Just stumbled upon this paper:

Drawing rules: the importance of the whole brain for learning realistic drawing - Scott M. Clare

THIS is what I keep saying about the whole "right side of the brain" thesis (and this guy seems to have tested it in 83 - need to get this paper, though the result is predictable). Edwards herself ends up using "left-brain" techniques when she wants to correct the usual "shrinking skull visual fallacy". Why would she need that?

And why would one ever want to leave half a brain unemployed?