At first, blind subjects equipped with a TVSS device experience its outputs as purely tactile. After a short time, however, many subjects cease to notice the tactile stimulations themselves and instead report having quasi-visual experiences of the objects arrayed in space in front of them. Indeed, with a significant amount of supervised training, blind subjects can learn to discriminate spatial properties such as shape, size, and location and even to perform simple “eye”-hand coordination tasks such as catching or batting a ball. A main finding of relevance in early experiments was that subjects learn to “see” by means of TVSS only when they have active control over movement of the video camera. Subjects who receive visual input passively—and therefore lack any knowledge of how (or whether) the camera is moving—experience only meaningless, tactile stimulation.