Visual illusions or optical illusions arise from disconnect between perception and reality often brought about by a misinterpretation of the sensory inflow. While perception functions in a constructive manner, contexts, expectations, and previous experiences are all considered in the interpretation of stimuli.
A perfect example is the Müller-Lyer illusion, where marks with arrow fins at both ends of a line lead a viewer to wrongly assess the distance between the ends of both lines. It is apparent that visual illusions are critical to the understanding of perception and the brain’s tendency to employ strategies and shortcuts in a complicated world. Neuroscience has proven that an illusion activates a network of brain regions including the visual cortex and regions devoted to higher order processing.
In addition, they are helpful in studying perceptual disparity in psychological disorders, including schizophrenia or autism. In general, illusions underscore the point that perception is not merely an act of passive reception of information, but deeply an active mental construction of it.