RoseTracker| In a remarkable study using functional magnetic resonance imaging (fMRI), responses to the Ebbinghaus illusion test in which people answer which small circle is larger and also the Ponzo illusion test, are directly related to the size of our visual cortex. We already know that the size of the visual cortex differes by up to three times from one individual to the next.
The smaller the area of the visual cortex, the more pronounced the visual illusion. The degree to which our brain ‘tricks you’ is directly related to how much ‘real estate’ your brain has available for visual processing. via Science Daily