[RoseyT]

The 3D ones? I love those. I can make the image in them pop out almost instantly.
http://www.magiceye.com/3dfun/stwkdisp.shtml

I finally got the cat to switch directions by gazing just to the left of it.

[Sunshine Sister]

Yes, the 3D posters. I could see the picture a lot quicker if the ink was darker. I had a real hard time seeing the "picture" if it was red.

I just had to look at the ones in this post for about 30 to 60 seconds before they started turning around. It's kind of weird how that works.