Interference theory

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.<ref name = Edwards>Edwards, W. H. (2010). Motor Learning and Control: From Theory to Practice. Belmont, CA: Cengage Learning.</ref> 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.<ref name="Edwards"/> Retaining information regarding the relevant time of encoding memories into LTM influences interference strength.<ref name="Edwards"/> There are two types of interference effects: proactive and retroactive interference.

History

John A. Bergström is credited with conducting the first study regarding interference in 1892. His experiment was similar to the Stroop task and required subjects to sort two decks of cards with words into two piles. When the location was changed for the second pile, sorting was slower, demonstrating that the first set of sorting rules interfered with learning the new set.<ref name=Rieber>Template:Cite book</ref> German psychologists continued in the field with Georg Elias Müller and Pilzecker in 1900 studying retroactive interference. To the confusion of Americans at a later date, Müller used "associative Hemmung" (inhibition) as a blanket term for retroactive and proactive inhibition.<ref name="Rieber"/>

The next major advancement came from American psychologist Benton J. Underwood in 1957. Underwood revisited the classic Ebbinghaus learning curve and found that most of the forgetting was due to interference from previously learned materials.<ref>Underwood, B. J. (1957). Interference and forgetting. Psychological Review, 64(1), 49.</ref>

In 1924, John G. Jenkins and Karl Dallenbach showed that everyday experiences can interfere with memory, employing an experiment that showed that retention was better throughout sleep than over the same amount of time devoted to the activity.<ref name = Hilgard>Template:Cite book</ref> The United States again made headway in 1932 with John A. McGeoch suggesting that decay theory should be replaced by an interference theory.<ref name="Hilgard"/> The most recent major paradigm shift came when Underwood proposed that proactive inhibition is more important or meaningful than retroactive inhibition in accounting for forgetting.<ref>Template:Cite book</ref>

Proactive interference

Proactive interference is the interference of older memories with the retrieval of newer memories.<ref name="Edwards"/> Of the two effects of interference theory, proactive interference is the less common and less problematic type of interference compared to retroactive interference.<ref name="Edwards"/> Previously, it had been hypothesized that forgetting working memories would be nonexistent if not for proactive interference.<ref>Template:Cite journal</ref>

Context

Proactive interference build-up occurs with memories being learned in similar contexts. A common example is observing previous motor abilities from one skill interfering with a new set of motor abilities being learned in another skill from the initial.<ref name="Edwards"/> Proactive interference is also associated with poorer list discrimination, which occurs when participants are asked to judge whether an item has appeared on a previously learned list.<ref>Template:Cite journal</ref> If the items or pairs to be learned are conceptually related to one another, then proactive interference has a greater effect.<ref>Template:Cite journal</ref> Delos Wickens discovered that proactive interference build-up is released when there is a change to the category of items being learned, leading to increased processing in STM.<ref name="Wickens main">Template:Cite journal</ref> Presenting new skills later in practice can considerably reduce proactive interference desirable for participants to have the best opportunity to encode fresh new memories into LTM.<ref name="Edwards"/>

File:Prefrontal cortex.png

Prefrontal cortex

Brain structures

The leading experimental technique for studying proactive interference in the brain is the "recent-probes" task. Initially, this is when participants must commit a set of items to memory. They then ask them to recall a specific item. Assessing them is shown by a probe.<ref name=jonides>Template:Cite journal</ref> Thus, using recent-probes task and fMRIs, the brain mechanisms involved in resolving proactive interference identify as the ventrolateral prefrontal cortex and the left anterior prefrontal cortex.<ref>Template:Cite journal</ref>

Research

With lists

Researchers have studied the joint influence of proactive and retroactive interference using a list of items to be remembered. As expected, the recall was hampered by increasing the number of items in a given list.<ref>Template:Cite journal</ref> Proactive interference also affected learning when dealing with multiple lists. Researchers had participants learn a list of ten paired adjectives.<ref>Template:Cite journal</ref> The experimenters would consider a list to be learned if the participant could correctly recall eight of the ten items. After two days, participants could recall close to 70% of the items. However, those asked to memorize a new list the day after learning the first one had a recall of only 40%. Those who learned a third list recalled 25% of the items. Therefore, proactive interference affected the correct recall of the last list learned, because of the previous one, or two. In terms of forgetting, the effect of proactive interference was supported by further studies using different methods.<ref>Template:Cite journal</ref> The effect of proactive interference was reduced when the test was immediate and when the new target list was different from the previously learned lists.

