Bend reality
Checker Shadow Illusion
Compare the lightness of the two marked squares before reading the explanation.
Edward H. Adelson · Perception experiment
A way in
Open the image and compare the squares marked A and B. Make a judgment first. Return here afterward, then open the source page for the explanation.
Free still image with no sound or interaction. Look at the image before opening the source explanation. This illusion depends on sight; the explanation describes what is happening.
Afterward
Why we chose it
A checkerboard, a cylinder, a shadow: the image offers an ordinary scene with one precise question. Looking at it is easy; separating a patch from the scene around it is harder. There is no puzzle to race through and no score, just two squares and the shadow that makes them look different. Take the first impression seriously enough to remember it before looking for the explanation.
What it may shift The difference between a patch of gray and its apparent lightness.
A and B contain the same gray. Does knowing that change their appearance? What did the shadow help your visual system infer?