Early on in his (quite good, and recommended) “Information Visualization: Perception for Design,” author Colin Ware aptly demonstrates the importance of visuals, in terms of cognition and understanding.
“Visualizations,” Ware writes, “have a small but crucial and expanding role in cognitive systems. Visual displays provide the highest bandwidth channel from the computer to the human. We acquire more information through vision than all of the other senses combined. The 20 billion or so neurons of the brain devoted to analyzing visual information provide a pattern-finding mechanism that is a fundamental component in much of our cognitive activity.”
That’s an academic way of stating a fact that many project managers have leveraged for years: Getting folks to understand complex concepts is hard, and pictures make it easier.