Long-Term Memory: Retrieval and Forgetting (Information Processing Theory)

Retrieval Strategies

When a scholar is posed a query, such as, “What functions does the Vice-President of the United States execute within the Senate?”, the inquiry enters the scholar’s Working Memory (WM) and is dissected into propositions. The neurological underpinnings of this process are not entirely elucidated; however, extant evidence suggests that information instigates associated data within memory networks via a process of spreading activation to ascertain whether the query can be resolved. If resolution is attainable, the information is rendered into a sentence and conveyed verbally, or into motor patterns for transcription. Should the activated propositions fail to furnish an answer, activation propagates until the requisite answer is located. In instances where insufficient time is afforded for spreading activation, students may proffer an educated conjecture (Anderson, 1990).

A considerable portion of cognitive processing transpires automatically. We routinely recall our abode, telephone registry, Social Security number, and the appellations of intimate acquaintances. Individuals are often unaware of the totality of steps undertaken to address a query. Nevertheless, when individuals are compelled to adjudicate between several activated propositions to ascertain their suitability in addressing the question, their awareness of the process is heightened.

Given that knowledge is encoded as propositions, retrieval proceeds irrespective of whether the information to be retrieved exists in precise form within memory. Should an educator inquire whether the Vice-President would cast a ballot in the event of an initial tally of 51 in favour and 49 in opposition, scholars could retrieve the proposition that the Vice-President casts a ballot solely in the event of a deadlock. By implication, the Vice-President would abstain. Processing of this nature, involving construction, necessitates a greater duration than when a question necessitates information coded in memory in an identical form, yet scholars should furnish a correct response assuming activation of pertinent propositions within Long-Term Memory (LTM). An analogous process is implicated in rule acquisition and transfer: scholars acquire a rule (e.g., the Pythagorean theorem in mathematics) and subsequently recall and apply it to derive solutions to problems previously unencountered.

Encoding Specificity

Retrieval is contingent upon the method of encoding. According to the encoding specificity hypothesis (Brown & Craik, 2000; Thomson & Tulving, 1970), the manner in which knowledge is encoded dictates which retrieval cues will effectively activate that knowledge. From this vantage, optimal retrieval transpires when retrieval cues correspond with those present during learning (Baddeley, 1998).

Empirical evidence lends credence to encoding specificity. When individuals are presented with category names during the encoding of specific instances within those categories, their recall of these instances is enhanced if provided with the category names at recall (Matlin, 2009). A parallel advantage is observed when learning words with associates, with the provision of associate names at recall augmenting retrieval. Brown (1968) furnished scholars with a partial registry of U.S. states for review; a separate cohort received no registry. Subsequently, all scholars endeavoured to recall as many states as feasible. Scholars furnished with the registry recalled a greater proportion of states featured therein, and a diminished proportion of states omitted.

Encoding specificity extends to encompass context. In one investigation (Godden & Baddeley, 1975), scuba divers assimilated a word list either on terra firma or subaquatically. In a subsequent free recall task, participants exhibited superior recall when tested in the environment congruent with that of learning, as opposed to the alternate environment.

Encoding specificity may be explicated in terms of spreading activation across propositional networks. Cues associated with material undergoing assimilation are linked within LTM at the epoch of encoding. During recall, presentation of these cues activates pertinent sections within LTM. Absent the aforementioned cues, recall hinges upon the recollection of individual propositions. Given that the cues engender spreading activation (as opposed to individual propositions or concepts), recall is facilitated by the presentation of identical cues during both encoding and recall. Supplementary evidence intimates that retrieval is partly guided by anticipations regarding requisite information, and that individuals may distort incongruous information to align it with their preconceptions (Hirt, Erickson, & McDonald, 1993).

Retrieval of Declarative Knowledge

Although declarative knowledge is frequently processed automatically, its integration with pertinent information within LTM is not invariably assured. This is exemplified in the scenario prefacing this discourse. Information pertaining to algebraic variables and operations lacks profound significance for scholars, thus impeding its effective integration with extant information in memory. Meaningfulness, elaboration, and organisation augment the potential for declarative information to be effectively processed and retrieved. Application 'Organising Information by Networks' furnishes pedagogical exemplars.

