Psychology
When Shadows Deceive: The Brain's Hidden Light Assumptions
Quick fact
The brain assumes light comes from above, so a shadow at the bottom of an object makes it look like a bump, while a shadow at the top makes it look like a dent. When this assumption is tricked, we perceive depth or motion that isn't there.
Why this is interesting
Have you ever seen a shadow that seemed to move on its own, or a flat drawing that popped into 3D? Your brain might be making a silent bet about where the light is coming from—and losing.