https://sculpturetech.art.blog/2025/12/21/that-mona-lisa-smile/ That fascinating smile can be dissected mathematically to show how the artist achieved this unique effect. Spoiler--it's actually two portraits and it uses remarkable technique to cause the viewer to shift back and forth.
Thanks for the link. I’ll check it out after the holidays! Margaret Livingston, a neurobiologist from Harvard, wrote a book titled Vision and Art, The Biology of Seeing, where she explains art illusions and talks about the Mona Lisa, which is also the cover. If you enjoy this topic you would love her book! https://www.amazon.com/Vision-Art-Biology-Margaret-Livingstone/dp/0810995549
Why thank you. I'll certainly have a look. I'll be surprised if this has never been observed before, but weird stuff gets overlooked sometimes!