An issue discussed during 1960s was weather human memory system has one or two components. Some authors like Arthur Melton 8) argued that both short term memory (STM) and long-term memory (LTM) are just two subcomponents dependent on the same system. He justified his views by proofs of activation of the LTM in STM experiments. His work was very influential, yet during the years more and more evidence of at least two separate memory systems have accumulated.
The first more influential two component memory model was introduced in 1968 by Richard Atkinson and Richard Shiffrni 9) . Their model called Multi-store model consisted of long-term and working or short-term memory model and was later improved by an additional component, the sensory memory. Sensory memory contains one register for each sense and serves as an short lasting buffer-zone before the information can enter short-term memory. Short-term memory is a temporal storage for new information before it enters long-term memory, but is also used for cognitive tasks, understanding and learning.
The thesis of two separate memory systems: the long-term memory and the short-term memory is today considered to be true. This thesis is supported by differences in:
§ capacity (small for STM and large or unlimited for LTM),
§ duration limits (items in STM decay as a function of time, which is not a characteristic of LTM),
§ retention speed (very high for STM and possibly lower for LTM),
§ time to acquire information (short for STM and longer for LTM),
§ information encoding (semantic for LTM and acoustic or visual for STM), and
§ type of memory affected by physical injuries in patients.
Another term should be clarified here: the working memory, which is often mistaken for the short-term memory. The main difference between these two is that working memory usually includes the structure and processes performed by a system in control of the short-term memory.