The Big Book of Dashboards. Shaffer Jeffrey

Our Visual Processing System Betrays Us

      We have talked about how to use preattentive attributes to craft good data visualizations. By using those attributes, we can use the power of our visual system to our advantage. Unfortunately, our visual system also can be confused easily. In this section, we look at some common pitfalls.

Our eyes can be fooled in countless different ways. Figures 1.37 and 1.38 show two optical illusions.

Figure 1.37 Is it a duck or a rabbit?

      Source: Public domain. https://commons.wikimedia.org/w/index.php?curid=667017

      In Figure 1.38, the top appears to be a well-lit gray surface and the bottom appears to be a poorly lit white surface that is in shadow. However, there is no shadow. Dr. Lotto added the gradient and shadows to the image. Our minds can't help but to see the shadow, making the top appear to be much darker than the bottom, but if you cover up the middle of the image, it becomes clear that the top and the bottom are exactly the same color.