Humans have a limited set of senses and motor skills. The current media stimulate and reinforce only some of them. For example, the internet enhanced the visual senses over the aural. A successful new medium will "retrieve" and enhance a sense or skill that the current media do not stimulate. Since the number of senses and skills is limited, an older, outdated medium had probably addressed this sense or skill. 'What recurrence or retrieval of earlier actions and services is brought into play simultaneously by the new form?' (McLuhan)