Decay theory

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The Decay theory is a theory that proposes that memory fades due to the mere passage of time. Information is therefore less available for later retrieval as time passes and memory, as well as memory strength, wears away. [1] When an individual learns something new, a neurochemical "memory trace" is created. However, over time this trace slowly disintegrates. Actively rehearsing information is believed to be a major factor counteracting this temporal decline. [2] It is widely believed that neurons die off gradually as we age, yet some older memories can be stronger than most recent memories. Thus, decay theory mostly affects the short-term memory system, meaning that older memories (in long-term memory) are often more resistant to shocks or physical attacks on the brain. It is also thought that the passage of time alone cannot cause forgetting, and that decay theory must also take into account some processes that occur as more time passes. [1]

Contents

History

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The term "decay theory" was first coined by Edward Thorndike in his book The Psychology of Learning in 1914. [3] This simply states that if a person does not access and use the memory representation they have formed the memory trace will fade or decay over time. This theory was based on the early memory work by Hermann Ebbinghaus in the late 19th century. [4] The decay theory proposed by Thorndike was heavily criticized by McGeoch and his interference theory. [5] This led to the abandoning of the decay theory, until the late 1950s when studies by John Brown and the Petersons showed evidence of time based decay by filling the retention period by counting backwards in threes from a given number. This led to what is known as the Brown–Peterson paradigm. [6] [7] The theory was again challenged, this time a paper by Keppel and Underwood who attributed the findings to proactive interference. [8] Studies in the 1970s by Reitman [9] [10] tried reviving the decay theory by accounting for certain confounds criticized by Keppel and Underwood. Roediger quickly found problems with these studies and their methods. [11] Harris made an attempt to make a case for decay theory by using tones instead of word lists and his results are congruent making a case for decay theory. [12] In addition, McKone used implicit memory tasks as opposed to explicit tasks to address the confound problems. They provided evidence for decay theory, however, the results also interacted with interference effects. [13] [14] One of the biggest criticisms of decay theory is that it cannot be explained as a mechanism and that is the direction that the research is headed.

Inconsistencies

Researchers disagree about whether memories fade as a function of the mere passage of time (as in decay theory) or as a function of interfering succeeding events (as in interference theory). [15] Evidence tends to favor interference-related decay over temporal decay, [1] yet this varies depending on the specific memory system taken into account.

Short-term memory

Within the short-term memory system, evidence favours an interference theory of forgetting, based on various researchers' manipulation of the amount of time between a participant's retention and recall stages finding little to no effect on how many items they are able to remember. [15] Looking solely at verbal short-term memory within studies that control against participants' use of rehearsal processes, a very small temporal decay effect coupled with a much larger interference decay effect can be found. [1] No evidence for temporal decay in verbal short-term memory has been found in recent studies of serial recall tasks. [1] Regarding the word-length effect in short-term memory, which states that lists of longer word are harder to recall than lists of short words, researchers argue that interference plays a larger role due to articulation duration being confounded with other word characteristics. [16]

Working memory

Both theories are equally argued in working memory. One situation in which this shows considerable debate is within the complex-span task of working memory, where a complex task is alternated with the encoding of to-be-remembered items. [15] It is either argued that the amount of time taken to perform this task or the amount of interference this task involves cause decay. [15] A time-based resource-sharing model has also been proposed, stating that temporal decay occurs once attention is switched away from whatever information is to be remembered, and occupied by processing of the information. [17] This theory gives more credit to the active rehearsal of information, as refreshing items to be remembered focuses attention back on the information to be remembered in order for it to be better processed and stored in memory. [17] As processing and maintenance are both crucial components of working memory, both of these processes need to be taken into account when determining which theory of forgetting is most valid. Research also suggests that information or an event's salience, or importance, may play a key role. [18] Working memory may decay in proportion to information or an event's salience. [18] This means that if something is more meaningful to an individual, that individual may be less likely to forget it quickly.

System interaction

These inconsistencies may be found due to the difficulty with conducting experiments that focus solely on the passage of time as a cause of decay, ruling out alternative explanations. [1] However, a close look at the literature regarding decay theory will reveal inconsistencies across several studies and researchers, making it difficult to pinpoint precisely which indeed plays the larger role within the various systems of memory. It could be argued that both temporal decay and interference play an equally important role in forgetting, along with motivated forgetting and retrieval failure theory.

Future directions

Revisions in decay theory are being made in research today. The theory is simple and intuitive, but also problematic. Decay theory has long been rejected as a mechanism of long term forgetting. [5] Now, its place in short term forgetting is being questioned. The simplicity of the theory works against it in that supporting evidence always leaves room for alternative explanations. Researchers have had much difficulty creating experiments that can pinpoint decay as a definitive mechanism of forgetting. Current studies have always been limited in their abilities to establish decay due to confounding evidence such as attention effects or the operation of interference. [1]

Hybrid theories

The future of decay theory, according to Nairne (2002), should be the development of hybrid theories that incorporate elements of the standard model while also assuming that retrieval cues play an important role in short term memory. [19] By broadening the view of this theory, it will become possible to account for the inconsistencies and problems that have been found with decay to date.

Neuronal evidence

Another direction of future research is to tie decay theory to sound neurological evidence. As most current evidence for decay leaves room for alternate explanations, studies indicating a neural basis for the idea of decay will give the theory new solid support. Jonides et al. (2008) found neural evidence for decay in tests demonstrating a general decline in activation in posterior regions over a delay period. [20] Though this decline was not found to be strongly related to performance, this evidence is a starting point in making these connections between decay and neural imaging. A model proposed to support decay with neurological evidence places importance on the firing patterns of neurons over time. [20] The neuronal firing patterns that make up the target representation fall out of synchrony over time unless they are reset. The process of resetting the firing patterns can be looked at as rehearsal, and in absence of rehearsal, forgetting occurs. This proposed model needs to be tested further to gain support, and bring firm neurological evidence to the decay theory. [20]

Related Research Articles

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Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to short-term and working memory, which persist for only about 18 to 30 seconds. LTM is commonly labelled as "explicit memory" (declarative), as well as "episodic memory," "semantic memory," "autobiographical memory," and "implicit memory".

