much more efficient, way than through static, written material. To hear other people present their ideas through speech is the reason people go to talks.
Note that I am not trying to belittle your difficulties. I understand that just telling you you have to speak when maybe you can't is not helpful, so that's not what I'm doing. I'm just saying I think a talk with almost no speech is seriously unlikely to end up being a good talk no matter how hard you try, since you will be trying to use the wrong medium for the format to convey your ideas. It is like trying to play tennis with a ping pong paddle -- it can be done perhaps, but not well.
What is your advice on this in case of unusual limitations or problems of the presenter? Problems such as:
- nervousness up to the extent that language gets incoherent,
- people who do not speak the language required for the presentation well,
- people with voice problems.
My advice is:
If the problem is completely, hopelessly unresolvable, e.g., due to being related to a medical condition, then just do your best with the text and equations and any other tricks you can think of. Also consider giving fewer public talks and trying to build your reputation more through interaction with small groups of collaborators and students, and written communication media such as papers, emails, blogging etc.
If there is any chance that your speech difficulties could be resolved someday, even if it might be extremely difficult and require years of therapy, voice practice, intensive language tutoring, or even surgery or other medical treatments, I think you might want to consider making the effort. Presenting your work in public is an integral part of academic life (and certainly one cannot hope to get a job that involves teaching, which are 99% of academic jobs, if one cannot demonstrate having that ability at least at a reasonable level), so your prognosis for a successful academic career with very limited public speaking skills would not be a great one, unless you are a genius of Stephen Hawking's caliber. Sorry I can't sound more optimistic, and good luck.