1 Bullets on the Wall

Bullets on the wall are slides that present a detailed outline of the talk as bullet points that are projected on the screen/poster board. In the days before slides and screen protectors, speakers commonly used an outline as a prompt to help remember the key points of their talk. A written outline of the ideas that you want to cover in a talk remains a useful aid to a complete and coherent presentation, especially if you are speaking without slides. However, projecting a detailed outline of your talk on the wall, and then talking through the points bullet by bullet, or even worse, reading them directly to the audience, is a misuse of the verbal presentation format and a huge turnoff to the audience.

Do you like attending oral presentations where bullets are projected on the wall and the speaker reads them to you? When a Fortune 500 company has a new product to advertise, do they use a bulleted list to communicate its attributes to potential customers? Of course not. We are drawn to engaging speakers and engaging presentations. One of the roles of a scientist is to communicate her/his findings and ideas so that a broader audience considers them, so it affects the audience’s understanding and impacts serious discussions.

A verbal presentation is an opportunity to leverage a range of your interpersonal skills to communicate your ideas with your audience. For centuries, people have made compelling oral presentations without visual aids. The slides that support an oral presentation should be constructed to reinforce your communication objectives, so it helps the audience understand the ideas you are presenting. Bullets after bullets after bullets bore an audience. This is a recipe for losing the audience’s attention and failing to meet your communication objectives (Figs. 9.1.1 and 9.1.2).

Fig. 9.1.1
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Opening slides for an influenza surveillance talk with too many bullets

Fig. 9.1.2
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An alternative opening slide for an influenza surveillance talk that communicates to the audience why this is a compelling issue

2 Using Sentences for Bullet Points

Bullet points should be terse summaries that help the audience follow your key points. They should not be full sentences or paragraphs that you read. Full sentences and paragraphs are appropriate for scientific writing, but it is mind-numbingly boring to have full sentence after full sentence projected with the speaker reading the sentences to the audience. The average audience member can read such sentences three to five times faster than the presenter can speak them, so this is not an efficient method to communicate. It is a misuse of a verbal presentation opportunity.

Posters are meant to be read, and so somewhat longer lines of text can be used than in a verbal presentation, but ideas that break down into sections should still be presented as brief bullet points so people can quickly grasp the structure of the ideas (Figs. 9.2.1, 9.2.2, 9.2.3, and 9.2.4).

Fig. 9.2.1
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Sentences making minimal use of visual organization of ideas

Fig. 9.2.2
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Ideas organized as bullets. This would also accommodate a nice picture of a clean toilet which would further enhance communication

Fig. 9.2.3
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Paragraph-like bullet from a draft poster

Fig. 9.2.4
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Information recast as quick-to-read organized bullets

3 Too Much Space Between Bullets

Oftentimes, PowerPoint inserts substantial space between lines of text. This can occur both as too much space between lines within a bullet as well as too much space between bullets. All of this white space reduces the amount of space for communication and forces smaller font sizes that becomes difficult or impossible to read, especially from the back of the room.

These spacing issues can be addressed by using the paragraph features of PowerPoint. Set the line spacing to single, and make spacing before and after small (e.g., <6 pt.). Another strategy to modify space between bullets is to insert a line with a single letter of text. Color the text the same color as the background, and adjust the font size to something small that optimizes spacing (Figs. 9.3.1, 9.3.2, 9.3.3, and 9.3.4).

Fig. 9.3.1
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Lots of white space not well used that limits font size

Fig. 9.3.2
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Reorganization of slide redistributes white space to better group and communicate ideas. Animation features could be used so that the top of the slide appear first and the data analysis section appears when the presenter clicks

Fig. 9.3.3
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So much space between the bullets that the list stretches across two slides

Fig. 9.3.4
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Same bullets with reasonable spacing between fit on a single slide

4 Using Bullets Without Hanging Indents

Bullets help to format text so that it is clear there are a series of points. They improve readability of narrative. It is easiest to see the difference between points when a hanging indent is used on subsequent lines so that the separation between ideas is clear. In addition, a slightly larger spacing between points in contrast to lines within points further makes this separation easier to see and read (Figs. 9.4.1, 9.4.2 and 9.4.3).

Fig. 9.4.1
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Bullets Without Hanging Indent (the Common Error)

Fig. 9.4.2
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Bullets with Hanging Indent

Fig. 9.4.3
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Bullets with Hanging Indent, Single Space Within Points, with 1.2 Spaces Between Lines, and a More Horizontal Layout

5 Chart Junk

In his classic book, The Visual Display of Quantitative Information, Edward Tufte defines chart junk as visual elements in charts and graphs that are not necessary to comprehend the information represented, or that distract the viewer from this information. Among the worst promoters of chart junk are institutions that want all slides to have a common look that advertises the institution. These objectives run counter to clear communication. Clear communication will better promote a scientist and their institution’s reputation compared with tacky backgrounds that obstruct and detract. Clear, large, and simple is the most effective pathway to clear visual communication. If your institution insists on a stylized template, we recommend using it only on the opening and closing slides (Figs. 9.5.1 and 9.5.2).

