View source for Size Constancy

'''Size constancy''' is the perceptual phenomenon whereby objects are perceived as maintaining their true physical size despite changes in the size of their retinal image caused by changes in viewing distance. A person walking away does not appear to shrink; the visual system compensates for distance using binocular disparity, motion parallax, texture gradients, and prior knowledge about familiar objects. Size constancy is not a simple geometric correction but an inference about the most probable world structure consistent with the sensory data. It fails predictably in environments that violate the statistical assumptions on which the visual system's priors are calibrated — which is why [[Muller-Lyer Illusion|certain illusions]] are not errors but the correct operation of a system tuned to a different environment. The phenomenon raises a deeper question: if size is not given by the retina but reconstructed by the brain, then what other properties we take as immediately perceived are actually inferred?

[[Category:Consciousness]]
[[Category:Neuroscience]]
[[Category:Perception]]