Visual aids are an important factor in a successful engineering or science presentation, and as a speaker, you should give careful consideration to your approach to visual aids.  Unfortunately, many presenters rely on the default settings provided by PowerPoint to create slides for their presentations. Typically, this approach results in tiresome slides heavy with bulleted text and perhaps an occasional image.

As a presenter, you should consider if this traditional slide design is in fact the best method for communicating scientific information. What research exists that supports the effectiveness of much bulleted text and the occasional image for the communication of scientific information? Since slides are omnipresent in technical presentations, this question deserves some consideration.

Here, we strongly advocate for the use of the Assertion-Evidence slide design as a more effective alternative to the traditional bulleted text approach.  Research has shown that the Assertion-Evidence slide design is more understandable, memorable, and persuasive than the traditional design in presenting scientific information. The Assertion-Evidence slide design is characterized by a concise, complete sentence headline (no longer than 2 lines) that states the main assertion of the slide (i.e. what you want the audience to know as a result of the slide) and the body of the slide consists of visual evidence for that assertion (charts, graphs, images, equations, etc.).

You are strongly encouraged to research and learn more about the Assertion-Evidence design. More details are not discussed here because all facets of this design are covered in excellent depth on a partner website “Rethinking the Design of Presentations Slides” (first Google listing for the search term “Presentation Slides”).

Even if you are skeptical, challenge yourself to learn about and utilize this design for your next presentation. We believe that you will find that your talk is more focused and that great potential exists for your audience to gain more understanding about your subject matter.

Note that it will likely take you longer to create slides when using this design. An inherent benefit of the headline assertion on each slide is that it forces the presenter to articulate the purpose of the slide and to consider how that slide fits into the overall argument—this can take some time. However, this is time well spent as it typically results in a more focused presentation.

So, how should you get started? It is critical that you begin with the template (a .ppt file) that is provided on the website “Rethinking the Design of Presentation Slides.”  This file can be found on the left side of the page under "Assertion-Evidence Templates." This will help you to overcome the weak defaults of PowerPoint. Additionally, here is a summary of the recommendations for style, typography, and layout of Assertion-Evidence presentation slides.


Guidelines for Assertion-Evidence Slides [Alley, 2003]




1.  Begin each body slide with a sentence-assertion headline that is left justified and no more than two lines

2.  Support the assertion headline with visual evidence: photographs, drawings, graphs, or words and equations arranged visually



1.  Use a bold sans serif typeface such as Arial or Calibri

2.  Use 28 point type for the headline, 18–24 point type for the body text, and reference listings in 14 points

3.  Avoid setting text in all capital letters, in italics, or in underline



1.  Keep blocks of text, including headlines, to one or two lines

2.  Keep lists to two, three, or four items

3.  Be generous with white space, especially between text blocks and graphic elements within the slide



Examples of Assertion-Evidence Slides




Alley, Michael (2003). The Craft of Scientific Presentations. New York: Springer, p. 116.

Miller, Genevieve (2008). Presentation given in CAS 100A for Engineers. Penn State.


It is our goal that you will choose to adopt the Assertion-Evidence slide design as a successful strategy to make your technical presentations immediately more effective. 

Tips for Using Slides

Now let’s discuss a few tips for the use of slides in your presentations:

1.    Overcome PowerPoint's weak defaults.  Begin designing your slides with the template provided by the website “Re-thinking the Design of Presentation Slides”.  The template can be found on the left side of the page. Don’t underestimate the importance of this template in trying to overcome the weak defaults of PowerPoint.

2.    How many slides?  Many presenters want to know how many slides they should have.  You should aim to have no more than one slide for every 1-2 minutes of presentation time (20 minute talk, approx. 10 slides recommended). If your number of slides exceeds this, you risk not providing your audience with enough time to absorb the information from your slides.

3.    Discuss your slides.  It is important that you directly discuss and incorporate your slides into you talk.  Don’t assume that your audience will just figure it out for themselves. Many presenters will click through slides without directly mentioning and discussing their content. You are essentially the tour guide about your topic during the presentation—the slides are an important stop on that tour!

4.    Practice with the equipment.  Make sure you know how your slide advancer works. It is distracting to the audience if you are fumbling with the equipment and it will only serve to make you more nervous. Just arriving a bit early to the room that you are presenting in and familiarizing yourself with the environment and equipment can eliminate many of these issues.

5.    Practice with your slides.  It is damaging to your credibility as a presenter if you are clicking back and forth “searching” for the slide that you want to discuss. You should know precisely where and when each slide is coming in the presentation. A good tip is to put a Post-It note on your computer that lists the numbers of your important slides. This way, if you do need to jump to a slide, you can just type that number into your computer, hit “Enter,” and the screen will jump right to that slide. This is much more professional that clicking back through 12 slides during a Q & A session because an audience member had a question about a slide that appeared early in the talk.

