PERSISTENCE OF VISION

In the early 19th century, it was discovered that, in addition to the blurring effect of movement (decomposition of shapes), the eye could also recompose shapes in motion, because of 'persistence of vision': the eye keeps the memory of a shape for a brief instant after perception, so that it can link with the next perception;  two separate shapes seen in close succession seem to flow one into another, so that two views of a moving object in successive positions are viewed as continuous motion. This was later seen as an explanation of the cinema, which is made of a film containing successive images, though now a different explanation (the Phi effect) is given.