The theory that the mind retains an image for a split second. This accounts for the fact that when a motion picture flashes a series of progressive images, instead of the mind seeing the flashing of a series of images, it sees the illusion of motion.
Through experience in the early days of film innovation, it was determined that any rate less than 16 frames per second caused the mind to see flashing images. Today's theatrical film runs at 24 frames a second and television runs barely under 30 frames a second.
Also the name of a short story by JohnVarley?
, and the title of one of his later [anthologies]