Here's a link going around from the Free Writing Tips website. If you follow the link and do not get a large sentence reading "Graphic storytelling teaches better than text" (ahem), do a search for a column entitled "Now You See It." The piece details work from studies at Texas Tech, East Carolina, UC Santa Barbara and others that suggests words and images together in comics form help people learn and retain knowledge.
One day enough people will catch on such that articles like this will simply be entitled "Duh: Here We Go Again." But, hey, researchers, keep those studies coming.