In 1827 John Ayrton Paris created the thaumatrope (from Greek ‘wonder’ combined with ‘motion’), a round disc threaded on a string with one picture on one side and another on the reverse; when the disc spun, the images merged. This was the first device to tune into the ‘critical fusion frequency’ of human visual perception, the speed at which the brain no longer grasps individual images but superimposes one on the other. Andy Gomez, Slade Graduate Research 2o14
Image source: http://praxinoscope.free.fr/