What Writing Does

I'm listening to a psychologist, Toni Schmader, report on situational cues that affect student performance, and human performance generally. She just showed a slide that summarized a research study in which boys and girls in middle school wrote 3 types of letters to younger children: an anti-drug message, a learning is incremental message, and a learning is difficult for everyone message. The first message (control message) followed by student math tests returned a significant and stereotypical gender gap. The next two messages raised girls' scores, and put them on par with boys. The key, in other words, was the writing.

Josh Smyth, one time psychology faculty member at NDSU, has done extensive research on the role of informal writing on reducing arthritis and one other medical condition, and I think he has extended that research recently. When I saw him present, however, he said that the prompt, and the nature of the writing didn't make any difference.

Another former colleague did extensive research on the role of writing on helping students come to understand evolutionary theory.

These results intuitively make sense to us writing instructors, I suspect, but I am wondering:
--what would we get from an extensive meta-analysis of what researchers in other fields are finding about writing?
--how could that information help us reframe our classes (i.e. challenge some of the stereotypes; identify the many benefits of writing)?
--what happens to writing (and writers) when we actually focus on teaching writing / writers, because most of these research findings suggest the value of writing when it is used as an instrument for learning or therapy, rather than a skill to be taught?