The term beta movement is used for the optical illusion of apparent motion in which the very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one figure moving.
I’m still very confused after reading the article. Is the effect that we can kinda see a “snake” moving in this animation? Because that seems different from the explanation (very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one figure moving); in the snake example, at least I don’t see any “projected figure” moving, instead the projected figures form a shape, and that shape “seems to be moving” (and even then not really, I am consciously interpreting this as movement rather than being convinced that it is). I tried looking for another visual example online but the web is so broken that I couldn’t find anything but videos of AI voices reading the same wiki article over a static frame of this same animation.
The Zipper on buildings is a clearer example, especially the original which was made of incandescent bulbs. An image is displayed, then it is displayed 1X space to the left, a new image replaces it.
But that’s just how any digital video works, no? And on the Wiki it seems to suggest that beta movement is somehow different:
The illusion of motion caused by animation and film is sometimes believed to rely on beta movement, as an alternative to the older explanation known as persistence of vision. However, the human visual system can’t distinguish between the short-range apparent motion of film and real motion, while the long-range apparent motion of beta movement is recognised as different and processed in a different way