An anomalous brightness differentiation.
The two adjacent regions of a homogeneous surface divided by a thin line may appear different in brightness. The phenomenon is weak, but can be obtained and systematically studied under certain experimental conditions. Data suggest that the effect is influenced by both the spatial position and the relative size of the two regions. The phenomenon is worthy of further examination because it challenges current theories of brightness perception.
D003118:Color Perception; D006801:Humans; D008029:Lighting