These Optical Illusions Stress Us Out.

Read more about this mental torture here:
  1. In this classic shadow illusion by Edward H. Adelson, A and B are the exact same shade of gray:
  2. Here's a minimalist illustration by Wikipedia user Dodek. The gray bar across the center is actually one constant color:
  3. In this image from BrainDen, the surface colors of A and B are the same. To test it out, just use your finger to cover the middle of the drawing, where the two squares meet.
  4. In this illusion by Barton L. Anderson and Jonathan Winawer, the black and white chess pieces are the same color:
  5. If you want a dog of a different color, just set it against a different background (via BrainDen):
  6. Contrasting colors can even give you the illusion of motion, as in this trippy graphic by Paul Nasca: