[zeroca]

Let’s proceed with explanations:

Reading of the part of “brief course of psychology” – perception didn’t give me the explanation of considered by us test above (the truth, it gave a lot of interesting explanations of some other phenomena). Anyway, I took first four successive phases of animations (when lagging equals to 0 degrees–I picture, and when the lagging equals to 135 degrees - II picture) and overdrew mentioned four phases for both cases. You can read on the animation the colors of each successive phase: 1.blue, 2.black, 3.red and 4.green;
(There are 16 spokes in all within each wheel).
You see clearly that in I picture (see separate sector below) the next position! of first blue spoke is marked as black; red spoke is the position of 16-th spoke (the second phase of spinning), its following - green is the position of 15-th spoke (third phase of spinning), i.e. each following position of previous spoke is close to the starting position of next spoke from the left side (in each following position).

As for the II picture, each following position of first blue spoke is disposed close to the position of the second blue spoke (each spoke from previous position takes the next position close to the former position of the next spoke) from the right side (In each following position).
I.e. eye constructed the way that “it prefers” to perceive closer next disposition - shifting to closer distance despite direction of spinning! I.e. motion is perceived by eye as sum of shiftings between closest distances of spokes’ positions.
I see that this isn’t perfect explanation, but let’s continue deeper analysis in following posts.