Editing Working memory (section)

=== Experimental studies of working-memory capacity ===
There are several hypotheses about the nature of the capacity limit. One is that a limited pool of cognitive resources is needed to keep representations active and thereby available for processing, and for carrying out processes.<ref name=":0">{{cite journal | vauthors = Just MA, Carpenter PA | title = A capacity theory of comprehension: individual differences in working memory | journal = Psychological Review | volume = 99 | issue = 1 | pages = 122–149 | date = January 1992 | pmid = 1546114 | doi = 10.1037/0033-295X.99.1.122 | s2cid = 2241367 }}</ref> Another hypothesis is that memory traces in working memory decay within a few seconds, unless refreshed through rehearsal, and because the speed of rehearsal is limited, we can maintain only a limited amount of information.<ref>{{cite journal | vauthors = Towse JN, Hitch GJ, Hutton U | title = On the interpretation of working memory span in adults | journal = Memory & Cognition | volume = 28 | issue = 3 | pages = 341–348 | date = April 2000 | pmid = 10881551 | doi = 10.3758/BF03198549 | doi-access = free }}</ref> Yet another idea is that representations held in working memory interfere with each other.<ref>{{cite journal | vauthors = Waugh NC, Norman DA | title = PRIMARY MEMORY | journal = Psychological Review | volume = 72 | issue = 2 | pages = 89–104 | date = March 1965 | pmid = 14282677 | doi = 10.1037/h0021797 }}</ref>

====Decay theories====

The assumption that the contents of short-term or working memory [[decay theory|decay]] over time, unless decay is prevented by rehearsal, goes back to the early days of experimental research on short-term memory.<ref>{{Cite journal| vauthors = Brown J |year=1958|title=Some tests of the decay theory of immediate memory|journal=Quarterly Journal of Experimental Psychology|volume=10|pages=12–21|doi=10.1080/17470215808416249|s2cid=144071312}}</ref><ref>{{cite journal | vauthors = Peterson LR, Peterson MJ | title = Short-term retention of individual verbal items | journal = Journal of Experimental Psychology | volume = 58 | issue = 3 | pages = 193–198 | date = September 1959 | pmid = 14432252 | doi = 10.1037/h0049234 }}</ref> It is also an important assumption in the multi-component theory of working memory.<ref>{{Cite book|title=Working memory| vauthors = Baddeley AD |publisher=Clarendon | volume = 11 |year=1986|location=Oxford | isbn = 978-0-19-852116-7 }}</ref> The most elaborate decay-based theory of working memory to date is the "time-based resource sharing model".<ref>{{cite journal | vauthors = Barrouillet P, Bernardin S, Camos V | title = Time constraints and resource sharing in adults' working memory spans | journal = Journal of Experimental Psychology. General | volume = 133 | issue = 1 | pages = 83–100 | date = March 2004 | pmid = 14979753 | doi = 10.1037/0096-3445.133.1.83 | s2cid = 604840 }}</ref> This theory assumes that representations in working memory decay unless they are refreshed. Refreshing them requires an attentional mechanism that is also needed for any concurrent processing task. When there are small time intervals in which the processing task does not require attention, this time can be used to refresh memory traces. The theory therefore predicts that the amount of forgetting depends on the temporal density (rate and duration) of attentional demands of the processing task—this density is called ''[[cognitive load]]''. The cognitive load depends on two variables, the rate at which the processing task requires individual steps to be carried out, and the duration of each step. For example, if the processing task consists of adding digits, then having to add another digit every half-second places a higher cognitive load on the system than having to add another digit every two seconds. In a series of experiments, Barrouillet and colleagues have shown that memory for lists of letters depends neither on the number of processing steps nor the total time of processing but on cognitive load.<ref>{{cite journal |last1=Barrouillet |first1=Pierre |last2=Bernardin |first2=Sophie |last3=Portrat |first3=Sophie |last4=Vergauwe |first4=Evie |last5=Camos |first5=Valérie |title=Time and cognitive load in working memory. |journal=Journal of Experimental Psychology: Learning, Memory, and Cognition |date=2007 |volume=33 |issue=3 |pages=570–585 |doi=10.1037/0278-7393.33.3.570 |pmid=17470006 |url=https://archive-ouverte.unige.ch/unige:88299 }}</ref>

====Resource theories====

Resource theories assume that the capacity of working memory is a limited resource that must be shared between all representations that need to be maintained in working memory simultaneously.<ref name="Changing concepts of working memory"/> Some resource theorists also assume that maintenance and concurrent processing share the same resource;<ref name=":0" /> this can explain why maintenance is typically impaired by a concurrent processing demand. Resource theories have been very successful in explaining data from tests of working memory for simple visual features, such as colors or orientations of bars. An ongoing debate is whether the resource is a continuous quantity that can be subdivided among any number of items in working memory, or whether it consists of a small number of discrete "slots", each of which can be assigned to one memory item, so that only a limited number of about 3 items can be maintained in working memory at all.<ref>{{cite journal | vauthors = van den Berg R, Awh E, Ma WJ | title = Factorial comparison of working memory models | journal = Psychological Review | volume = 121 | issue = 1 | pages = 124–149 | date = January 2014 | pmid = 24490791 | pmc = 4159389 | doi = 10.1037/a0035234 }}</ref>

