Back to Blog

Use an assertion-evidence structure in your slides

Jun 12, 2014

Yale’s Edward Tufte, a preeminent specialist in data visualization, vehemently criticized PowerPoint presentations, noting that it “promotes a cognitive style that disrupts and trivializes evidence” (Tufte, 2003). From experience, thinking about the dozens of presentations I sat in over the past few months, I agree that most weren’t optimally visually supporting the presenter’s point. Yet, that doesn’t mean we are doomed.

Joanna Garner, Michael Alley and their colleagues contend that writing the summary of each slide in its tagline and using the body of the slide to provide evidence supporting the summary can significantly improve the audience’s understanding and recollection (Garner 2011).

Use an assertion-evidence structure

The approach—called the
assertion-evidence structure—isn’t new. Alley traced its use back to Hughes Aircraft in the 1970s and Lawrence Livermore National Laboratory in the 1980s (Alley, 2013). It has also been widely used by many strategy consultants for at least the last 25 years (and that’s where I had my first glimpse of it).

[IMAGE MISSING: assertion-evidence.png]
The assertion-evidence structure calls for a self-contained tagline that summarizes the main idea of the slide with the body providing evidence supporting that summary

Communication consultant Jean-luc Doumont agrees that the approach is useful; for him the title of effective slides states the message—that is, what the presenter wants the audience to remember. As such, taglines of effective slides are short sentences and, therefore, include a verb (Doumont, 2005).Studies empirically support that the structure is effective. Garner and her colleagues reported that, in their study, it helped participants learn more complex concepts than traditional PowerPoint slide formats (i.e., topic-subtopic slides) (Garner, 2011). In a different study, Alley and his colleagues found that the approach promotes retention (Alley, 2006).Overcome obstaclesTransitioning to using an assertion-evidence structure can present some challenges. At Accenture, my boss periodically had to point me to slides where I had returned to my old ways. And looking at my students’ presentations, I appreciate how we are all conditioned not to use the assertion-evidence structure. In fact, the conditioning is evident opening PowerPoint’s (or Keynote’s) templates: slide titles are pre-set to be titles, not sentences, and therefore need some tweaking around.Yet transitioning is not complicated, especially if you start preparing your presentation from the top-down: Write in one paragraph the story that you want to tell in your presentation. Then, cut out this paragraph into “idea capsules” each one being 10 or 20 words long. Then distribute those in the taglines of your slide and, voilà, you are now part of the club. It’s at least worth a try, isn’t it?ReferencesAlley, M., et al. (2006). “How the design of headlines in presentation slides affects audience retention.” Technical communication
53(2): 225-234.Alley, M. (2013). The craft of scientific presentations, Springer, p. 115.Chevallier, A. (2016). Strategic Thinking in Complex Problem Solving. Oxford, UK, Oxford University Press, Chapter 7.Doumont, J.-L. (2005). “The cognitive style of PowerPoint: Slides are not all evil.” Technical communication
52(1): 64-70.Garner, J. K., et al. (2011). Assertion-evidence slides appear to lead to better comprehension and recall of more complex concepts. 118th ASEE Annual Conference, Vancouver, B.C.Tufte, E. R. (2003). The cognitive style of PowerPoint, Graphics Press Cheshire, CT.

Arnaud Chevallier