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The interference theory is a theory regarding human memory. Interference occurs in learning. The notion is that memories encoded in long-term memory (LTM) are forgotten and cannot be retrieved into short-term memory (STM) because either memory could interfere with the other. There is an immense number of encoded memories within the storage of LTM. The challenge for memory retrieval is recalling the specific memory and working in the temporary workspace provided in STM. Retaining information regarding the relevant time of encoding memories into LTM influences interference strength. There are two types of interference effects: proactive and retroactive interference.

The Atkinson–Shiffrin model is a model of memory proposed in 1968 by Richard Atkinson and Richard Shiffrin. The model asserts that human memory has three separate components:

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  2. a short-term store, also called working memory or short-term memory, which receives and holds input from both the sensory register and the long-term store, and
  3. a long-term store, where information which has been rehearsed in the short-term store is held indefinitely.

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References

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  2. ↑ Oberauer K, Lewandowsky S (2008). "Forgetting in immediate serial recall: Decay, temporal distinctiveness, or interference?" (PDF). Psychological Review. 115 (3): 544–576. doi:10.1037/0033-295X.115.3.544. PMID   18729591.
  3. ↑ Thorndike EL (1914). The Psychology of Learning. New York: Teachers College. p. 4.
  4. ↑ Ebbinghaus H (1885–1913). Memory. A Contribution to Experimental Psychology. New York: Teachers College/Columbia Univ.
  5. 1 2 McGeoch JA (July 1932). "Forgetting and the law of disuse". Psychological Review. 39 (4): 352–370. doi:10.1037/h0069819.
  6. ↑ Brown J (February 1958). "Some tests of the decay theory of immediate memory". Quarterly Journal of Experimental Psychology. 10 (1): 12–21. doi:10.1080/17470215808416249. S2CID   144071312.
  7. ↑ Peterson LR, Peterson MJ (September 1959). "Short-term retention of individual verbal items". Journal of Experimental Psychology. 58 (3): 193–8. doi:10.1037/h0049234. PMID   14432252.
  8. ↑ Keppel G, Underwood BJ (October 1962). "Proactive inhibition in short-term retention of single items". Journal of Verbal Learning and Verbal Behavior. 1 (3): 153–61. doi:10.1016/S0022-5371(62)80023-1.
  9. ↑ Reitman JS (April 1971). "Mechanisms of forgetting in short-term memory". Cognitive Psychology. 2 (2): 185–95. doi:10.1016/0010-0285(71)90008-9. hdl: 2027.42/33676 .
  10. ↑ Reitman JS (August 1974). "Without surreptitious rehearsal, information in short-term memory decay". Journal of Verbal Learning and Verbal Behavior. 13 (4): 365–77. doi:10.1016/S0022-5371(74)80015-0. hdl: 2027.42/22300 .
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  12. ↑ Harris JD (November 1952). "Pitch discrimination". The Journal of the Acoustical Society of America. 24 (6): 750–5. Bibcode:1952ASAJ...24..750H. doi:10.1121/1.1906970.
  13. ↑ McKone E (September 1995). "Short-term implicit memory for words and nonwords". Journal of Experimental Psychology: Learning, Memory, and Cognition. 21 (5): 1108–26. doi:10.1037/0278-7393.21.5.1108.
  14. ↑ McKone E (November 1998). "The decay of short-term implicit memory: unpacking lag". Memory & Cognition. 26 (6): 1173–86. doi: 10.3758/bf03201193 . PMID   9847544. S2CID   9058460.
  15. 1 2 3 4 Lewandowsky S, Oberauer K (November 2009). "No evidence for temporal decay in working memory". Journal of Experimental Psychology: Learning, Memory, and Cognition. 35 (6): 1545–51. doi:10.1037/a0017010. PMID   19857023.
  16. ↑ Lewandowsky S, Oberauer K (October 2008). "The word-length effect provides no evidence for decay in short-term memory". Psychonomic Bulletin & Review. 15 (5): 875–88. doi: 10.3758/PBR.15.5.875 . PMID   18926980. S2CID   9604394.
  17. 1 2 Portrat S, Barrouillet P, Camos V (November 2008). "Time-related decay or interference-based forgetting in working memory?". Journal of Experimental Psychology: Learning, Memory, and Cognition. 34 (6): 1561–4. doi:10.1037/a0013356. PMID   18980415.
  18. 1 2 Buhusi CV, Meck WH (July 2006). "Interval timing with gaps and distracters: evaluation of the ambiguity, switch, and time-sharing hypotheses". Journal of Experimental Psychology: Animal Behavior Processes. 32 (3): 329–38. doi:10.1037/0097-7403.32.3.329. PMID   16834500.
  19. ↑ Nairne JS (2002). "Remembering Over the Short-Term: The Case Against the Standard Model". Annual Review of Psychology . 53 (1): 53–81. doi:10.1146/annurev.psych.53.100901.135131. PMID   11752479.
  20. 1 2 3 Jonides J, Lewis RL, Nee DE, Lustig CA, Berman MG, Moore KS (2008). "The mind and brain of short-term memory". Annual Review of Psychology. 59 (1): 193–224. doi:10.1146/annurev.psych.59.103006.093615. PMC   3971378 . PMID   17854286.
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