One of the most dramatic, although rare, human experiences is the acquisition of sight by blind individuals. A common misconception has been that light stimulation itself is sufficient to generate functionally meaningful vision. Historical cases of people regaining their sight after many years of blindness often ended in tragedy, with the great expectation that they would be able to see being crushed by the confusion of light that made no sense to the visually inexperienced brain. As a result, people gave up the attempt, reverted to a life of blindness and sank into deep depression.
How do we learn to see? This is an ancient debate that has intrigued scientists and philosophers for centuries. In An Essay Concerning Human Understanding (1690), John Locke famously posed the question of whether a man who was born blind and regained sight as an adult could distinguish between a cube and a sphere without touching them. It is now recognized that vision is not a spontaneous process that is 'hardwired' in the visual system — it also requires knowledge, experience and other complex sensory inputs.
