Avoid chartjunk in presentations: Three lessons from Tufte

After attending a course by Edward Tufte in Boston I was inspired to think about how I can create more effective visuals for presentations. When developing things like graphs and charts, there’s often a temptation to over complicate by adding what Tufte calls ‘chartjunk’. Tutfe has some key advice on how to avoid chartjunk which can be easily applied to presentation creation.

Edward Tufte is a Professor Emeritus of Political Science Statistics and Computer Science at Yale University and a pioneer in the field of data visualization. He has written four books on visual reasoning and data and has been described as ‘the Leonardo da Vinci of data’. In Tufte’s words, “The information is the method…” meaning that data on slides should speak for itself without interference. He coined the term chartjunk to describe the cluttered mess of information you usually see crammed into and around graphs. In his course, Tufte used examples from his books and popular media to explain how the ways in which we communicate data has a huge influence on how that data is understood. There are three key lessons I brought away with me that we currently apply in our presentation creation to improve information transfer and more effectively engage our clients’ audience.

Scales of measurement

Though Tufte speaks about avoiding chartjunk he also emphasises that it’s important to give your audience all the information they need to quickly interpret your data. One of the first things Tufte mentions in his book is the importance of clarifying scale in diagrams. He mentions that often historical texts, (including Markus Bloch’s Ichthyologie, which contains illustrations of 216 different fish!) fail to designate a scale for their subject matter, so make it impossible for the reader to interpret a crucial piece of information. Simply including a reference for scale, such as a “universal ruler”, Tufte writes, could dramatically improve information transfer.

How big are these fish?

Edward Tufte’s concept is easily applicable to PowerPoint. For example, when talking about products, scale holds significant explanatory weight. Showing your audience a product in context may be incredibly valuable for sales. If you’re including imagery of products in your next presentation, try to show them in the end user environment instead of floating in space on a white background. This more accurate imagery will allow your audience to gain a better understanding of how your products are used and help them imagine themselves as users.

Labels

Another piece of Edward Tuft’s advice you can apply to PowerPoint presentations is effective labelling. Tufte believes that having a separate key adjacent to a graph takes away from understanding and creates clutter. He explains that having information set up this way causes confusion and failure of information transfer because the audience has to keep looking back and forth between the key and the information to interpret the data. Tufte uses an example of two identical photos of dogs. In the first the dogs are clearly labelled with their names next to them in large print. The second has the names in a separate key with letters on the dogs corresponding to the labels. The lesson here is that the former is easier for everyone to read, while the latter adds chartjunk. The key over complicates a straightforward concept.

We know exactly who is a Good Dog!

This lesson is key when creating graphs and charts for a presentation. When possible, you should eliminate keys and instead label the image or graph itself. This will help your audience interpret your data quickly and they won’t get tired of trying to “translate” your data and give up all together. Read more about PowerPoint graph mistakes to avoid on our blog. You should allow the data to speak for itself – one of the leading themes in Tufte’s work.

Replacing text labels with images

This final lesson gave me food for thought. Tufte argues that sometimes text labels are more effective as images. He gives an example of a graph that originally used text labels for different animals to illustrate their position on a brain mass vs. body mass chart. He then replaces the text labels with imagery of the different species, and almost immediately the chart is easier to grasp.

Without written labels the viewer can group animals visually and quickly notice patterns like the cluster of dinosaurs to the right or the group of ape-like creatures to the left of the trend. Using a visual rather than verbal representation allows the viewer to notice these patterns themselves almost instinctively. They can build associations with the visuals, increasing understanding and retention. In PowerPoint, using imagery in this way means you have to ditch live graphs and recreate your graphs with PowerPoint shapes. This is pretty easy and we cover how to do it in our Advanced PowerPoint Training. Click to learn more about working with live graphs in PowerPoint.

This method won’t work with all data, but can really pack a punch when used well.

I agree with Tufte, data is compelling, so graphs and charts can be a great asset to a presentation. However, there are ways you can make data more easily understandable to your audience. To avoid chartjunk in presentations the content on your slides should be as concise and effective as possible. This means building context, getting rid of text labels, and adding more visuals. If you’re interested in learning more about how Edward Tufte’s ideas could improve your presentations, I’d recommend picking up a copy of Beautiful Evidence (or one of his other publications) – it’s a great resource. By applying even a few of his teachings to your next presentation you can ensure better audience comprehension and engagement, driving results.

For more data visualisation inspiration check out our blog post on how to improve your data visualisation or start with the graphs and charts basics with our free resources!