Figure 1. Find your blind spots
Figure 1. Fixate your eyes on the black square with your
face about 20 cm (8 inches) from the screen. When you close your
right eye, the left spot should disappear, while when you close your left
eye, the right spot will disappear. You may have to move your head
forward and back a bit to find your blind spot. Note that the fill-in
area is yellow - since the surround of the blind spot is yellow.
That is the visual system's best guess as to what should be there!