I took this picture in a classroom at my son's high school. The teacher (social studies) said that he'd "borrowed" these sentence-diagramming techniques from his wife, an elementary school teacher.
He said that completion of writing exercises basically DOUBLED once students started doing this. "I can see what I'm trying to write" was their essential reaction according to him.
Kudos to the teacher, of course, for trying something new. I'm not completely surprised by the results, actually.
There's more going on here than visualization, if you think about it. Drawing that diagram - let's say, a flow map for sequencing - requires thinking through the flow. They're not just drawing boxes and arrows - they're deciding what 1, 2 and 3 are, and how they're related. They're also "externalizing" - getting the structure out of their head(s), into a tangible form. They don't have to keep that structure in their head as they wrestle with wording and phrasing.
I particularly appreciate the non-digital nature of this innovation.