Don't praise or blame kids' work -- how did this get started?

I came across (never mind how) a workbook for presenting Biblical stories to children. the workbook came out around ten years ago. it stated in no uncertain terms that you should only make statements along the lines of, “you use a lot of blue” or “you like to draw big pictures”, rather than saying you liked it. I know what as a kid, I felt very sensitive to condescension and to deprive children of praise seems intuitively wrong, if not cruel.

so who came up with this particular bit of social engineering and when? and for what stated rationale?