Checker Shadow
Look at Square A and Square B. A looks dark, B looks light. In reality, they are exactly the same shade of grey.
The Brain's Post-Processing
♟️ Shadow Compensation▼
Your brain knows how shadows work. It assumes that objects in shadow are actually lighter than they appear.
Because Square B is clearly "in a shadow", the brain unconsciously boosts its brightness to determine its "true" color (reflectance). It concludes "It must be a white square in the dark". Meanwhile, Square A is clearly "a dark square in the light". The raw photons hitting your eye are identical, but your perception of the materials is completely different.