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'''Decay Theorytheory''' 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 away25. When we [[learn]] something new, a [[neurochemical]] “memory trace” is created. However, over time this trace slowly disintegrates. Actively [[memory rehearsal|rehearsing]] information is believed to be a major factor counteracting this temporal decline5. It is widely believed that [[neurons]] die off gradually as we age, yet some older memories can be stronger than most recent memories. Thus, Decaydecay Theorytheory 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 passes2.
The most famous classic study done in this field was the Ebbinghaus [[forgetting curve]] by [[H. Ebbinghaus]] (1885). This was one of the earliest studies done in the field of [[Psychology]]. H. Ebbinghaus used himself as subject. He invented nonsense syllables (e.g. BLF, MXW, ...), learned lists of them and then tested his memory after various time intervals. He found that forgetting was very quick just after learning (>50% in the first hour) and then leveled off. The graph of retention and forgetting is known as the Ebbinghaus curve7.
Decay alone, although it may play some role, cannot entirely explain lapses in long-term memory. A trace is formed by sensory neurons—this trace is a memory. When a person forgets, the trace is lost. The decay theory along with the [[interference theory]], [[repressed memory|motivated forgetting]], and retrieval failure theory are four suggested reasons why people forget. There are 3 kinds of Interference Theory: Proactive, Retroactive and Output.
Another theory of forgetting in short-term memory, or STM, is the Displacement Theory which suggests that new memory traces displace or erase old ones.
==Inconsistencies==
Researchers disagree about whether memories fade as a function of the mere passage of time (as in Decaydecay Theorytheory) or as a function of interfering succeeding events (as in [[Interferenceinterference Theorytheory]])1. Often, evidence tends to favour interference related decay over temporal decay 2, yet this varies depending on the specific memory system taken into account.
===Short-Term Memory===
Within the [[short-term memory]] system, evidence favours an Interferenceinterference Theorytheory 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 remember1. 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 found2. No evidence for temporal decay in verbal short-term memory has been found in recent studies of serial recall tasks2. Regarding the word-length effect in short-term memory, which states that longer word lists are harder to recall than short word lists, researchers argue that interference plays a larger role due to articulation duration being confounded with other word characteristics3.
===Working Memory===
Both theories are equally argued in [[working memory]]. One situation in which this shows considerable debate is within the [[memory span|complex-span task]] of working memory, whereas a complex task is alternated with the encoding of to-be-remembered items1. It is either argued that the amount of time taken to perform this task or the amount of interference this task involves cause decay1. A [[working memory#Time-based resource sharing model|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 information4. 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 memeory4memory4. As processing and maintenance are both crucial components of working memory, both of these processes need to be taken into account when determining which [[forgetting#Theories of forgetting|theory of forgetting]] is most valid. Research also suggests that information or an event’s [[salience (neuroscience)|salience]], or importance, may play a key role6. Working memory may decay in proportion to information or an event’s salience6. 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 explainations2. However, a close look at the literature regarding Decaydecay Theorytheory 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 [[repressed memory|motivated forgetting]] and retrieval failure theory.
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