Persistence of vision

"Persistence of vision" is where the retina holds a image a split second after the image was seen this links to animation because the eye creates an illusion of motion when we see images in closely timed sequence to one another. The eye cant see the fractional gaps in the motion thus making it seamless to the eye.

For example this horse is a series of still images but to the eye it is a seamless motion of movement. This is the principles for all animation and how the eye sees still images. Animation not done to a high standard this where the eye will see jerks in the movement not making it seamless like the one above.