Determining what kind of visuals to prepare to accompany a presentation is no mean task. Images are often appropriate, but at other times your purpose, message, and audience require data slides. Preparing these slides according to reliable guidelines helps ensure their accessibility and precision—and thus their effectiveness.

But other practices concerning data visualization can also facilitate the at-a-glance comprehension that clarifies and emphasizes messages in a presentation. These considerations include audience awareness, focused content, and descriptive titles or captions.


Cognitive Load Theory (CLT) explores the demands made on working memory when the brain is processing new information. One CLT principle is that although the working memory is necessary for learning, understanding, reasoning, and problem-solving, it has a finite capacity for simultaneous processing.

Information entered into the working memory must be processed in order for learning or understanding to occur. Thus a visual that introduces too much information increases the amount of cognitive processing required. Like the sorcerer's apprentice in Disney's Fantasia, the working memory cannot handle excess. Its attempt to do so reduces comprehension, and a similar reduction occurs when irrelevant information floods the boundaries of working memory.

As you prepare data visuals to accompany your presentation, be aware of the brain's limited processing capacity. By working within it, you'll improve listeners' ability to comprehend the data you present in support of messages.

Here are three ways to work within the boundaries.


Use what you know about your audience to help you determine what information is likely to be new or most troublesome to its members. Assess their current knowledge so you can design visuals that more smoothly integrate new information. If it's possible, attach that new information to something the audience already understands, something pertinent that is also a part of your message. Consider audience perspectives so you can identify and address issues they may have with your data. In short, do everything possible to facilitate listeners' comprehension.


Include in a presentation visual only the data communicated by its title. Every part of the visual must be relevant, focused on the promise carried by its title. Omit anything extra or extraneous—everything must relate directly to your message. When it does, your message dominates the slide.

In addition, it's far better to provide several simple, focused graphics in presentations than one made complex by too much content.


Emphasize messages by using editorial titles, titles that present the conclusion or point drawn from the data. Such descriptions provide orientation to and context for the message. For instance, instead of the title "Market Share," try "Market Share Increased in All Segments except South, 2010-2012."

Avoiding cognitive overload in the design of a visual also extends to the selection of graphics best suited to particular purposes. Our next Speak Previews® will look at those.