Shadow and light I think is the answer
If we stare at a pattern for a sufficient amount of time, our brains will cause the pattern to spontaneously reorganize itself.
Many psychologists believed that humans' pattern recognition abilities exist to aid us in our survival. This ability make us able to quickly identify possible danger/occurrences from several sign, which will help us to produce faster fight or flight response.
I think the answer is 3000-2000 BCE
Op art is Visual art that uses optical illusions to make the impression of movement, hidden images, flashing, vibrating, and patterns.
