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==Summary==
[[File:Multistore model.png|thumb|327px|right|'''Multi-store model''': Atkinson and Shiffrin's (1968) original model of memory, consisting of the sensory register, short-term store, and long-term store.]]
The model of memories is an explanation of how memory processes work. The three-part, multi-store model was first described by Atkinson and Shiffrin in 1968,<ref name=AtkinsonShiffrin1968 /> though the vacvague idea of distinct memory stores was by no means a new idea at the time. [[William James]] described a distinction between primary and secondary memory in 1890, where primary memory consisted of thoughts held for a short time in consciousness and secondary memory consisted of a permanent, unconscious store.<ref name=James1890 />But at the time the [[Occam's razor|parsimony]] of separate memory stores was a contested notion. A summary of the evidence given for the distinction between long-term and short-term stores is given [[#Evidence for distinct stores|below]]. Additionally, Atkinson and Shiffrin included a sensory register alongside the previously theorized primary and secondary memory, as well as a variety of control processes which regulate the transfer of memory.
Following its first publication, multiple extensions of the model have been put forth such as a precategorical acoustic store,<ref name=CrowderMorton1969 /> the search of associative memory model,<ref name=RaaijmakersShiffrin1981 /><ref name=ShiffrinRaaijmakers1992/> the perturbation model,<ref name=Estes1972 /><ref name=Lee1992 /> and permastore.<ref name=Bahrick1984 /> Additionally, alternative frameworks have been proposed, such as procedural reinstatement,<ref name=HealyEtAl1992 /> a distinctiveness model,<ref name=NeathCrowder1990 /> and [[Baddeley's model of working memory|Baddeley and Hitch's model of working memory]],<ref name=BaddeleyHitch1974 /> among others.
==Sensory register==
{{Main|Sensory memory}}
When an environmental stimulus is detected by the senses, it is briefly available in what Atkinson and Shiffrin called the ''sensory registers'' (also ''sensory buffers'' or ''[[sensory memory]]''). Though this store is generally referred to as "the sensory register" or "sensory memory", it is actually composed of multiple registers, one for each sense. The sensory registers do not process the information carried by the stimulus, but rather detect and hold information for milliseconds to seconds to be used in short-term memory.<ref>{{Cite book |last=Goldstein |first=E. Bruce |url=https://www.worldcat.org/oclc/1055681278 |title=Cognitive psychology : connecting mind, research, and everyday experience |date=2019 |isbn=978-1-337-40827-1 |edition=5E |___location=Boston, MA, USA |oclc=1055681278}}</ref> For this reason Atkinson and Shiffrin also called the registers "buffers", as they prevent immense amounts of information from overwhelming higher-level cognitive processes. Information is only transferred to the short-term memory when attention is given to it, otherwise it decays rapidly and is forgotten.<ref name=AtkinsonShiffrin1968 />
While it is generally agreed that there is a sensory register for each sense, most of the research in the area has focused on the visual and auditory systems.
===Capacity===
There is a limit to the amount of information that can be held in the short-term store: 75 ±- 29 [[Chunking (psychology)|chunks]].<ref name=Miller1956 /> These chunks, which were noted by Miller in his seminal paper ''The Magical Number Seven, Plus or Minus Two'', are defined as independent items of information. It is important to note that some chunks are perceived as one unit though they could be broken down into multiple items, for example "1066" can be either the series of four digits "1, 0, 6, 6" or the semantically grouped item "1066" which is the year the [[Battle of Hastings]] was fought. [[Chunking (psychology)|Chunking]] allows for large amounts of information to be held in memory: 149283141066 is twelve individual items, well outside the limit of the short-term store, but it can be grouped semantically into the 4 chunks "[[Christopher Columbus|Columbus]][1492] ate[8] pie[314→3.14→[[pi|{{pi}}]]] at the [[Battle of Hastings]][1066]". Because short-term memory is limited in capacity, it severely limits the amount of information that can be attended to at any one time.
==Long-term store==
===Transfer from STS===
Information is postulated to enter the long-term store from the short-term store more or less automatically. According Asto Atkinson and Shiffrin model it, transfer from the short-term store to the long-term store is occurring for as long as the information is being attended to in the short-term store. In this way, varying amounts of attention result in varying amounts of time in short-term memory. Ostensibly, the longer an item is held in short-term memory, the stronger its memory trace will be in long-term memory. Atkinson and Shiffrin cite evidence for this transfer mechanism in studies by Hebb (1961)<ref name=Hebb1961 /> and Melton (1963)<ref name=Melton1963 /> which show that repeated rote repetition enhances long-term memory. One may also think to the original Ebbinghaus memory experiments showing that forgetting increases for items which are studied fewer times.<ref name=Ebbinghaus /> Finally, the authors note that there are stronger encoding processes than simple rote rehearsal, namely relating the new information to information which has already made its way into the long-term store.<ref name=AtkinsonShiffrin1968 />
===Capacity and duration===
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