There's another visual/mental exercise I discovered on my own as a kid.
For some reason starting with a blank slate, in my mind I cannot draw a spiral from the outside all the way to the center. I can cognate what will happen, but I can't watch it proceed. It never gets there. As it runs out of room there is an apparatus in my brain performing a "zooming in" of some kind (to look at it closer perhaps?) This widens the space left to spiral into and I cannot ever smack into the middle.
18 on an uncalibrated 18" screen
Uncalibrated Dell 3007WFP
I got an 8, but I blame it on my crappy PC monitor and my impatience.
I need to re-do this in my theater and see if my accusations are misdirected.
My score was 8: ( it took about 5 min )
I got a 0 so I get to lord it over the the less fortunate in the household.