Why is it useful to give good talks?

As scientists you will give talks. Presenting your work:

What You'll Learn

What You'll not Learn


Material contained here is based on:

This tutorial is mainly meant for scientists, but several tips can be useful for other types of talks.

About the author

I am a physicist at Cosmostat, CEA Paris-Saclay. That's me: https://www.valeriapettorino.com/

Set your goals

The first step into preparing your talk is identifying what are your objectives: are you applying for a job, looking for a new expert collaboration, giving an outreach talk to the public, are you teaching, do you want to learn something yourself?

My personal goals for this tutorial:

What you are saying is not important ‘per sé': it becomes important if someone listens. It's in your interest to help your audience! If you know your audience, and what their expectation is, you can better target your talk and manage attention.

Who are you talking to?

What is their expectation?

Depending on the situation, you may have to compromise between your goal and your audience expectation.

Value your audience effort

In most cases, people in the audience:

In the next section you will find examples of talks aiming at different goals and audiences. Before reading further, can you think of how would you adapt your talk to the following use cases? How are they similar and how the following talks will differ? What should you focus on? What would you rather not do?

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Below you find a possible description of each of the following use cases:

1h Lecture

✅ Define everything and start from basic concepts

✅ Simplify communication as much as possible

✅ Adapt to feedback

✅ Consider interactive tools, live exercises, video.

✅ You may include some historical note on past attempts/developments

❌ You won't typically focus on your specific research

Time: Density of topics will be flexible, not really important to cover all topics within the 1h lecture.


20 m presentation to a committee panel

The committee will be asked to compare the story of each candidate. The talk is your chance to give your version of your story*

✅ why you are a good fit

✅ what is your specific contribution to science to far

✅ your responsibilities

Convince them that you can:

✅ explain clearly what you know

✅ value what they know

✅ be useful by providing something they don't know

❌ You are not teaching

⏰ Very efficient, it has to fit 20m:


40 m scientific seminar to experts in your domain

✅ Pick a specific new paper you wrote or result you obtained

✅ Give the context / motivation for your paper to exist

✅ Illustrate your new idea / implementation / result

✅ Clearly add the arxiv number of your paper to the slides

✅ Mention potential developments, targeted at the audience expertise

⏰ Take the time to explain the idea, main results, describe a scientific plot in detail.


1h colloquium

✅Give the context, with a very general introduction that everyone can understand (~15 m)

✅Describe main challenges in the field, not necessarily related to your work only (~10 m)

✅Describe how your work fits into addressing these challenges (~10 m)

✅Describe one result you got (~ 10 m) (for the experts in your field, otherwise they will be bored)

✅Describe potential developments in this field (~10 m) (for everyone)

✅Conclusions with your short and long term vision of this field (~5 m)

❌Not focused on a specific paper you wrote.


Public outreach talk (ex. TED)

✅ Adapt design to a large and non expert audience

✅Very little text

✅ Story telling may involve more twists

✅ Voice

✅ Body language

✅ Larger images

✅ Videos



Identify the location and which tools you have available

How long can your talk be? How much time do you have to prep?

It will be a compromise:

The more you get confident with choices you have, the more efficient you will become in reaching your goal without wasting time.

✅Ask in advance.

✅Decide in advance how long you can spend on Introduction / Development / Conclusions.

✅Check the time during your talk to make sure you can adapt.

✅May ask for a warning 5 minutes before.

✅Give up on saying everything.

❌Complain about lack of time.

❌You are still in your Introduction after > X/3 minutes.

Time is up so I'll talk faster.

Time is up so I'll go fast on all the remaining 20 slides. If you are 5 minutes from the end and you still have several slides, going fast through plots/slides/caveats won't help, it just makes the audience more aware that you screwed up your talk. It shouldn't happen, but if it does, keep control, skip slides entirely and just say your final message. Make sure the audience understands at least that.

❌Chair tells me time is up but I'll continue anyway.

What do you want people to retain from your talk?

What are your keywords? Identify:

and make sure you explicitly give your message at the start, at the end, and whenever possible also within your talk.

Story telling

A standard outline would typically include: introduction, build-up and conclusions.


This is the part where you have to first capture attention.

❌Try to avoid very long sentences: you need to capture the attention now, not at the end of 100 words.

❌Avoid unnecessary citations (usually it's more interesting to know what you think than what someone else said, who knows when and who knows in which context).

Development and build-up


❌Don't conclude just because time is up. Enjoy your conclusions!


Fun can be good but is it funny?

Awkward situations you'd want to avoid:

❌As a speaker: you say a joke and laugh by yourself.

❌As an audience: laugh at a joke you recognise as bad, just to please the speaker.

Jokes can be:

Potentially good jokes: maybe some physics jokes / witty puns if it doesn't fall in the bad category (?) If you try, and someone gives you negative feedback, listen to them, apologise and try something else in the future.

How do you make your talk functional and interesting? How do you capture attention?

✏️ Text 📈 Images 💬 Speech

Audience will be mixed: some will hear what you are saying, some will prefer to read, some will concentrate on plots and visualisations. To reach everyone, you'll typically include all three of these elements. You will use your voice, you will leave the time to read some text, you will use a plot to illustrate your results.

Let's look at some tips to use your voice and design your slides.

When reading, text gives the main message. When speaking, things are much more difficult. Text is only a small part of your message.

Sometimes we think we said something but the message we gave was actually different. Many parameters contribute to your message.

