…Well, in plan communications and Gantt charts, it does.

Size, when used as an attribute to denote meaning in data visualization, will likely force our brain to look at the largest items first. In her book, Storytelling with Data, Cole Nussbaumer Knaflic tells us, “Relative size denotes relative importance.”

Size is just one of the “preattentive attributes,” or visual clues, that tell our brain where to look. When employed correctly, as Nussbaumer Knaflic suggests, these attributes can be used not only to tell our audience where to look first, but also to create a “visual hierarchy” that will allow us to communicate layers of data to our audience in a natural flow. The hierarchy allows us to better tell the story of the data, even in a single visual.

The preattentive attributes in visuals are:

Image credit: Colin Ware, Information Visualization, Third Edition: Perception for Design

Motion was also noted, but not shown above.

Nussbaumer Knaflic, smartly, also shows us preattentive attributes in text, which are more obvious, relatable and make sense to note here, given how often we have text in our Gantt charts:

Let’s look at a couple of applications using preattentive attributes in a plan communication. For some context, assume that we’re working to communicate a portfolio of potential drug candidates in development. Our executives want to know where the major milestones lie, but the final milestone is the most important one.

In the above example, we’ve used several preattentive attributes:

Size
Color
Enclosure (swimlane borders)
Bold text
Shape

My eyes are first pulled to the large red milestones and from there to the legend to figure out what those mean, supported by the other colors/shapes. I then begin to look at the large bold font within the swimlanes, emphasized by the swimlane borders. The actual bars that connect the milestones are thin and therefore come across as unimportant. This is a hierarchy. With some more work and feedback from others, we could probably get this hierarchical design as close to perfect as possible, but for now it works.

Here’s another example using the same plan; but in this presentation we’ve been asked to point out only the final milestones as well as anything that is “critical.” Our audience also wants to understand how firm certain estimates are.

Here we’ve pulled out all the stops, using:

Enclosure (in two ways: swimlane borders, and the blue highlighted box)
Size
Color
Italicized text
Underlined text
Bold text

While the preattentive attributes overlap a bit between the two images, they’re quite different from each other. In this second example, the first three milestone shapes in the rows become almost non-existent. They’re relegated to the background due to their color when compared to the final milestone, like the bar/line on which they sit. In the second example, we would probably pick up on a couple of those bars being black (critical), which draws us to those top two rows more easily. Last, we now have a light blue box highlighting milestones that are considered “directional” with regard to their estimates.

You have probably used preattentive attributes before. But now that you’re more conscious of them, we hope you’ll do two things: reflect on how they can improve a chart you’ve created in the past and play with different uses of the preattentive attributes in order to make your future visuals even better.

Image Source