Instructions (Plate13):

Close left eye and fix right eye on the cross. Place eyes about 12 inches (30 cm) away from the monitor (distance may vary depending on the screen resolution) and notice the dot disappears.

Plate8 Blind Spot- Exercise A

Note that the dot is replaced, not by a black region, but rather blank white space. This is because the brain simply "fills in" the most probable stimulus (in this case, a uniform white area) where there is none.

The following examples demonstrate the "filling-in" phenomenon in greater detail. Apply the same instructions as given above and notice the red markings each time are replaced by the most probable pattern that your brain is able to perceive.

Plate9 Blind Spot- Exercise B

Plate10 Blind Spot- Exercise C

(Ref. http://www.personal.kent.edu/~rmuhamma/OpticalIllusion/illusion.html ; June 5, 2012)

All the above three Blind Spot- Exercises show the deficiency of human eyes that may create various illusionistic images.