Prior to the invention of language, human beings relied on hand gestures and then scratchings on cave walls or in the soil as the only ways that they could communicate. Today, people still communicate with drawings.
For example, Rollin King and Herb Keller scribbled out the basics of what became Southwest Airlines on napkins while having a libation in an establishment that provides them. Here is a photo of the original napkin indicating its initial flight routes:
That was in 1967. Years later, Dan Roam published his first book, The Back of the Napkin: Solving Problems and Selling Ideas with Pictures (2008). Here is his napkin:
I have just read and will soon review his latest book, Draw to Win: A Crash Course on How to Lead, Sell, and Innovate With Your Visual Mind, published by Portfolio/Penguin Random House on September 13, 2016.
Mullers such as I whose circumstances seldom enable them to brainstorm with others will find drawing and doodling especially valuable when attempting to clarify thoughts, sequences, relationships, etc.
To nourish that process, I highly recommend each of Dan Roam’s books as well as Sunni Brown’s The Doodle Revolution: Unlock the Power to Think Differently.