How presentation graphs communicate

Graphs can show up simple qualitative patterns well, but not numbers or quantities. It is argued that to convey a message, a graph has to have an explicit storyline. To be remembered, that storyline has also to be verbalized. These two requirements are seldom discussed in the literature, let alone widely practiced. It is emphasized that a graph can convey a simple qualitative relationship supremely well: "it's a curve, not a straight line". But graphics seldom convey detailed quantities or numbers in a memorable way, if at all. It is also noted briefly how presenters' familiarity with their own material often makes them grossly overestimate what anyone new to it (i.e. the typical audience) can get out of their charts.