Fig. 9.5.1
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A slide from a presentation using a template requested from the study funder designed to give credit to funders and a uniform look to the presentation

Fig. 9.5.2
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A cleaner presentation of the slide with chart junk and extraneous information removed to permit attention to the key communication objectives

6 Using Three-Dimensional Chart Features as Decorations

Figures are used to connect to the visual centers of human perception and so improve communication of your quantitative results. Adding three dimensions to charts adds complexity. This complexity should only be invoked if it improves communication of the data. Otherwise, this three-dimensional imagery is chart junk (Error 9.5) that risk distracting the audience. Strive for minimalist elegant images that communicate without distraction (Figs. 9.6.1, 9.6.2, and 9.6.3).

Fig. 9.6.1
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Three dimensions used as uninformative chart junk

Fig. 9.6.2
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Simpler cleaner chart

Fig. 9.6.3
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Three-dimensional features used to support data communication

7 Using a Pie Chart

For a scientific presentation, simple pie charts are best avoided. It is safe to assume that a scientific audience understands percentage without having it illustrated. That is, they don’t need an illustration to appreciate that 25% is one quarter of a pie.

Pie charts made using the default features of PowerPoint are particularly bad. In the PowerPoint pie chart, the reader has to jump back and forth between the pie and the legend to sort out what the particular proportion represents. This requirement that the reader decodes adds another cognitive task that detracts from simple communication. It invites the audience to focus attention on decoding your graphic at the expense of listening to what you are saying. If there is a compelling reason for a pie chart, use labeling that avoids a legend (Figs. 9.7.1 and 9.7.2).

Fig. 9.7.1
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Default pie chart from PowerPoint. It is both underinformative and requires decoding

Fig. 9.7.2
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Easier to interpret visualization of data from Fig. 9.16. The labels are right next to the numbers. No decoding required

An exception to the rule of avoiding a pie chart is when a comparison between two groups or a breakdown of a subgroup of a pie provides a useful illustration that engages the audience’s visual understanding to interpret patterns in the data (Figs. 9.7.3 and 9.7.4).

Fig. 9.7.3
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An illustrative pie chart that effectively embeds additional meaning and communicates effectively

Fig. 9.7.4
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A comparative pie chart that supports a visual understanding of a distribution

8 Using Vertical Bars When Horizontal Bars Would Communicate Better

Vertical bar charts are commonly used default formats in PowerPoint, but they are often not the best way to present data. If a useful description of the characteristic being presented is long, it is difficult to read in the constrained space or at an odd angle at the bottom of a slide. A horizontal bar allows more space and larger font to facilitate quick communication (Figs. 9.8.1, 9.8.2, and 9.8.3).

Fig. 9.8.1
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Vertical bar chart with long labels. Note that the titles do not align intuitively with the bars. Our eyes are not accustomed to reading across odd angles

Fig. 9.8.2
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Vertical bar chart with multiline descriptions. These are often small and difficult to read

Fig. 9.8.3
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Simpler, easier to read horizontal bar chart

PowerPoint is quirky. In many versions of PowerPoint, the order of appearance of the horizontal bars is directly counterintuitive. That is, when you construct the data table, the first variable you enter displays at the bottom of the chart, and the bottom variable is at the top. You can simply reverse the order in the data table to have it present according to what aligns best with your communication objectives.

9 Copying a Manuscript Figure Instead of Developing a Custom Figure

Constructing high-quality slides to support a verbal presentation requires considerable thought, creativity, and time. It might save time to use figures developed by others in your own presentation. Especially when you are reporting information from other research groups, it is quite tempting to copy directly from their manuscripts or, if you have access, to their slides. The drawback to this approach is that visual presentations used for one speaker in one context often have a somewhat different role in your own presentation. Copying and pasting someone else’s work (even if appropriately attributed) is often not the best way to achieve your communication objective.

Each slide should be integrated with the narrative and communication objectives of your presentation and should be designed to help the audience succinctly understand your ideas. A visual presentation is quite different from reading a manuscript. Figures or tables in the manuscript can include more detail because the reader can take the time to work carefully through these details. By contrast, the pace of an oral presentation is quicker, and so the supporting information should be presented more simply in a clear format that the audience can intuitively grasp. If you find yourself saying “I apologize for the messiness of the slide, but I want to focus on this one issue . . .” or “This is hard to read, but. .. ,” this is a message to yourself that the slide needs to be revised. Remove the messiness. Clearly communicate the one issue to the audience and jettison the apology (Figs. 9.9.1 and 9.9.2).

