However, he did not develop an ability to either understand or speak English, although he did develop an ability to communicate with sign language. Exposure to language was not enough to promote development of the ability to speak. Since the child lacked the opportunity to interact with the sounds of language, development did not occur. The importance of active experience has been illustrated over and over again in so many different ways that we now realize that experience not only fosters biological development, it is necessary for learning how to interpret the information the biological mechanisms give us. For full perceptual development, the sensory structures must be developed to their full potential, and we must learn to interpret and understand the signals that they send.
Perceptual development depends on learning as well as on physical development.
The importance of the role learning plays in perception was clearly illustrated when doctors developed a medical procedure which allowed some people, blind since birth, to gain vision. These people had learned to function adequately without the sense of sight. When, as adults, these people underwent corrective surgery, science gained dramatic new evidence showing the relationship between perception and learning. After the first patient's operation, doctors were quite anxious to see how the patient would respond after bandages were removed from her eyes. They asked if she could see.