Meaningfulness enhances retrieval. Nonmeaningful information will fail to activate information within LTM and will be forfeited unless scholars rehearse it repeatedly until it becomes ensconced in LTM, potentially through the formation of a novel propositional network. Alternatively, one may connect the sounds of novel information, devoid of meaning, to similar sounds. The appellation constitution, for instance, may be linked phonetically with other utilisations of the term stored in learners’ memories (e.g., Constitution Avenue).

Meaningful information is more likely to be retained owing to its facile connection with propositional networks. In the introductory scenario, a proposed remedy involves relating algebraic variables to tangible objects—entities comprehended by scholars—thereby imbuing algebraic notation with meaning. Meaningfulness not only fosters learning, but also conserves temporal resources. Propositions within WM necessitate processing time; Simon (1974) estimated that each novel datum necessitates 10 seconds for encoding, thereby limiting the processing capacity to six novel data per minute. Even in instances where information is meaningful, a substantial proportion of knowledge is forfeited prior to encoding. While not every incoming datum is critical, and a degree of attrition is often inconsequential, scholars typically retain only a modicum of information, even under optimal circumstances.

Elaboration entails augmenting information undergoing assimilation with exemplars, particulars, inferences, or any mechanism that serves to bridge novel and established information. A learner might elaborate upon the role of the Vice-President within the Senate by meticulously scrutinising the roll call, and, in the event of a deadlock, the Vice-President casting a ballot.

Elaboration facilitates learning insofar as it constitutes a form of rehearsal: By sustaining information's activity within WM, elaboration augments the likelihood of its permanent storage within LTM. This facilitates retrieval, concomitant with the establishment of linkages between established and novel information. Scholars who elaborate upon the role of the Vice-President within the Senate connect this novel information with their extant comprehension of the Senate and the Vice-President. Well-linked information within LTM is more readily recalled than its poorly linked counterpart (Stein et al., 1984).

While elaboration fosters storage and retrieval, it is also a time-intensive process. Comprehending sentences necessitating elaboration mandates a greater duration than sentences not necessitating elaboration (Haviland & Clark, 1974). For instance, the subsequent sentences necessitate the inference that Marge conveyed her credit card to the emporium: “Marge ventured to the emporium,” and “Marge charged her merchandise.” The linkage is elucidated in the subsequent sentences: “Marge conveyed her credit card to the emporium,” and “Marge employed her credit card to remunerate for her merchandise.” The explicit establishment of linkages between contiguous propositions aids their encoding and retention.

A cardinal aspect of learning involves determining the significance of information. Not all assimilated information necessitates elaboration. Comprehension is aided when scholars elaborate solely upon the most salient facets of text (Reder, 1979). Elaboration aids retrieval by furnishing alternate pathways along which activation may propagate, thereby ensuring accessibility should one pathway be obstructed (Anderson, 1990, 2000). Elaboration also furnishes supplementary information from which answers may be constructed (Reder, 1982), as exemplified when scholars are tasked with addressing questions utilising information presented in a disparate form from that of the assimilated material.

In general, virtually all forms of elaboration aid encoding and retrieval; however, certain elaborations exhibit greater efficacy than others. Activities such as note-taking and enquiring as to the nexus between novel information and extant knowledge construct propositional networks. Effective elaborations link propositions and stimulate accurate recall. Elaborations lacking a robust nexus to the content fail to aid recall (Mayer, 1984).

Organisation transpires via the dissection of information into constituents and the specification of relationships therebetween. In the study of U.S. governance, organisation might entail dissecting governance into three branches (executive, legislative, judicial), dissecting each of these into sub-constituents (e.g., functions, agencies), et cetera. Older scholars employ organisation more frequently, yet elementary pupils are capable of employing organisational principles (Meece, 2002). Pupils scrutinising leaves may organise them according to size, shape, and edge pattern.