Fig. 9.9.1
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Slide developed by lifting a table from a manuscript

Fig. 9.9.2
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Custom graphic derived from the table to communicate key messages to an audience. Note the elimination of most of the numbers, the removal of the confusing nonstandard abbreviation, yet noting the countries that were actually included

10 Photos with an Unnatural Aspect Ratio

Digital photography allows us to insert engaging photographs into our presentations. Often, to make the text fit more neatly with the photograph, we adjust the size of the photograph, but sometimes inadvertently we also affect the aspect ratio. The aspect ratio is the ratio of the width to the height. If the ratio of the width to the height is changed, the photograph appears distorted. This is particularly common when using PowerPoint and resizing the image by clicking and dragging. Below is the same photograph with three different aspect ratios (Figs. 9.10.1, 9.10.2, and 9.10.3).

Fig. 9.10.1
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The photographic subjects have been squeezed. That is, the horizontal aspect ratio is too small compared with the vertical

Fig. 9.10.2
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Here the photograph has been stretched horizontally

Fig. 9.10.3
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This is the photograph as taken by the camera

Changing the aspect ratio distorts the picture and makes readers wonder whether the photographic subjects are oddly disproportioned. To make a photograph fit within a space, consider careful cropping and selecting the right size, but don’t change the aspect ratio. You may also need a photograph with a different orientation. When combining text and photographs on a PowerPoint slide, vertically oriented photographs generally use the space better and are easier seen from the back of the room. Encourage your field team to compose photographic subjects that work well with a vertical orientation.

One way to avoid distorted aspect ratios is to use the insert function on MS Word or MS PowerPoint to directly insert the file rather than using copy and paste. You can then adjust the size of the photograph by right-clicking on the photograph, select size and position, ensure that the “lock aspect ratio” box is checked, and then change the size of the photograph by incrementing the height or width using the arrow keys.

11 Too Many Photographs on a Single Slide

Context is critical for communicating public health scientific results. Many people in the audience will never have visited communities similar to where your study was conducted or understand the local practices and conditions. Photographs can communicate to an audience the situation that gave rise to the issue of public health interest and the people who are at risk through visual pathways that complement spoken description and written text.

A common saying asserts that a picture is worth 1000 words. Especially in an oral presentation when timing is strictly limited, an extra 1000 words to communicate your study is a huge asset. However, we would slightly modify the saying. That is, one good picture is worth 1000 words. A good picture illustrates your point and is easily seen by your audience. A plethora of pictures risks being distracting because they are too small to see by the half of your audience who are sitting in the back half of the room. Moreover, multiple pictures mean multiple messages, and so the audience may be focusing on trying to figure out what is in each of the tiny pictures, rather than listening to your verbal presentation (Figs. 9.11.1 and 9.11.2).

Fig. 9.11.1
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Slide cluttered with too many photos

Fig. 9.11.2
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The photograph is large enough that the audience can see the fieldworker measuring the child’s upper arm

12 Fieldworkers as the Dominant Subject of Photographs

We cannot usually afford to include professional photographers on our field teams to capture images of the context where we work. Consequently, we depend upon fieldworkers or other members of the study team to take pictures that can be used to communicate context to our audience. Fieldworkers, however, are often particularly interested in pictures of the field team. Although this is occasionally a useful complement to a verbal presentation, photographs that illustrate the conditions as experienced by the target population are generally much more useful. We recommend specifying to the photographers on your team the photographic subjects that you are particularly interested in. Verbal presentations are often presented to audiences who have never been in the country or seen the conditions where the work was conducted, so photographs that provide an evocative illustration of these contexts are particularly useful to improve audience understanding (Figs. 9.12.1 and 9.12.2).

Fig. 9.12.1
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Photograph of a water treatment device affixed to a hand pump surrounded by study personnel and men in the compound. This staged photograph displays involved workers, the device, and some information on context but does not show the device actually being used, nor does it include women who are the primary caretakers of household water

Fig. 9.12.2
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This photograph shows women working with a compromised water supply near an open drain. It illustrates the cramped surrounding and the proximity of supply water to contamination

13 Including a Final “Thank You” Slide

Having your final slide say “Thank You” (presumably to the audience for their attention), often accompanied by an illustration that is irrelevant to the theme of your talk, is common in some contexts. Such slides are less common in an international scientific forum. Indeed, they often appear out of place. The gratuitous graphics distract from the major communication message of your talk. Drop such slides. Your final slide should either be acknowledgments or conclusions (Fig. 9.13.1).

Fig. 9.13.1
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A final “Thank You” slide should be left out of the presentation

14 Failure to Separate Ideas in a Multilined Title

When typing a sentence, after producing sufficient text to fill a line, the next word appears on the next line. This works fine for sentences but is suboptimal for titles. Titles are an integral element of the visual presentation of your ideas. By thoughtfully dividing the title into natural parts, the audience can more quickly understand your message (Figs. 9.14.1, 9.14.2, 9.14.3, and 9.14.4).

Fig. 9.14.1
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Multiline title running to the end of the line

Fig. 9.14.2
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Better title split by ideas

Fig. 9.14.3
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Default splitting of title

Fig. 9.14.4
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Improved title with ideas grouped together