Halliday & Matthiessen (1999: 272-3):
It is many years now since Whorf first drew attention to some of the prevailing metaphors in what he referred to as "Standard Average European" languages: such things as the way cognitive processes are typically construed in terms of concrete actions and movements in physical space: e.g. grasp, follow = 'understand', the line or direction of an argument, and so on. In a well-known paper, Reddy (1979) explored this particular domain in greater depth and showed how in English the entire semantic field of saying and sensing is permeated by what he called the "conduit metaphor", according to which meaning is "contained" in thoughts or words and may be "conveyed" along some "channel" from a speaker to a listener.