Well, I admit that I havent delved into the full research, but really I am struggling to understand how a number moving around a blank screen is clearer than the modern generation of synthetic vision panels that are being introduced. Denti posted a very good example, and many others are out there.
I believe putting an accurate picture of the outside world, relative to you, whatever your present attitude, is the best method. And these new synthetic vision displays are amazing. I fly the PlaneView on the G550 and it is like the Falcon Easy displays as well, you really have a good SA.