wild.

I believe that once we are told ahead of time that we'll see them right-side-up in the original presentation our brains will make sure that's how we see them.

Rotating or otherwise changing the image will make the optical circuits need to reset.

the first time the trigger was the square plate in the lower right. Then I refreshed the image and it was the bowl in the lower left.

Amazing how they appear to shift back and forth in appearance

The light is coming from the right. Shadows are formed from the edges and separations on the plates/bowls. If any of them were upside down, there would be nothing to create the shadows as all the surfaces would be flat. I could see none of them as upside down.

Then I studied it a bit more and it flipped, and now I can't mentally reverse it. Weird, because I usually can usually switch back and forth on optical illusion like this.