6.     Manage the environment.   Be sure to take control of the lighting so that your slides can be seen to their best advantage.  Many times the lights on top of the screen are left on and the resulting glare makes slides look washed out and difficult to see.

7.    Use the laser pointer sparingly.  If you have shaky hands, the laser pointer only serves as beacon emphasizing your nerves to the audience. If precision of location is important, It might be more effective to use your slide software (animate a circle or arrow) to emphasize the area that you want to highlight for your audience. An old-fashioned pointing stick can be effective also.

8.    Slides aren't always neccessary.  Perhaps the most important thing to know when using slides in a presentation is when to turn them off.  There is no rule that says that it is a good idea to be show slides during the entire talk. Slides are not always the best medium for your information and you should get into the habit of asking yourself, “Is a slide necessary?”. For example, if you are discussing a personal experience or observation, that information might be more effectively communicated without a slide. Additionally, your slides should not be visible unless they are relevant to what you are currently discussing in your talk. When you finish with the point discussed in a slide, choose to blank the screen so that the audience focuses entirely on you. Blanking the screen can be one of your most powerful tools because it refocuses the attention of the audience onto you.  

9.    Slides aren’t the only option for visual aids.  Don’t be afraid to think outside the box and consider other types of visual aids such as demonstrations and videos. We can see great examples of how these are used effectively with our model presenters. Scott Fishbone uses a flashlight demonstration to great advantage when highlighting the differences between xenon and halogen lighting. David Gallo uses video footage to provide a definite “wow” factor to his presentation. Would his use of visual aids have been nearly as effective if he would have chosen to show still images of the sea creatures? Definitely not. Of course, it is essential that you practice and prepare to smoothly incorporate alternative visual aids into your presentation.

 Video Examples for Visual Aids 


Example #1

David  Gallo  , "Underwater Astonishments"



Example #2

Genevieve Miller, "The Role of the Bioreactor in Breast Cancer Research"


Discussion of Example #2

This presentation has many strengths (such as structure), but here we will focus on this presenter’s excellent use of visual aids.  It is clear that this presenter has thought critically about how to best communicate her technical information visually to the audience.  She has very carefully crafted headlines on each slide that communicate the key information to her audience, and the body of the slides contains excellent images that illustrate the information from the headline visually.  As you review each slide, notice the strong relationship between the headline and the corresponding visual evidence.  Had this presenter employed the traditional bulleted list design of slides, the audience would have not gained nearly as much understanding of this presenter’s research. 

Slides 1 and 2 (1:30)

These slides clearly introduce the audience to the key terms and conditions that they must know in order to understand the function and limitations of the typical culture system.  The illustration of the macromolecules and waste products gives us a concrete representation of the dramatic shift that occurs in the environment when the medium is changed.  Notice how the headlines of each slide provide a clear focus for what the listener is to obtain from the slide.

Slide 3 (2:45)

The placement of this slide in the presentation is critical.  It is natural that the audience would want to see a picture of what an actual bioreactor looks like, but it is important that the speaker provides this information at the right time.  Had she showed this slide in the introduction when she first mentions the bioreactor, the audience would not have had an appreciation for what goes in inside a cell culture system, so they would not have gotten as much out of her explanation of the different compartments in the bioreactor.  Now that we have already seen the illustration from Slides 1 & 2, we understand the functions of those compartments.  Moreover, we are now ready to move on and understand the unique properties of the bioreactor.  Had she showed this slide after she discusses the unique properties of the bioreactor, it would not have had as much impact because it would be coming too late.  Finally, notice her use of the red circles to highlight the compartments as she is discussing them.  This is an effective method of indicating important areas on an image rather than using a laser pointer.  A laser pointer would have been much more distracting in this case. 

Slides 4 and 5 (3:37)

These are perhaps the most memorable slides of the presentation—these are ones that the audience is likely to talk about even after they have left the presentation.  This simple, yet powerful animation allows the audience to see the unique function of the bioreactor, and the speaker is able to highlight a key part of the research which is how the stability of the cell environment is achieved.  Because of how memorable these images are and how clearly they communicate the relevant information, it is likely that an audience who did not know much about the topic would be able to explain the basic qualities of the bioreactor weeks after seeing this talk.  You will want to consider in your own presentations what type of images you might be able to provide that will “stick” with the audience.

Slides 6 and 7 (4:52)

These slides begin the part of the talk where the presenter is discussing the results and application of the work with the bioreactor.  Again, because this information is represented visually, rather than through text and bulleted lists, it is much more likely to be remembered by the audience.  Also, the speaker does an excellent job of walking the audience through the images and pointing out the specific parts that they should notice.  The images on Slide 7 are very compelling, and the labels that are applied below each one are helpful in distinguishing what is being seen.  This is an example of the appropriate use of text in the body of the slide. 