Organisation enhances retrieval by linking pertinent information; when retrieval is cued, spreading activation accesses pertinent propositions within LTM. Educators routinely organise material, yet student-generated organisation is also efficacious for retrieval. Instruction on organisational principles aids learning. Consider a schema for apprehending narratives encompassing four cardinal attributes: setting, theme, plot, and resolution (Rumelhart, 1977). The setting (“Once upon a time . . .”) situates the action within a context. Subsequently, the theme is introduced, comprising characters endowed with specific experiences and objectives. The plot traces the actions of the characters in their endeavour to attain their objectives. The resolution delineates how the objective is attained or how the characters adapt to its unattainability. By delineating and exemplifying these phases of a narrative, educators assist pupils in autonomously identifying them.

Retrieval of Procedural Knowledge

Retrieval of procedural knowledge mirrors that of declarative knowledge. Retrieval cues instigate associations within memory, and the process of spreading activation activates and recalls pertinent knowledge. Thus, should scholars be instructed to execute a given procedure within a chemistry laboratory, they will cue that production in memory, recall it, and implement it.

When declarative and procedural knowledge interact, retrieval of both is requisite. While adding fractions, scholars employ procedures (i.e., converting fractions to their lowest common denominator, adding numerators) and declarative knowledge (addition facts). During reading comprehension, certain processes operate as procedures (e.g., decoding, monitoring comprehension), whereas others involve solely declarative knowledge (e.g., word meanings, functions of punctuation marks). Individuals typically employ procedures to acquire declarative knowledge, such as mnemonic techniques to memorise declarative knowledge. The possession of declarative information is typically a prerequisite for the successful implementation of procedures. To resolve for roots utilising the quadratic formula, scholars must possess knowledge of multiplication facts.

Declarative and procedural knowledge exhibit tremendous variance in scope. Individuals possess declarative knowledge pertaining to the world, themselves, and others; they apprehend procedures for accomplishing diverse tasks. Declarative and procedural knowledge diverge in that procedures transform information. Such declarative statements as “ ” and “Uncle Fred smokes malodorous cigars” effect no change, whereas applying the long-division algorithm to a problem transforms an unsolved problem into a solved one.

An additional disparity resides in processing speed. Retrieval of declarative knowledge is frequently slow and conscious. Even presuming individuals possess the answer to a query, they may necessitate a period of cogitation to furnish it. For instance, contemplate the time necessitated to address “Who was the U.S. President in 1867?” (Andrew Johnson). In contrast, once procedural knowledge is ensconced in memory, its retrieval is rapid and often automatic. Accomplished readers decode printed text automatically; they are not compelled to consciously reflect upon their actions. Processing speed differentiates accomplished readers from their less proficient counterparts (de Jong, 1998). Upon mastering multiplication, we obviate the need to contemplate the steps necessary to resolve problems.

The disparities between declarative and procedural knowledge bear implications for pedagogy and learning. Scholars may encounter difficulty with a particular content area owing to a deficiency in domain-specific declarative knowledge or a lack of comprehension of prerequisite procedures. Ascertaining the nature of the deficiency constitutes a necessary initial step in the formulation of remedial instruction. Not only do deficiencies impede learning, but they also engender low self-efficacy. Scholars who possess an understanding of division but lack knowledge of multiplication facts become demoralised when consistently arriving at erroneous answers.

An application illustrating the storage and retrieval of information within Long-Term Memory (LTM) is to be found in language comprehension (Carpenter, Miyake, & Just, 1995; Corballis, 2006; Clark, 1994; Matlin, 2009). Language comprehension is of high relevance to scholastic learning, particularly in light of the increasing number of pupils whose native tongue is not English (Fillmore & Valadez, 1986; Hancock, 2001; Padilla, 2006).

Comprehending spoken and written language doth represent a problem-solving process involving domain-specific declarative and procedural knowledge (Anderson, 1990). Language comprehension hath three major components: perception, parsing, and utilisation. Perception involveth attending to and recognising an input; sound patterns are translated into words in working memory (WM). Parsing meaneth mentally dividing the sound patterns into units of meaning. Utilisation refereth to the disposition of the parsed mental representation: storing it in LTM if it be a learning task, giving an answer if it be a question, asking a question if it be not comprehended, and so forth. This section covereth parsing and utilisation; perception was discussed earlier in this lesson's seria.