Span performance

Span performance refers to working memory capacity. It is hypothesized that span performance is limited in language comprehension, problem-solving, and memory.<ref name=may>Template:Cite journal</ref> Proactive Interference affects susceptibility to span performance limitations, as span performance in later experimental trials were worse than performance in earlier trials.Template:Clarify<ref name=may /><ref>Template:Cite journal</ref> With single tasks, proactive interference had less effect on participants with high working memory spans than those with low ones. With dual tasks, both types were similarly susceptible.

To differ, others have tried to investigate the relation of proactive interference when cued to forget. Turvey and Wittlinger designed an experiment to examine the effects of cues such as "not to remember" and "not to recall" with currently learned material. While "not to remember" had a significant effect in reducing proactive interference, cued to "not to recall" previously encoded and stored information did not significantly reduce the effect. Therefore, these associated cues do not directly control the potential effect of proactive interference on short-term memory span.Template:Clarify<ref>Template:Cite journal</ref>

Proactive interference has shown an effect during the learning phase in terms of stimuli at the acquisition and retrieval stages with behavioral tasks for humans, as found by Castro, Ortega, and Matute.<ref>Template:Cite journal</ref> With 106 participants, they investigated two main questions: if two cues are learned as predictors of the same outcome (one after the other), would the second-cue outcome association be retarded? And secondly, once the second association is fully learned, will there still be an effect on subsequent trials? The research, as predicted, showed retardation and impairment in associations, due to the effect of Proactive Interference.

Retroactive interference

Retroactive interference, also known as Retroactive inhibition, is the interference of newer memories with the retrieval of older memories.<ref name="Edwards"/> In other words, subsequently learned memories directly contributes to the forgetting of previously learned memories. The effect of retroactive interference takes place when any type of skill has not been rehearsed over long periods.<ref name="Edwards"/> Of the two effects of interference theory, retroactive interference is considered the more common and more problematic type of interference compared to proactive interference.<ref name="Edwards"/>

RI is a classic paradigm that was first officially termed by Muller.<ref name = Muller>Template:Cite journal</ref> These memory research pioneers demonstrated that filling the retention interval (defined as the amount of time that occurs between the initial learning stage and the memory recall stage) with tasks and material caused significant interference effects with the primary learned items.

As compared to proactive interference, retroactive interference may have larger effects because there is not only competition involved but also unlearning.<ref>Template:Cite journal</ref>

Iconic research

Modified (free) recall

Briggs's (1954) study modeled McGeoch's work on interference by setting the stage for a classic design of retroactive interference. In his study, participants were asked to learn 12 paired associates to a criterion of 100%. To ensure parsimony, these pairs can be labeled as A₁-B₁-, A₂-B₂-...A _I -B _I (also called AB/AC paradigm). Briggs used a "modified free recall" technique by asking participants to recall an item when cued with B _I . Over multiple anticipation trials, participants learned B _I items through the prompt of B _I items. After perfecting A _I - B _I learning, participants were given a new list of paired associates to learn; however B _I items were replaced with C _I items (now given a list of A₁-C₁-, A₂-C₂-...A _I -C _I ). As the learning of A _I -C _I pairs increased, the learning of A _I -B _I pairs decreased. Eventually recalling the C _I items exceeded the recall of the B _I items, representing the phenomenon of retroactive interference. A significant part of Briggs's (1954) study was that once participants were tested after a delay of 24 hours the Bi responses spontaneously recovered and exceeded the recall of the Ci items. Briggs explained the spontaneous recovery illustration as an account of A _I -B _I items competing with A _I -C _I items or, as McGeoch would define it: "a resultant [of] momentary dominance".<ref name = Briggs>Template:Cite journal</ref>

Modified modified free recall

J.M. Barnes and B.J. Underwood (1959) expanded Briggs's (1954) study by implementing a similar procedure. The main difference in this study, however, was that, unlike Briggs's (1954) "modified free recall" (MFR) task where participants gave one-item responses, Barnes and Underwood asked participants to give both List 1 and List 2 responses to each cued recall task. Participants' ability to recall both items was termed the "modified modified free recall" (MMFR) technique. Equivocally to Briggs's (1954) results, RI occurred when C _I recalled responses gradually came to exceed B _I responses. Barnes and Underwood argued that because there was "unlimited recall time" to produce multiple-item responses, the fact that A _I -C _I responses still trumped A _I -B _I responses represented an account of unlearning.<ref name = barns>Template:Cite journal</ref>

