Editing Short-term memory (section)

== Stores ==
The idea of separate memories for short-term and long-term storage originated in the 19th century.<ref>Norris D. (2017). Short-term memory and long-term memory are still different. Psychological bulletin, 143(9), 992–1009. https://doi.org/10.1037/bul0000108</ref> A model of memory developed in the 1960s assumed that all memories are formed in one store and transfer to other stores after a small period of time. This model is referred to as the "modal model", most famously detailed by [[Richard Shiffrin|Shiffrin]].<ref>Atkinson and Shiffrin, 1968</ref> The model states that memory is first stored in sensory memory, which has a large capacity but can only maintain information for milliseconds.<ref>{{cite journal |last1=Öğmen |first1=Haluk |last2=Herzog |first2=Michael H. |title=A New Conceptualization of Human Visual Sensory-Memory |journal=Frontiers in Psychology |date=9 June 2016 |volume=7 |page=830 |doi=10.3389/fpsyg.2016.00830 |pmc=4899472 |pmid=27375519 |doi-access=free }}</ref> A representation of that rapidly decaying memory is moved to short-term memory. Short-term memory does not have a large capacity like sensory memory, but holds information for seconds or minutes. The final storage is long-term memory, which has a very large capacity and is capable of holding information possibly for a lifetime.

The exact mechanisms by which this transfer takes place, whether all or only some memories are retained permanently, and even to have the existence of a genuine distinction between stores, remain controversial.

===Evidence===
====Anterograde amnesia====
One form of evidence supporting the existence of a short-term store comes from [[anterograde amnesia]], which is when individuals cannot learn new long-term facts and episodes. Despite these challenges, patients with this form of [[amnesia]] have an intact ability to retain small amounts of information over short time scales (up to 30 seconds) but have little ability to form longer-term memories (illustrated by [[HM (patient)|patient HM]]). This suggests that short-term store is spared from damage and diseases.<ref>{{Cite journal |last1=Smith |first1=Christine N. |last2=Frascino |first2=Jennifer C. |last3=Hopkins |first3=Ramona O. |last4=Squire |first4=Larry R. |date=2013 |title=The nature of anterograde and retrograde memory impairment after damage to the medial temporal lobe |journal=Neuropsychologia |language=en |volume=51 |issue=13 |pages=2709–2714 |doi=10.1016/j.neuropsychologia.2013.09.015 |pmc=3837701 |pmid=24041667}}</ref>

====Distraction tasks====
Other evidence comes from experimental studies showing that some manipulations such as distractions can impair the recall memory for the last 3 to 5 words most recently learned from a list of words (it is presumed that they are held in short-term memory). However, recall for words from earlier in the list (it is presumed, stored in long-term memory) are unaffected. Other manipulations (e.g., [[Semantics|semantic]] similarity of the words) affect only memory for earlier list words,<ref>{{Cite journal |last1=Davelaar |first1=E. J. |last2=Goshen-Gottstein |first2=Y. |last3=Haarmann |first3=H. J. |last4=Usher |first4=M. |last5=Usher |first5=M |year=2005 |title=The demise of short-term memory revisited: empirical and computational investigation of recency effects |journal=Psychological Review |volume=112 |issue=1 |pages=3–42 |doi=10.1037/0033-295X.112.1.3 |pmid=15631586}}</ref> but do not affect memory for the most recent few words. These results show that different factors such as distraction affect short-term recall (disruption of rehearsal) and long-term recall (semantic similarity). Together, these findings show that long-term memory and short-term memory can vary independently of each other.

===Models===
====Unitary model====
Not all researchers agree that short- and long-term memory are separate systems. The alternative Unitary Model proposes that short-term memory consists of temporary activations of long term representations (that there is one memory that behaves variously over all time scales, from milliseconds to years).<ref>{{Citation |last=Cowan |first=Nelson |title=Essence of Memory |date=2008 |volume=169 |pages=323–338 |series=Progress in Brain Research |chapter=Chapter 20 What are the differences between long-term, short-term, and working memory? |publisher=Elsevier |doi=10.1016/s0079-6123(07)00020-9 |isbn=978-0-444-53164-3 |pmc=2657600 |pmid=18394484}}</ref><ref>{{cite journal |last1=Brown |first1=G. D. A. |last2=Neath |first2=I. |last3=Chater |first3=N. |year=2007 |title=A ratio model of scale-invariant memory and identification |journal=Psychological Review |volume=114 |issue=3 |pages=539–576 |citeseerx=10.1.1.530.3006 |doi=10.1037/0033-295X.114.3.539 |pmid=17638496}}</ref> It has been difficult to identify a sharp boundary between short-term and long-term memory. For instance, Tarnow reported that the recall probability vs. latency curve is a straight line from 6 to 600 seconds, with the probability of failure to recall only saturating after 600 seconds.<ref name="Tarnow2">{{cite journal |last1=Tarnow |first1=Eugen |title=Response probability and latency: a straight line, an operational definition of meaning and the structure of short term memory |journal=Cognitive Neurodynamics |date=15 September 2008 |volume=2 |issue=4 |pages=347–353 |doi=10.1007/s11571-008-9056-y |pmid=19003463 |pmc=2585621 |url=https://web-archive.southampton.ac.uk/cogprints.org/6209/ }}</ref> If two different stores were operating in this time domain, it is reasonable to expect a discontinuity in this curve. Other research has shown that the detailed pattern of recall errors looks remarkably similar to recall of a list immediately after learning (it is presumed, from short-term memory) and recall after 24 hours (necessarily from long-term memory).<ref>{{cite journal |last1=Nairne |first1=J. S. |last2=Dutta |first2=A. |year=1992 |title=Spatial and temporal uncertainty in long-term memory |journal=Journal of Memory and Language |volume=31 |issue=3 |pages=396–407 |doi=10.1016/0749-596x(92)90020-x}}</ref>