Parsing

Linguistic research doth shew that persons understand the grammatical rules of their language, even though they usually cannot verbalise them (Clark & Clark, 1977). Beginning with the work of Chomsky (1957), researchers have investigated the role of deep structures containing prototypical representations of language structure. The English language containeth a deep structure for the pattern “noun 1–verb–noun 2,” which alloweth us to recognise these patterns in speech and interpret them as “noun 1 did verb to noun 2.” Deep structures may be represented in LTM as productions. Chomsky postulated that the capacity for acquiring deep structures is innately human, although which structures are acquired dependeth on the language of one’s culture.

Parsing includeth more than just fitting language into productions. When persons are exposed to language, they construct a mental representation of the situation. They recall from LTM propositional knowledge about the context into which they integrate new knowledge. A central point is that all communication is incomplete. Speakers do not provide all information relevant to the topic being discussed. Rather, they omit the information listeners are most likely to know (Clark & Clark, 1977). For example, suppose Sam meets Kira and Kira remarks, “You won’t believe what happened to me at the concert!” Sam is most likely to activate propositional knowledge in LTM about concerts. Then Kira says, “As I was locating my seat . . .” To comprehend this statement, Sam must know that one purchases a ticket with an assigned seat. Kira did not tell Sam these things because she assumed he knew them.

Effective parsing requireth knowledge and inferences (Resnick, 1985). When exposed to verbal communication, individuals access information from LTM about the situation. This information existeth in LTM as propositional networks hierarchically organised as schemas. Networks allow persons to understand incomplete communications. Consider the following sentence: “I went to the grocery store and saved five dollars with coupons.” Knowledge that persons buy merchandise in grocery stores and that they can redeem coupons to reduce cost enablith listeners to comprehend this sentence. The missing information is filled in with knowledge in memory.

Persons oft misconstrue communications because they fill in missing information with the wrong context. When given a vague passage about four friends getting together for an evening, music students interpreted it as a description of playing music, whereas physical education students described it as an evening of playing cards (Anderson, Reynolds, Schallert, & Goetz, 1977). The interpretative schemas salient in persons’ minds are used to comprehend problematic passages. As with many other linguistic skills, interpretations of communications become more reliable with development as children realise both the literal meaning of a message and its intent (Beal & Belgrad, 1990).

That spoken language is incomplete can be shewn by decomposing communications into propositions and identifying how propositions are linked. Consider this example (Kintsch, 1979):

The Swazi tribe was at war with a neighbouring tribe because of a dispute over some cattle. Among the warriors were two unmarried men named Kakra and his younger brother Gum. Kakra was killed in battle.

Although this passage seems straightforward, analysis revealeth the following 11 distinct propositions:

1. The Swazi tribe was at war.
2. The war was with a neighbouring tribe.
3. The war had a cause.
4. The cause was a dispute over some cattle.
5. Warriors were involved.
6. The warriors were two men.
7. The men were unmarried.
8. The men were named Kakra and Gum.
9. Gum was the younger brother of Kakra.
10. Kakra was killed.
11. The killing occurred during battle.

Even this propositional analysis is incomplete. Propositions 1 through 4 link together, as do Propositions 5 through 11, but a gap occurreth between 4 and 5. To supply the missing link, one might have to change Proposition 5 to “The dispute involved warriors.”

Kintsch and van Dijk (1978) shewed that features of communication influence comprehension. Comprehension becometh more difficult when more links are missing and when propositions are further apart (in the sense of requiring inferences to fill in the gaps). When much material hath to be inferred, WM becometh overloaded and comprehension suffereth.

Just and Carpenter (1992) formulated a capacity theory of language comprehension, which postulateth that comprehension dependeth on WM capacity and individuals differ in this capacity. Elements of language (e.g., words, phrases) become activated in WM and are operated on by other processes. If the total amount of activation available to the system is less than the amount required to perform a comprehension task, then some of the activation maintaining older elements will be lost (Carpenter et al., 1995). Elements comprehended at the start of a lengthy sentence may be lost by the end. Production-system rules presumably govern activation and the linking of elements in WM.

