How did cataract surgery studies reveal the importance of visual experience for recognizing shapes?

Studies of individuals who have had their sight restored after being born with cataracts have provided significant insights into the role of visual experience in perceptual learning.

Upon the removal of cataracts, these newly sighted individuals are initially able to perceive changes in illumination and color, but they struggle to discriminate between simple shapes or remember the shape of an object they have just seen. Because they lack the ability to recognize shapes immediately, they must rely on laborious methods, such as counting the corners of a figure, to distinguish between shapes like a square and a triangle. This process of learning to identify and discriminate forms takes a long period of experience, often lasting several months.1

These findings suggest that while some basic visual functions may be innate, early visual experience is essential for maintaining and elaborating the ability to perform complex visual tasks, such as form identification and discrimination.1