"There should be materials in the classroom that provide opportunities for students to manipulate, build, or encounter other hands-on experiences."
"Implicit learning, which includes body and hand-on learning, is lasting, independent of age, easy to acquire, ctoss-cultural, and independent of measures of intelligence."
"Brain activity and the use of the hands are so interrelated and complicated that there is not one brain theory that explains it."
-- from: Worksheets Don't Grow Dendrites by Marcia Tate, p.44. (371.39 TaW 2003) - author has derived these rationales from various educators that are listed in her bibliography.
This one is pretty thin, I admit. But the checklist from the guide below is pretty good.