Data visualizations are effective ways for inputting information into a human’s brain, and some even state that visualizations are what makes our world real.
But even when the people who created the visualization are being honest, we can’t always trust what our eyes are showing us. We’ve evolved our visual perceptual system over millions of years (some other animals see optical illusions too) and it is extremely effective at what it does, but it still has some quirks.
In a data visualization context, illusions are dangerous because they can make us see things that aren’t really there in the data. Good practice helps us to avoid these optical illusions, but occasionally they can still sneak in through design choices, or just quirks in the way data lines up.
There are two main types of optical illusions: Physiological and Cognitive. When designing data visualizations, it can be useful to be aware of these illusions and keep an eye out for them...