We see the application of this model in parsing of ambiguous sentences or phrases (e.g., “The soldiers warned about the dangers . . .”; MacDonald, Just, & Carpenter, 1992). Although alternative interpretations of such constructions initially may be activated, the duration of maintaining them dependeth on WM capacity. Persons with large WM capacities maintain the interpretations for quite a while, whereas those with smaller capacities typically maintain only the most likely (although not necessarily correct) interpretation. With increased exposure to the context, comprehenders can decide which interpretation is correct, and such identification is more reliable for persons with large WM capacities who still have the alternative interpretations in WM (Carpenter et al., 1995; King & Just, 1991).

In building representations, persons include important information and omit details (Resnick, 1985). These gist representations include propositions most germane to comprehension. Listeners’ ability to make sense of a text dependeth on what they know about the topic (Chiesi et al., 1979; Spilich et al., 1979). When the appropriate network or schema existeth in listeners’ memories, they employ a production that extracteth the most central information to fill the slots in the schema. Comprehension proceedeth slowly when a network must be constructed because it doth not exist in LTM.

Stories exemplify how schemas are employed. Stories have a prototypical schema that includes setting, initiating events, internal responses of characters, goals, attempts to attain goals, outcomes, and reactions (Black, 1984; Rumelhart, 1975, 1977; Stein & Trabasso, 1982). When hearing a story, persons construct a mental model of the situation by recalling the story schema and gradually fitting information into it (Bower & Morrow, 1990). Some categories (e.g., initiating events, goal attempts, consequences) are nearly always included, but others (internal responses of characters) may be omitted (Mandler, 1978; Stein & Glenn, 1979). Comprehension proceedeth quicker when schemas are easily activated. Persons recall stories better when events are presented in the expected order (i.e., chronological) rather than in a nonstandard order (i.e., flashback). When a schema is well established, persons rapidly integrate information into it. Research sheweth that early home literacy experiences that include exposure to books relate positively to the development of listening comprehension (Sénéchal & LeFevre, 2002)

Utilization

Utilisation referreth to what persons do with the communications they receive. For example, if the communicator asketh a question, listeners retrieve information from LTM to answer it. In a classroom, students link the communication with related information in LTM.

To use sentences properly, as speakers intend them, listeners must encode three pieces of information: speech act, propositional content, and thematic content. A speech act is the speaker’s purpose in uttering the communication, or what the speaker is trying to accomplish with the utterance (Austin, 1962; Searle, 1969). Speakers may be conveying information to listeners, commanding them to do something, requesting information from them, promising them something, and so on. Propositional content is information that can be judged true or false. Thematic content refereth to the context in which the utterance is made. Speakers make assumptions about what listeners know. On hearing an utterance, listeners infer information not explicitly stated but germane to how it is used. The speech act and propositional and thematic contents are most likely encoded with productions.

As an example of this process, assume that Jim Marshall is giving a history lesson and is questioning students about text material. Mr. Marshall asketh, “What was Churchill’s position during World War II?” The speech act is a request and is signalled by the sentence beginning with a WH word (e.g., who, which, where, when, and why). The propositional content referreth to Churchill’s position during World War II; it might be represented in memory as follows: Churchill–Prime Minister–Great Britain–World War II. The thematic content referreth to what the teacher left unsaid; the teacher assumeth students have heard of Churchill and World War II. Thematic content also includeth the classroom question-and-answer format. The students understand that Mr. Marshall will be asking questions for them to answer.

Of special importance for school learning is how students encode assertions. When teachers utter an assertion, they are conveying to students they believe the stated proposition is true. If Mr. Marshall says, “Churchill was the Prime Minister of Great Britain during World War II,” he is conveying his belief that this assertion is true. Students record the assertion with related information in LTM.

Speakers facilitate the process whereby persons relate new assertions with information in LTM by employing the given-new contract (Clark & Haviland, 1977). Given information should be readily identifiable and new information should be unknown to the listener. We might think of the given-new contract as a production. In integrating information into memory, listeners identify given information, access it in LTM, and relate new information to it (i.e., store it in the appropriate “slot” in the network). For the given-new contract to enhance utilisation, given information must be readily identified by listeners. When given information is not readily available because it is not in listeners’ memories or has not been accessed in a long time, using the given-new production is difficult.