====Interference theories====

Several forms of [[Interference theory|interference]] have been discussed by theorists. One of the oldest ideas is that new items simply replace older ones in working memory. Another form of interference is retrieval competition. For example, when the task is to remember a list of 7 words in their order, we need to start recall with the first word. While trying to retrieve the first word, the second word, which is represented in proximity, is accidentally retrieved as well, and the two compete for being recalled. Errors in serial recall tasks are often confusions of neighboring items on a memory list (so-called transpositions), showing that retrieval competition plays a role in limiting our ability to recall lists in order, and probably also in other working memory tasks. A third form of interference is the distortion of representations by superposition: When multiple representations are added on top of each other, each of them is blurred by the presence of all the others.<ref>{{cite journal |last1=Oberauer |first1=Klaus |last2=Lewandowsky |first2=Stephan |last3=Farrell |first3=Simon |last4=Jarrold |first4=Christopher |last5=Greaves |first5=Martin |title=Modeling working memory: An interference model of complex span |journal=Psychonomic Bulletin & Review |date=October 2012 |volume=19 |issue=5 |pages=779–819 |doi=10.3758/s13423-012-0272-4 |pmid=22715024 |url=https://www.zora.uzh.ch/id/eprint/63536/1/ZORA_NL_63536.pdf }}</ref> A fourth form of interference assumed by some authors is feature overwriting.<ref>{{Cite journal|doi=10.1016/j.jml.2006.08.009 |title=A formal model of capacity limits in working memory |date=November 2006 | vauthors = Oberauer K, Kliegl R |journal=Journal of Memory and Language |volume=55 |issue=4 |pages=601–26|doi-access=free }}</ref><ref>{{cite journal | vauthors = Bancroft T, Servos P | title = Distractor frequency influences performance in vibrotactile working memory | journal = Experimental Brain Research | volume = 208 | issue = 4 | pages = 529–532 | date = February 2011 | pmid = 21132280 | doi = 10.1007/s00221-010-2501-2 | s2cid = 19743442 }}</ref> The idea is that each word, digit, or other item in working memory is represented as a bundle of features, and when two items share some features, one of them steals the features from the other. As more items are held in working memory, whose features begin to overlap, the more each of them will be degraded by the loss of some features.{{citation needed|date=July 2022}}

==== Limitations ====
None of these hypotheses can explain the experimental data entirely. The resource hypothesis, for example, was meant to explain the trade-off between maintenance and processing: The more information must be maintained in working memory, the slower and more error prone concurrent processes become, and with a higher demand on concurrent processing memory suffers. This trade-off has been investigated by tasks like the reading-span task described above. It has been found that the amount of trade-off depends on the similarity of the information to be remembered and the information to be processed. For example, remembering numbers while processing spatial information, or remembering spatial information while processing numbers, impair each other much less than when material of the same kind must be remembered and processed.<ref>{{Cite journal|doi=10.1016/j.jml.2006.07.009 |title=The relationship between processing and storage in working memory span: Not two sides of the same coin |date=February 2007 | vauthors = Maehara Y, Saito S |journal=Journal of Memory and Language |volume=56 |issue=2 |pages=212–228}}</ref> Also, remembering words and processing digits, or remembering digits and processing words, is easier than remembering and processing materials of the same category.<ref>{{Cite journal|doi=10.1076/anec.6.2.99.784 |title=Selection from Working Memory: on the Relationship between Processing and Storage Components |date=June 1999 | vauthors = Li KZ |journal=Aging, Neuropsychology, and Cognition |volume=6 |issue=2 |pages=99–116}}</ref> These findings are also difficult to explain for the decay hypothesis, because decay of memory representations should depend only on how long the processing task delays rehearsal or recall, not on the content of the processing task. A further problem for the decay hypothesis comes from experiments in which the recall of a list of letters was delayed, either by instructing participants to recall at a slower pace, or by instructing them to say an irrelevant word once or three times in between recall of each letter. Delaying recall had virtually no effect on recall accuracy.<ref>{{cite journal |last1=Lewandowsky |first1=Stephan |last2=Duncan |first2=Matthew |last3=Brown |first3=Gordon D. A. |title=Time does not cause forgetting in short-term serial recall |journal=Psychonomic Bulletin & Review |date=October 2004 |volume=11 |issue=5 |pages=771–790 |doi=10.3758/bf03196705 |pmid=15732687 }}</ref><ref>{{cite journal |last1=Oberauer |first1=Klaus |last2=Lewandowsky |first2=Stephan |title=Forgetting in immediate serial recall: Decay, temporal distinctiveness, or interference? |journal=Psychological Review |date=2008 |volume=115 |issue=3 |pages=544–576 |doi=10.1037/0033-295X.115.3.544 |pmid=18729591 |url=https://api.research-repository.uwa.edu.au/ws/files/1546099/11204_PID11204.pdf }}</ref> The [[interference theory]] seems to fare best with explaining why the similarity between memory contents and the contents of concurrent processing tasks affects how much they impair each other. More similar materials are more likely to be confused, leading to retrieval competition.