Further evidence for a unified store comes from experiments involving continual distractor tasks. In 1974, Bjork and Whitten presented subjects with word pairs to remember; before and after each word pair, subjects performed a simple multiplication task for 12 seconds. After the final word-pair, subjects performed the multiplication distractor task for 20 seconds. They reported that the recency effect (the increased probability of recall of the last items studied) and the primacy effect (the increased probability of recall of the first few items) was sustained. These results are incompatible with a separate short-term memory as the distractor items should have displaced some of the word-pairs in the buffer, thereby weakening the associated strength of the items in long-term memory.<ref>{{cite journal |last1=Bjork |first1=R.A. |last2=Whitten |first2=W.B. |year=1974 |title=Recency-sensitive retrieval processes in long-term free recall |journal=Cognitive Psychology |volume=6 |issue=2 |pages=173–189 |doi=10.1016/0010-0285(74)90009-7 |hdl-access=free |hdl=2027.42/22374 }}</ref>

[[Ovid Tzeng|Tzeng]] (1973) reported an instance where the recency effect in [[free recall]] did not seem to result from a short-term memory store. Subjects were presented with four study-test periods of 10 word lists, with a continual distractor task (20-second period of counting-backward). At the end of each list, participants had to free-recall as many words as possible. After recall of the fourth list, participants were asked to recall items from all four lists. Both the initial and final recall showed a recency effect. These results violated the predictions of a short-term memory model, where no recency effect would be expected.<ref>{{cite journal |last1=Tzeng |first1=O.J.L. |year=1973 |title=Positive recency in delayed free recall |journal=Journal of Verbal Learning and Verbal Behavior |volume=12 |issue=4 |pages=436–439 |doi=10.1016/s0022-5371(73)80023-4}}</ref>

Koppenaal and Glanzer (1990) attempted to explain these phenomena as a result of the subjects' adaptation to the distractor task, which allowed them to preserve at least some short-term memory capabilities. In their experiment the long-term recency effect disappeared when the distractor after the last item differed from the distractors that preceded and followed the other items (e.g., arithmetic distractor task and word reading distractor task). Thapar and Greene challenged this theory. In one of their experiments, participants were given a different distractor task after every study item. According to Koppenaal and Glanzer's theory, no recency effect would be expected as subjects would not have had time to adapt to the distractor; yet such a recency effect remained in place in the experiment.<ref>{{cite journal |last1=Koppenaal |first1=L |last2=Glanzer |first2=M. |year=1990 |title=An examination of the continuous distractor task and the long-term recency effect |journal=Memory & Cognition |volume=18 |issue=2 |pages=183–195 |doi=10.3758/bf03197094 |pmid=2319960 |doi-access=free}}</ref>

====Another explanation====
One proposed explanation for recency in a continual distractor condition, and its disappearance in an end-only distractor task is the influence of contextual and distinctive processes.<ref name="Neath2">{{cite journal |last1=Neath |first1=I. |year=1993a |title=Contextual and distinctive processes and the serial position function |journal=Journal of Memory and Language |volume=32 |issue=6 |pages=820–840 |doi=10.1006/jmla.1993.1041|doi-access=free }}</ref> According to this model, recency is a result of the similarity of the final items' processing context to the processing context of the other items and the distinctive position of the final items versus intermediate items. In the end distractor task, the processing context of the final items is no longer similar to that of the other list items. At the same time, retrieval cues for these items are no longer as effective as without the distractor. Therefore, recency recedes or vanishes. However, when distractor tasks are placed before and after each item, recency returns, because all the list items have similar processing context.<ref name="Neath2" />