Notable research concepts

Forgetting

Since German psychologist H. Ebbinghaus (1885, 1913) made the first scientific studies on forgetting in the late nineteenth century, further research on the rate of forgetting presented information was found to be steep.<ref name="Edwards"/> While a variety of factors play a role in affecting the rate of forgetting, the general conclusion made is that 70% of originally recalled information is initially forgotten in 24 hours after a session of practice, followed by 80% of information forgotten within 48 hours.<ref name="Edwards"/> Afterwards, forgetting diminishes at a gradual rate, which leaves about 5% to 10% of retained information available for learners to access from practice until the next session.<ref name="Edwards"/> Despite the numbers, retroactive interference can be reduced significantly by implementing over-learning practice schedules, periodic refresh sessions when practicing skills, and skill rehearsal time for the inactive periods of practicing.<ref name="Edwards"/> Continuous skills are more resistant to the rate of forgetting compared to discrete skills, which indicates that the types of skills being practiced and retroactive interference significantly interact with one another.<ref name="Edwards"/>

Theories

The phenomenon of retroactive interference is highly significant in the study of memory as it has sparked a historical and ongoing debate in regards to whether the process of forgetting is due to the interference of other competing stimuli, or rather the unlearning of the forgotten material. The important conclusion one may gain from RI is that "forgetting is not simply a failure or weakness of the memory system" (Bjork, 1992), but rather an integral part of our stored knowledge repertoire. Although modern cognitive researchers continue to debate the actual causes of forgetting (e.g., competition vs. unlearning), retroactive interference implies a general understanding that additional underlying processes play a role in memory.

Competition

A standard explanation for the cause of RI is Competition. New associations compete with older associations and the more recent association would win out making it impossible to remember earlier associations. Spontaneous Recovery in MFR supports the claim of competition since after a rest period participants spontaneously remembered original pair associations that they were not able to remember right after the second test.<ref name="Briggs"/>

Associative unlearning

The associative unlearning hypothesis explains RI by saying that new associations replace the old associations in memory causing the participant to forget the initial associations. Barnes and Underwood argued that A _I -C _I responses still outnumber A _I -B _I responses after the delay period supports the Associative Unlearning Hypothesis over Competition.<ref name="barns"/>

Brain structures

Retroactive Interference has been localized to the left anterior ventral prefrontal cortex by magnetoencephalography (MEG) studies investigating Retroactive Interference and working memory in elderly adults.<ref name = Solesio>Template:Cite journal</ref> The study found that adults 55–67 years of age showed less magnetic activity in their prefrontal cortices than the control group. Executive control mechanisms are located in the frontal cortex and deficits in working memory show changes in the functioning of this brain area.<ref name="Solesio"/>

Research

Pitch perception

Retroactive Interference has also been investigated using pitch perception as the learning medium.<ref name = Massaro>Template:Cite journal</ref> The researcher found that the presentation of subsequent stimuli in succession causes a decrease in recalled accuracy.<ref name="Massaro"/> Massaro found that the presentation of successive auditory tones, confused perceptual short-term memory, causing Retroactive Interference as the new tone inhibits the retrieval of previously heard tones.<ref name="Massaro"/>

Motor movement

Wohldmann, Healey, and Bourne found that Retroactive Interference also affects the retention of motor movements.<ref name = Wohldmann>Template:Cite journal</ref> Researchers found that retroactive interference affects the performance of old motor movements when newly acquired motor movements are practiced.<ref name="Wohldmann"/> Physical practice of newly executed motor movements decreased the retention and recall of previously learned movements.<ref name="Wohldmann"/> Despite the retroactive interference noted by Wohldmann et al., researchers noted that mental practice decreased the amount of retroactive interference, suggesting that mental practice is more flexible and durable over time.<ref name="Wohldmann"/> This study of the superiority effect of physical practice is similar to the Word Superiority Effect made famous by Cattell.<ref>Template:Cite journal</ref>

Word tasks

Retroactive Interference increases when the items are similar, therefore increasing association between them as shown by spreading activation.<ref name = Barnes>Template:Cite journal</ref> Barnes and Underwood found that when participants in the experimental condition were presented with two similar word lists, the recollection of the first-word list decreased with the presentation of the second-word list.<ref name="Barnes"/> This finding contrasts the control condition as they had little Retroactive Inference when asked to recall the first-word list after a period of unrelated activity.<ref name="Barnes"/>

Output interference

Output Interference occurs when the initial act of recalling specific information interferes with the retrieval of the original information.<ref>Template:Cite journal</ref> An example scenario in which Output Interference might occur would be if one had created a list of items to purchase at a grocery store, but then, neglected to take the list when leaving home. The act of remembering a couple of items on that list decreases the probability of remembering the other items on that list.