Example #3


Scott Fishbone, "Advocating for Xenon Headlights"


Discussion of Example #3 

This presenter’s topic lends itself to highly visual evidence since it deals with light, and this presenter recognizes and seizes the opportunity.  As a result, the visual aids are a crucial element in the success of this presentation.  This talk is significantly more engaging because of the use of visual aids.  The key argument that this speaker is trying to make with his presentation is that xenon headlights are superior to halogen headlights.  The proof of this assertion lies in a comparison of performance between the two technologies, and this is the strategy that the speaker utilizes when designing his visual aids.  

Slide 1 (1:00)

This speaker begins his presentation by establishing the importance of proper headline function by discussing the problems that occur in part because of poorly performing headlights.  The headline of this slide summarizes the key problems and the picture is one that could stir emotion and raise concern within the audience.  Perhaps some audience members have had an experience very similar to the one represented in the picture or even just visualizing something similar happening to them personally is certainly enough to raise concern.  This is effective because it invests the audience in the importance of improving these problems. 

Slide 2 (1:42)

This slide serves the purpose of emphasizing the main assertion of the talk.  This is accompanied by an image that provides a visual anchor for the assertion.   

Slides 3, 4, 5, and 6 (2:06)

This series of slides uses images of comparison very powerfully.  Each slide focuses on a direct comparison of various characteristics between halogen and xenon headlights.   The main assertion of the talk is to prove the superiority of xenon headlights.  The speaker provides much evidence for this assertion by showing the major difference.  There is truth to the saying, “Seeing is believing.”  By showing the image comparisons as he analyzes each performance characteristic of the lights, the audience is able to make the judgment for themselves after analyzing the visual evidence.   Another presenter might have just chosen to present the comparison with a table of data (e.g.  amount of lumens, percent of peripheral area that receives light, etc.).  Imagine how different this presentation would have been if that approach had been taken!  Fortunately, this presenter uses his slides to his maximum advantage, and as a result, his presentation makes a compelling argument for the advantages of xenon headlights.   

Demonstration (3:40)

This is perhaps one of the most compelling parts of this presentation because the audience is able to see firsthand the difference between the two technologies, and the reason that it succeeds is because the comparison is so striking. This speaker stepped “outside of the box” in terms of using a visual that was not a slide, and it was a great success. We are so conditioned to use slides as our only visual medium, so we can forget that there are often much better ways to visually represent information and ideas. Demonstrations can be incredibly effective because they get the audience involved and make them feel a part of the action because they are witnessing something firsthand, instead of seeing it on a slide after it has occurred.  

Example #4


Jeff Rayl, "The Future of Solar Power"


Discussion of Example #4

This presenter’s visual aids are a strength of this presentation.  There are two elements that stand out about this presenter’s use of visuals.  First, this presenter uses a variety of different types of visual evidence, which makes the visuals dynamic and will appeal to a variety of audiences.  Secondly, this presenter incorporates his visuals very well.  He discusses them specifically and indicates to the audience the key areas that they should notice in each image.  Let’s look at each slide individually and discuss its function in the talk:

Slide 1 (2:04) 

This first visual is used to support the speaker’s assertion that solar energy’s abundance makes it the best candidate for our energy needs.  The image chosen by this speaker is highly effective because it is so striking.  The audience is able to see very clearly the different colors that delineate the different regions of exposure to solar energy, and the speaker incorporates this visual well by pointing out the key colors of orange, yellow, and green.  Furthermore, he emphasizes that most of the highest populations are contained within the high energy region which supports the argument that he is making and the listener is able to verify this through this visual image.

Slide 2 (4:55) 

This was a well-chosen visual because the chart clearly shows an upward trend, which is important to the argument that the speaker is making.  Additionally, this chart provides a point comparison between the original technology of crystalline silicon and the new technology of thin film.  This is a key piece of evidence as the speaker argues that the coming technologies are becoming more and more viable and efficient.

Slide 3 (5:41) 

At this stage in the presentation, the speaker is explaining the new technology developments.  This slide serves to engage the interest of the audience because they can see how these technologies would actually look and function on a home.  Note the use of the animation “appear” for the second image.  This is a good choice because the speaker didn’t want to focus on that image right away, so it made sense to bring it in when he got to that point in the talk.  There are very few scenarios in technical presentations when it is wise to use an animation type other than “appear”.  Typically, the use of other types of animation only serves to distract from the content of the presentation and should be avoided.

Slide 4 (7:20) 

The headline of this slide is particularly strong because it focuses the audience directly on the key assertion of this slide—that the new technologies are using less material while being more efficient.  The graph provides evidence for this assertion, and the speaker points out that amorphous silicon (a-Si) performs markedly well in this area.   




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