Example: A: "Yesterday I ate a risotto"

B: "Oh, How was it?"

A: "Good."


Prosody does not refer to the text you pronounce but to how you say it.


can be high or low: it is related to how much air you use when you speak.

✅ Pick a person who is far away and talk to that person

❌ Don't talk to yourself


You can use a higher or lower pitch. Tone is related to contracting a muscle, the more tense it is, the higher the tone, like for a guitar.

❌avoid speaking always with a flat intonation.

Speech rate: (syllables/s)

❌avoid speaking always at the same rate: enhance contrast between what is more important and what is less important.


Have no fear of silences.


Are you aware of which one do you do? Try to be aware of them, and possibly reduce them.

Dominant or not?

Your voice will contribute to identify yourself in a role which is somewhere between dominant and sub-dominant.

Dominant: slow, many silences, thinking a lot about what you don't want to say; it can show confidence but also puts distance with your audience. Not advisable at the start of a talk. It may give the idea that you think you are in a higher role (and it may look like you put the audience in a lower role).

Sub-dominant: fast, many things to say, few silences.

Body language

Here are a few exercises using your voice.

Exercise 1.

Read the numbers choosing one intention among the ones in brackets:

12 34 23 75 (disgust, enthusiasm, resignation)

4 5 7 9 2 (sadness, fear, satisfaction)

Exercise 2.

Pronounce ‘Good morning' with different intentions and ask someone to guess which intention you sent.

Exercise 3.

Read this text

Massive neutrinos influence the background evolution of the Universe as well as the growth of structure. Being able to model this effect and constrain the sum of their masses is one of the key challenges in modern cosmology.

Massive neutrinos influence the background evolution of the Universe as well as the growth of structure. Being able to model this effect and constrain the sum of their masses is one of the key challenges in modern cosmology.

Massive neutrinos influence the background evolution of the Universe as well as the growth of structure. Being able to model this effect and constrain the sum of their masses is one of the key challenges in modern cosmology.

Exercise 4.

Try to pronounce the following sentence using one of the intentions listed below.

We'll talk about that tomorrow

Exercise 5.

The teacher said the detective is French.

Who is French? The teacher or the detective?

Changing pauses: The teacher said // the detective is French.

The teacher // said the detective // is French.

Changing intonation (without pauses):

The teacher said the detective is French.

The teacher said the detective is French.

The teacher said the detective is French (i.e. not a third person).


What's the most important thing you want that slide to say?

What's the second most important thing?

How much information do I need to say?


How are they different?


What can I delete?

Further reading:

What doesn't work with the slide below?


❌No Margins or white space

❌All main text

❌Different fonts

Let's see how we can improve it to make it more readable, even without removing text.

I can start by identifying what I want the audience to see first:



I can increase contrast between what comes first and what comes afterwards:



I can use icons and make it more fun. I can increase contrast further within the text, with bold/grey.


I can further reduce text if I wish, but the main issue was not ‘too much text'.

Icons made by Freepik, Nhor Phai, Icongeek26 from www.flaticon.com

How much text?

Not enough

Too much

Typically you will have more text for an audience with high expertise or in small locations; less text for an audience with low expertise or in a large auditorium.




Design changes over history: when you choose a font, implicitly you are also giving a message.


Sans-serif: less contrast, more contemporary, more geometric, more readable in slides.

Serif: more contrast, hints to tradition, history, sophisticated, emotional, closer to hand-writing. Usually less readable in slides with a lot of text.




Take the time to describe and explain your plot.

Describe: guide the eye of the audience through the plot: they have never seen it before! Go from outside to inside. What do you want the audience to look at?

Explain: why is it important? What's the message? If you can't find one, then you typically don't need the plot at all.


❌Unnecessary items (grids, boxes around legend, background shading...)

❌ Filling your slide with invisible plots. One visualisation is usually enough.

❌A plot is not a photo or an icon. It's not there to make your slides nicer, it's a visualisation of your results.



Icons can be found online: https://www.flaticon.com/

They are meant to be small and can be nice when used for itemising (instead of bullet points).

Usually the smaller the better, as they don't have many details.



Photos can be found online: https://freerangestock.com/ or you can use your own and make it more personal.

Photos can be used to highlight the title and main topic of the slide.

The larger, the better.

❌Avoid images at the bottom right of the slides: we tend to look from left to right and top to bottom. It looks like a patch on a slide which was already made.

❌Avoid illustrations that mimic a situation: hard to have the audience feel empathy for such a situation.






Some people like them very much, some other really don't.

They can be cool if they are high quality and you know what you are doing. Otherwise, I would avoid them.

Either there is a point to them, in making your message clearer or more fun, or they can distract the attention, especially in transitions.

There is no need to use all available colours just because they exist.


It has to be readable.

✅ dark background with light foreground

✅ light background with dark foreground


🔥Warm vs cool ❄️

Colours can have a general meaning, besides the one given by context.




Complementary colours are not necessarily a good choice:



If you don't have a style guide provided by your institution, and you are not an experienced designer:








Further reading:https://blog.indezine.com/2011/10/how-to-avoid-four-biggest-powerpoint.htmlhttps://24slides.com/presentbetter/pick-right-colors-presentation/

How are they different?

Much more difficult for both speaker and audience to manage and keep the attention. If you give a talk online as you would give it live, there is a high chance it won't be effective.