We all know that the acts of comprehending and producing language are performed within the constraints of our information processing system. This system consists of three structural components! sensory memory, working memory and permanent memory! a along with a set of control processes that govern the flow of information within the system (see Gagne, 1977). In this system the environmental stimuli can only be encoded, stored and retrieved through a set of psychological processes. Thus, the central part of the system is memory.

1. 1 Components of the memory system Although the rise of information processing accounts of cognition cannot be ascribed uniquely to the development of the computer, the early cognitive psychologists' descriptions of human thinking use distinctly computer like terms. Like computers, people were supposed to take information from the environment into "buffers," to "process" it before "storing it in memory." Information-processing models describe the nature and function of putative "units" within the human perceptual and cognitive systems, and how they interact. They trace their origins to Atkinson and Shiffrin's (1968) model of memory, which was the first to suggest that memory consisted of a sensory register, a long-term and a short-term store. According to Atkinson and Shiffrin's account, information is registered by the senses and then placed into a short-term storage area. Here, unless it is worked with in a "rehearsal buffer," it decays after about 15 seconds.

If information in the short-term store is rehearsed to any significant extent, it stands a chance of being placed into the long-term store, where it remains more or less permanently. 1. 1. 1 Sensory buffers The sensory buffers or sensory stores take in the variety of colors, tones, tastes, and smells that we experience each and retain them, for a brief time, in a raw, un analyzed form (Carroll, 2000).