The phi phenomenon is an illusion where one perceives a continuous motion in separate objects displayed rapidly in succession. The phenomenom was identified by Max Wertheimer in his 1912 paper ‘Experimental Studies of the Perception of Motion’. Films and animation are examples of the phi phenomenon.

Source:

Wertheimer, Max (1912), “Experimentelle Studien uber das Sehen von Bewegung” (Experimental Studies of the Perception of Motion), Zeitschrift fur Psychologie 61, 1912: 161-265.