Final answer:
The 'central grey' phenomenon involves simultaneous contrast, where perception of an area's color or brightness is altered by its surroundings, demonstrating the active role of the brain in visual perception.
Step-by-step explanation:
The phenomenon described in the question seems to be related to visual perception and how the brain processes visual information, particularly with regard to color and brightness perception, which would fall under the field of Biology within the domain of sensation and perception studies.
The central grey illusion being described is known as simultaneous contrast. This is when the perception of the color or brightness of an area is affected by the surrounding colors or shades. For instance, a grey square may appear lighter or darker depending on the color or brightness of its surrounding area. Our perceptions can be deceived by our brain making inferences based on the overall visual input; this is not just a simple capture of an image like a camera, but a complex interpretation by our visual system trying to adapt and make the world appear consistent to us. This goes to show the active role the brain plays in constructing our perceptual world.