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Interference theory (also known as retrieval interference (Roediger & Karpicke, 2006)) refers to the idea that forgetting occurs because the recall of certain items interferes with the recall of other items. Generally speaking the interference causes slower learning and poorer memory.

Interference theory is an aspect of memory stating that interference occurs in learning when their is an interaction between the new material and the negative transfer effects of past learned behavior, memories or thoughts.[1]. This has the effect of impairing both the speed of learning and memory performance.

There are three main kinds of interference:

The main assumption of interference theory is that the stored memory is intact but unable to be retrieved due to competition created by newly acquired information.[1]


Bergström, a German psychologist, is credited as conducting the first study regarding interference in 1892. His experiment was similar to the Stroop task and required subjects to sort two decks of card 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.[2] German psychologists continued in the field with Georg Elias Müller and Pilzeker 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.[2]

The next major advancement came from American psychologist Benton J. Underwood in 1915. Underwood found that as the number lists learned increased, the retention of the last list learned decreased after 24 hours.[3]

In 1924, James J. Jenkins and Dallenback showed that everyday experiences can interfere with memory with an experiment that resulted in retention being better over a period of sleep than over the same amount of time devoted to activity.[3] The United States again made headway in 1932 with John A. McGeoch suggesting that decay theory should be replaced by an interference theory.[3] 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.[4]

In the late 1950s two groups of researchers published very similar methods that demonstrated the interference theory, a husband and wife team, Peterson and Peterson and another researcher, Brown.

In one study done by Peterson and Peterson participants were asked to recall trigrams (string of three letters) at different time intervals after the presentation of the last letter in the trigram. To make the trigrams impossible to pronounce the investigator used only consonants (e.g., BWV). The participants were asked to count backwards to allow no time for rehearsal and for the numbers to interfere with the recall of trigrams. Each of the participants were tested eight times at each of the six delay intervals which totaled to 48 trials. The percentage of recalls decays over time due to interference of the numbers they had to count backwards. From this study Peterson and Peterson concluded that short term memory exists for a few seconds if the participant does not make an active effort to retain the information."

This theory along with the decay theory have been proposed as reasons for why people forget. Evidence for this theory comes from paired associate learning, as well as from Jenkins and Dallenbach's 1924 experiment where they researched forgetting in two students over the period of eight hours.

Proactive inhibition

Proactive interference is the "forgetting [of information] due to interference from the traces of events or learning that occurred prior to the materials to be remembered."[5] Proactive interference occurs when in any given context, past memories inhibit an individual’s full potential to retain new memories. It has been hypothesized that forgetting working memories would be non-existent if not for proactive interference.[6]

Retroactive inhibition

Retroactive interference (RI) is a phenomenon that occurs when newly learned information interferes with and impedes the recall of previously learned information.[7] RI is a result of decreased recall of the primary studied functions due to the learning and recall of succeeding functions [8] RI is a classic paradigm that was first officially termed by Muller.[9] 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.

If compared to retroactive interference, studies show that Retroactive interference can have larger effects because of the fact that there is not only competition involved, but also unlearning.[10]

Output interference

Output Interference occurs when the initial act of recalling specific information interferes with the retrieval of the original information.[11] 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 forgot to take the list when leaving home. The act of remembering a couple items on that list decreases the probability of remembering the other items on that list.


Short-term memory

Henry L. Roediger III and Schmidt found that the act of retrieval can serve as the source of the failing to remember, using multiple experiments that tested the recall of categorized and paired associative lists.[12] 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.[12] 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.[12]


Hippocampus highlighted in blue


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.[13] He conducted multiple experiments to determine the input conditioned necessary to produce Output Interference.[13] 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.[13] In his second experiment he changed the instructions, words used, and nature of the test for retention, and showed with recognition procedure, there was Output Interference but the effect was limited to the first three output positions.[13] Even if retrieving items is necessary for recall, it is not crucial to performance in a recognition tack.[13] Recall of the organized information from long-term memory had a negative effect on the following item recalled.[13] In long-term memory, Smith suggests that Output Interference has effects on extra-core material, which is represented as contextual information, rather than core material, which is highly available as a result of organization.[13] Both short and long term memories are centralized to the hippocampus and the amygdala.[citation needed]

