# PERCEPTUAL RULES

_Perceptual rules_ help to clearly relay content by using an appropriate visual design.
They comprise the second part of this guide with the rule sets [EXPRESS](04-express.md), [SIMPLIFY](05-simplify.md), [CONDENSE](06-condense.md), and [CHECK](07-check.md).

The perceptual rules are based on the work of authors such as William [Playfair](https://www.amazon.com/Playfairs-Commercial-Political-Statistical-Breviary/dp/0521855543), Willard Cope [Brinton](https://www.amazon.com/Graphic-Methods-Presenting-Willard-Brinton/dp/1290860955), Gene [Zelazny](https://www.amazon.com/Say-Charts-Executives-Visual-Communication/dp/007136997X), Edward [Tufte](https://www.amazon.com/Visual-Display-Quantitative-Information/dp/1930824130), and Stephen [Few](https://www.amazon.com/Show-Me-Numbers-Designing-Enlighten-dp-0970601972/dp/0970601972/). All of these rules owe wide acceptance to their scientific, experimental, and/or practical experience basis.