Research

Short-term memory

Henry L. Roediger III and Schmidt found that the act of retrieval can serve as the source of the failure to remember, using multiple experiments that tested the recall of categorized and paired associative lists.<ref name = Roediger>Template:Cite journal</ref> Three experiments were carried out where subjects were first presented with category lists, and then, asked to recall the items in the list after being shown the category name as a cue.<ref name="Roediger"/> The further the test position from the category resulted in a decline of the recall of words. A fourth experiment revealed that only recent items were present in output interference in paired associative lists.<ref name="Roediger"/>

File:Gray739-emphasizing-hippocampus.png

Hippocampus highlighted in blue

File:Amygdala.gif

Amygdala highlighted in red

Long-term memory

Smith found that if categories with corresponding items were successfully recalled, a systematic decline would occur when recalling the items in a category across the output sequence.<ref name = "Smith, A.D.(1971)">Template:Cite journal</ref> He conducted multiple experiments to determine the input conditioned necessary to produce Output Interference.<ref name="Smith, A.D.(1971)"/> In his first experiment word recall per category was greater at 60 sec than 30 sec when taking the last input category out to prevent recency effect.<ref name="Smith, A.D.(1971)"/> In his second experiment he changed the instructions, words used, and nature of the retention test, and showed with the recognition procedure, there was Output Interference but the effect was limited to the first three output positions.<ref name="Smith, A.D.(1971)"/> Even if retrieving items is necessary for a recall, it is not crucial to performance in a recognition tack.<ref name="Smith, A.D.(1971)"/> Recall of the organized information from long-term memory hurt the following item recalled.<ref name="Smith, A.D.(1971)"/> In long-term memory, Smith suggests that Output Interference has effects on extra-core material, which is represented as contextual information, rather than the core material, which is highly available as a result of organization.<ref name="Smith, A.D.(1971)"/>

Effects of age

In both short-term memory and long-term memory Smith measured output interference in three age groups (aged 20–39, 40–59, 60–80 years).<ref name = Smith2>Template:Cite journal</ref> The results of recall performance revealed significant differences due to age where the older group recalled fewer items than the middle group who recalled fewer items than the youngest group.<ref name="Smith2"/> Overall Smith concluded that memory decline appears with increased age with long-term memory forgetting rather than short-term memory forgetting and short-term memory was unaffected by age. However, output interference was unable to explain the memory deficit seen in older subjects.<ref name="Smith2"/>

Recent research of adults free recall and cognitive triage displayed similar findings of recall performance being poorer in older adults compared to younger adults.<ref name= Marche>Template:Cite journal</ref> Although it was also indicated that older adults had an increased susceptibility to output interference compared to younger adults and the difference increased as additional items were recalled.<ref name="Marche"/>

Similar theories

Decay theory

Decay theory outlines that memories weaken over time despite consolidation and storage.<ref>Baddeley, A., Eysenck, M.W. & Anderson, A.C. (2009). Memory. New York, NY: Psychology Press</ref> This is to say that although you remember a specific detail, over time you may have greater difficulty retrieving the detail you encoded. It has been suggested that the time interval between encoding and retrieval determines the accuracy of recall.<ref>Template:Cite journal</ref>

A practical example of decay theory is seen in the financial sector. If you open a bank account and do not deposit or withdraw money from the account, after some time, the bank will render the account dormant. The owner of the account, then, has to reopen the account for it to remain active. The bank account (the memory) is rendered dormant (the memory weakened) over time if there is no activity on the account (if the memory is not retrieved after some time).

Similarities

Decay theory is similar to interference theory in the way that old memories are lost over time. Memories are lost in Decay Theory by the passing of time. In Interference Theory, memories are lost due to newly acquired memories. Both Decay and Interference Theories are involved in psychological theories of forgetting.

Differences

Decay and interference theory differ in that Interference Theory has a second stimulus that impedes the retrieval of the first stimulus. Decay Theory is caused by time itself. Decay Theory is a passive method of forgetting as no interference is produced.<ref>Grossberg, S. (1987) The Adaptive Brain: Vision, Speech, Language and Motor Control. Amsterdam, Netherlands: Elsevier</ref> Interference Theory is an active process because the act of learning new information directly impedes the recollection of previously stored information.

