Human memory is a very complicated concept. There are many theories concerning how memory is encoded, processed, and stored. The Multi-Store Model of Human Memory is very similar to the actual storage of memory in a computer. The model has several weak points that have been identified by various researchers.
Atkinson and Shiffrin's Model
In 1968, Richard Atkinson and Richard Shiffrin developed the Multi-Store Model of Memory. Atkinson and Shiffrin proposed three types or "stores" of memory: Sensory Memory, Short Term Memory, and Long Term Memory. Sensory memory involves information received through the several senses of sight, hearing, touch, smell, and taste. Memory processed in this way remains in the sensory store no more than one to two seconds unless the individual pays attention to the information. Short term memory, also known as Working Memory, is stored for about 15 to 30 seconds while the individual transfers it to other processes. Information can be processed and moved between the different levels of memory as needed. Coding for long term memory is primarily visual or semantic, meaning humans typically store memory in the form of images or by the meaning of the information. Long term memory is more or less permanent memory that has no known capacity limit.
Many researchers feel the Multi-Store Model is too simplistic. Short and long term memories are far more complicated than this model suggests. Short term memory is composed of various components, such as visuo-spatial and central executive. Different types of long term memory have also been identified: general knowledge or semantic memory, memory of events or episodic memory, and knowledge of skills or procedural memory.
Atkinson and Shiffrin emphasised the importance of rehearsal to long term memory. While practice is important as a means of transferring information from short term to long term memory, it is not essential for all long term memory. Craig and Tulving proposed that the depth of processing is more important to memory than is rehearsal. More complicated processing increases the likelihood of long term memory storage.
Atkinson and Shiffrin's model has been criticised for being linear. The data shifts from sensory to short term to long term memory, with little transfer beyond that. Studies on individuals with brain damage suggests that memory is far more complicated than this linear model would suggest. It is possible to lose some but not all long term or short term memory types. This implies that there are separate brain storage areas for long and short term memory.