The "shrinking" circle: I did as asked and clicked the image to see the animation. I saw no shrinking. My eyes did fatigue and I saw the border between the red and green become a blurred gradient.
You have to not blink too much or it resets the effect. After about a minute, the intense blue shows up around the red. And I say that as a man who has yet to see anything in a Magic Eye poster after a half century of what some would call life.
I also lack stereopsis- those posters are always just noise to me. I always wonder whether some of these visual tests only work on those with normal stereo perception.
What should I have experienced?