How Handwriting Boosts the Brain - WSJ
OK, This article is about how handwriting boosts the brain, but one could easily apply the same for hand drawing. There is a clear cognitive link between the hand and the brain that is activated by drawing/writing. Interfacing with a computer through a keyboard or mouse does not tap into that cognitive link. This is not to say that one should supplant the other, but it does suggest that our digital visual communication may be enhanced by better spatial understanding gained through hand drawing.