Although language comprehension is oft overlooked in school in favour of reading and writing, it is a central component of literacy. Educators lament the poor listening and speaking skills of students, and these are valued attributes of leaders. Habit 5 of Covey’s (1989) Seven Habits of Highly Effective People is “Seek first to understand, then to be understood,” which emphasizeth listening first and then speaking. Listening is intimately linked with high achievement. A student who is a good listener is rarely a poor reader. Among college students, measures of listening comprehension may be indistinguishable from those of reading comprehension (Miller, 1988).

We are wont to forget a great deal, notwithstanding our best intentions. Forgetting doth refer to the loss of information from the memory, or to the inability to gain access unto such information. Researchers are not in accord as to whether information be lost from memory altogether, or whether it yet remains present, albeit its retrieval be impeded by distortion, inadequate retrieval cues, or the interference of other information with its recall. The matter of forgetting hath been studied experimentally since the days of Ebbinghaus. Prior to presenting information processing perspectives on forgetting, which involve interference and decay, let us consider some historical work on interference.

Interference Theory

One of the signal contributions of the verbal learning tradition was the interference theory of forgetting. According to this theory, learned associations are never entirely forgotten. Forgetting springs from competing associations, which serve to lower the probability of the correct association being recalled; that is to say, other material becomes associated with the original stimulus (Postman, 1961). The crux of the matter lies in retrieving information from memory, rather than in the memory itself (Crouse, 1971).

Two distinct types of interference have been experimentally identified (Table 'Interference and forgetting'). Retroactive interference occurs when new verbal associations render the remembering of prior associations difficult. Proactive interference, on the other hand, refers to older associations that make newer learning more difficult.

To demonstrate retroactive interference, an experimenter might request two groups of individuals to learn Word List A. Group 1 then learns Word List B, whilst Group 2 engages in a competing activity to forestall rehearsal of List A. Thereafter, both groups attempt to recall List A. Retroactive interference occurs should the recall of Group 2 prove superior to that of Group 1. For proactive interference, Group 1 learns List A, whilst Group 2 does naught. Both groups then learn List B and attempt to recall List B. Proactive interference occurs should the recall of Group 2 surpass that of Group 1.

Retroactive and proactive interference occur frequently in the scholastic setting. Retroactive interference may be observed among students who learn words with regular spellings, and subsequently learn words that are exceptions to spelling rules. If, after some time, they are tested on the original words, they might alter the spellings to conform to those of the exceptions. Proactive interference is evident among students taught first to multiply, and then to divide, fractions. When subsequently tested on division, they may simply multiply without first inverting the second fraction. Developmental research doth reveal that proactive interference diminishes between the ages of 4 and 13 (Kail, 2002). Application 'Interference in Teaching and Learning' offers suggestions for dealing with interference.

Interference theory represented an important step in specifying memory processes. Early theories of learning posited that learned connections leave a memory “trace” that weakens and decays with nonuse. Skinner (1953) did not postulate an internal memory trace, but suggested that forgetting results from lack of opportunity to respond, due to the stimulus being absent for some time. Each of these views hath shortcomings. Although some decay may occur (discussed later), the notion of a memory trace is vague and difficult to verify experimentally. The nonuse position holds at times, but exceptions do exist; for example, being able to recall information after many years of nonuse (e.g., names of some elementary school teachers) is not unusual. Interference theory surmounts these problems by positing how information in memory becomes confused with other information. It also specifies a research model for investigating these processes.

Postman and Stark (1969) suggested that suppression, rather than interference, causeth forgetting. Participants in learning experiments retain in active memory material they believe they will need to recall later. Those who learn List A, and then are given List B, are apt to suppress their responses to the words on List A. Such suppressions would endure whilst they are learning List B, and for a while thereafter. In support of this point, the typical retroactive interference paradigm produces scant forgetting when learners are given a recognition test on the original Word List A, rather than being asked to recall the words.