Dual task interference

Dual-task interference is a kind of interference that occurs when two tasks are attempted simultaneously. Harold Pashler wrote a paper summing up the theoretical approaches to dual-task interference.<ref name = Pashler>Template:Cite journal</ref> The basis of his research looked at when one attempts two or more tasks at the same time, why in some cases is one successful in completing their task and in other cases not.<ref name="Pashler"/>

Capacity sharing

Pashler proposed that the brain contains one mental entity where all tasks must be carried out.<ref name="Pashler"/> A real-life example of this could be going to the dentist; the only place to have cavities filled is at a dentist's office. When the brain is attempting to complete two tasks, both tasks are present in the same mind area and compete for processing ability and speed.<ref name="Pashler"/> This relates to interference theory as the tasks compete. Interference theory says that the learning of new information decreases the retrieval of older information, and this is true for dual-task interference. The dominant task of the two inhibits the other task from completion. It is presumed that the dominant task would be a new task as a previously accomplished task would already be stored in memory. The new task would, then, be completed successfully as more mental effort is required to complete a novel task, and the previously completed task would not be completed as the new task dominated the mental capacity. Just as Interference Theory states, the completion of new tasks inhibits the completion of previously completed tasks due to capacity sharing.

Cross talk models

Cross-talk is the communication between sensory inputs, processing, and the thoughts of the individual.<ref name="Pashler"/> The theory is that if two processes are being activated, and they are not similar in any way (making cookies and going on vacation), the brain will be confused as separate cognitive areas are being activated, and there is conflicting communication between the two.<ref name="Pashler"/> Contrastingly, if the two processes are similar (making cookies and pouring milk), there will be less crosstalk and more productive and uninterrupted cognitive processing.<ref name="Pashler"/>

Crosstalk is used by engineers to discuss the degradation of communication channels due to context dependence.<ref name="Pashler"/>

Navon and Miller claim that Dual-Task Interference is caused by an outcome conflict, which is a result of one task producing, "outputs, throughputs, or side effects that are harmful to the processing of the [other task]".<ref>Template:Cite journal</ref> This is the concept of Interference Theory. The thoughts, outputs, and side effects of one task either affect the previous or subsequent recall.

Neurobiology

File:MRI brain.jpg

MRI of a human brain

Event-related fMRI studies

File:Caudate nucleus.png

Caudate Nucleus highlighted in red

Stroop and Simon task

The performance of Stroop and Simon tasks were monitored on 10 healthy young adults using magnetic resonance image (MRI) scanning.<ref name = Peterson>Template:Cite journal</ref> Functional images were acquired at specific time intervals during each subject's scan.<ref name="Peterson"/> Brain activation during the Stroop and Simon task was remarkably similar including anterior cingulate, supplementary motor cortex, visual association cortex, inferior temporal cortex, inferior parietal cortex, inferior frontal cortex, dorsolateral prefrontal cortex, and caudate nuclei.<ref name="Peterson"/> Interference effects in the Stroop and Simon tasks activate similar brain regions at similar time distributions.<ref name="Peterson"/>

Application

Advertising

It has been demonstrated that recall will be lower when consumers have afterward seen an ad for a competing brand in the same product class. Exposure to later similar advertisements does not cause interference for consumers when brands are rated on purchasing likelihood. This shows that information processing objective can moderate the effects of interference of competitive advertising. Competitive brand advertising not only interferes with consumer recall of advertising in the past but also interferes with learning new distinctive brand information in the future.<ref>Template:Cite journal</ref>

Reducing competitive ad interference

Repetition improves brand name recall when presented alone. When competitive advertising was presented, it was shown that repetition provided no improvement in brand name recall over a single exposure. The competitive ads interfered with the added learning from repetition. However, when the target brand name was shown using varying ad executions interference was reduced. Presenting ads in multi-modalities (visual, auditory) will reduce possible interference because there are more associations or paths to cue recall than if only one modality had been used. This is the principle of multimedia learning. Also, interference is increased when competing ads are presented in the same modality. Therefore, by presenting ads in multiple modalities, the chance that the target brand has unique cues is increased.<ref>Template:Cite journal</ref>

See also

• Neuroimaging
• Working memory
• Memory inhibition
• Memory conformity
• Einstellung effect
• Language transfer (interference between languages)
• Forgetting curve
• Between-systems memory interference model

References

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• Bjork, R. A. (1992). Interference and memory. In L. R. Squire (Ed.), Encyclopedia of learning and memory (pp. 283–288). New York: Macmillan.
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