Memory Models

The sensory register is where stimuli from the environment enter memory. There are actually two separate components of sensory memory, those being Iconic (visual) and Echoic (auditory) memory. Both of these systems act as buffers to filter large amounts of incoming information as not to overwhelm higher cognition. Sights and sounds here decay in a matter of seconds unless they are given conscious attention.

Short-term memory refers to information that is readily available in your mind for a limited amount of time. The capacity of short-term memory was determined by George Miller to be 7±2. This capacity can be improved by breaking information down into "Chunks." For example, a usual seven digit phone number can become two chunks of three and four. Duration in short-term memory is longer than the sensory register, up to twenty seconds without rehearsal. 

Information in short-term memory is automatically transferred to long term-memory. Whether or not it can be recalled depends on factors such as attention, rehersal, and amount of time spent in short-term memory. Long-term memory is assumed to have a limitless capacity and duration. A human does not live long enough to reach the true capacity. Information in long-term memory will deteriorate over time if it is not retrieved with regularity.