Tulving (1974) posited that forgetting represents inaccessibility of information, owing to improper retrieval cues. Information in memory doth not decay, become confused, or get lost. Rather, the memory trace is intact, but cannot be accessed. Memory of information dependeth upon the trace being intact, and upon having adequate retrieval cues. Perchance you cannot remember your home telephone number from many years ago. You may not have forgotten it; the memory is submerged because your current environment differs from that of years ago, and the cues associated with your old home telephone number—your house, street, neighbourhood—are absent. This principle of cue-dependent forgetting is also compatible with the common finding that people perform better on recognition tests than on recall tests. In the cue-dependent view, they ought to perform better in recognition tests because more retrieval cues are provided; in recall tests, they must supply their own cues.

Later research on interference suggesteth that interference occurreth (e.g., people confuse elements) when the same cognitive schema or plan is used on multiple occasions (Thorndyke & Hayes-Roth, 1979; Underwood, 1983). Interference theory continueth to provide a viable framework for investigating forgetting (Brown, Neath, & Chater, 2007; Oberauer & Lewandowsky, 2008).

Information Processing

From an information processing perspective, interference referreth to a blockage of the spread of activation across memory networks (Anderson, 1990). For various reasons, when people attempt to access information in memory, the activation process is thwarted. Although the mechanism blocking activation is not completely understood, theory and research suggest various causes of interference.

One factor that can affect whether structures are activated is the strength of original encoding. Information that originally is strongly encoded through frequent rehearsal or extensive elaboration is more likely to be accessed than information that originally is weakly encoded.

A second factor is the number of alternative network paths down which activation can spread (Anderson, 1990). Information that can be accessed via many routes is more likely to be remembered than information that is only accessible via fewer paths. For example, if I want to remember the name of Aunt Frieda’s parakeet (Mr. T), I should associate that with many cues, such as my friend Mr. Thomas, the fact that when Mr. T spreads his wings it makes the letter T, and the idea that his constant chirping taxes my tolerance. Then, when I attempt to recall the name of the parakeet I can access it via my memory networks for Aunt Frieda and for parakeets. If these fail, then I still have available the networks for my friends, the letter T, and things that tax my tolerance. In contrast, if I associate only the name “Mr. T” with the bird, then the number of alternative paths available for access is fewer and the likelihood of interference is greater.

A third factor is the amount of distortion or merging of information. Throughout this lesson we have discussed the memory benefits of organising, elaborating, and making information meaningful by relating it to what we know. Whenever we engage in these practices, we change the nature of information, and in some cases we merge it with other information or subsume it under more general categories. Such merging and subsumption facilitate meaningful reception learning (Ausubel, 1963, 1968; discussed later in this lesson). Sometimes, however, such distortion and merging may cause interference and make recall more difficult than if information is remembered on its own.

Interference is an important cause of forgetting, but it is unlikely that it is the only one (Anderson, 1990). It appears that some information in LTM decays systematically with the passage of time, and independently of any interference. Wickelgren (1979) traced systematic decay of information in time intervals ranging from 1 minute to 2 weeks. The data decay rapidly at first, with decay gradually tapering off. Researchers find little forgetting after 2 weeks.

The position that forgetting occurs because of decay is difficult to affirm or refute. Failure to recall, even with extensive cuing, doth not unequivocally support a decay position, because it still is possible that the appropriate memory networks were not activated. Similarly, the fact that the decay position posits no psychological processes responsible for forgetting (rather only the passage of time) doth not refute the position. Memory traces include both perceptual features and reactions to the experiences (Estes, 1997). Decay or changes in one or both causeth forgetting and memory distortions. Furthermore, the decay process may be neurological (Anderson, 1990). Synapses can deteriorate with lack of use, in the same way muscles do with nonuse.

Decay is commonly cited as a reason for forgetting (Nairne, 2002). You may have learned French in high school, but now, some years later, cannot recall many vocabulary words. You might explain that as, “I haven’t used it for so long that I’ve forgotten it.” Furthermore, forgetting is not always bad. Were we to remember everything we have ever learned, our memories would be so overcrowded that new learning would be very difficult. Forgetting is facilitative when it rids us of information that we have not used, and thus may not be important, analogous to your discarding things that you no longer need. Forgetting leadeth people to act, think, judge, and feel differently than they would in the absence of forgetting (Riccio, Rabinowitz, & Axelrod, 1994). Forgetting hath profound effects on teaching and learning (Application 'Minimising Forgetting of Academic Learning').