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).[14] 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.[14] 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 subject.[14]

Recent research of adult’s free recall and cognitive triage displayed similar findings of recall performance being poorer in older adults compared to younger adults.[15] 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.[15]

Similar theories

Decay theory

Decay theory outlines that memories weaken over time despite consolidation and storing.[16] 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.[17]

A practical example of decay theory is seen in the financial sector. If you open a bank account and not deposit or withdraw money from the account, after a period of 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 not activity on the account (if the memory is not retrieved after a period of time).


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.


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.[18] Interference Theory is an active process because the act of learning new information directly impedes the recollection of previously stored information.

Dual task interfence

Dual task interference is a kind of interference that occurs when two tasks are attempted simultaneously. Harold Pashler from McMaster University in Hamilton, Ontario Canada wrote a paper summing up the theoretical approaches to Dual Task Interference.[19] The basis of his research looked at, when one attempts two or more tasks at the same time, why in some cases are they successful in completing their task and in other cases not.[19]

Capacity sharing

Pashler proposed that the brain contains one mental entity to where all tasks must be carried out.[19] 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.[19] 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 in 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 successfully be completed as more mind 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.[19] 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.[19] Contrastingly, if the two processes are similar (making cookies and pouring milk), there will be less cross talk and a more productive and uninterrupted cognitive processing.[19]

Cross talk is used by engineers to discuss the degradation of communication channels due to context dependence.[19]

Navon and Miller claim that Dual Task Interference is caused by 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]".[20] This is basically the concept of Interference Theory. The thoughts, outputs and side effects of one task either effect the previous or subsequent recall.


MRI brain

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.[21] Functional images were acquired at specific time intervals during each subject's scan.[21] 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.[21] Interference effects in the Stroop and Simon tasks activate similar brain regions at similar time distributions.[21]



It has been demonstrated that recall will be lower when consumers have afterwards 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.[22]

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 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.[23]

See also


  1. 1.0 1.1 Tomlinson, T. D., Huber, D. E.; Rieth, C. A.; Davelaar, E. J. (26 August 2009). An interference account of cue-independent forgetting in the no-think paradigm. Proceedings of the National Academy of Sciences 106 (37): 15588–15593.
  2. 2.0 2.1 (1998) Psychology theoretical-historical perspectives, 2nd, Washington, DC: American Psychological Association.
  3. 3.0 3.1 3.2 Hilgard, Ernest R. (1987). Psychology in America : a historical survey, San Diego: Harcourt Brace Jovanovich.
  4. Neel, Ann (1977). Theories of Psychology: a handbook, Revised and enlarged, Cambridge: Schenkman Publishing Company.
  5. Still, A. W. (1 November 1969). Proactive interference and spontaneous alternation in rats. Quarterly Journal of Experimental Psychology 21 (4): 339–345.
  6. Keppel, Geoffrey, Underwood, Benton J. (1 October 1962). Proactive inhibition in short-term retention of single items. Journal of Verbal Learning and Verbal Behavior 1 (3): 153–161.
  7. Wohldmann, E.L., Healy, A.F., Bourne Jr., L.E. (2008). A mental practice superiority effect: Less retroactive interference and more transfer than physical practice. Journal of Experimental Psychology: Learning, Memory, and Cognition, 34, 823-833.
  8. Underwood, B. J. (1948). ‘spontaneous recovery’ of verbal associations. Journal of Experimental Psychology, 38, 429-439.
  9. Muller, G. E., & Pilzecker, A. (1990). Experimental contributions to memory theory. Zeitschrift fur Psychologie Eganzungsband, 1, 1-300.
  10. (1941). Retroactive and proactive inhibition in retention: evidence for a two-factor theory of retroactive inhibition. American Journal of Psychology 54: 157–173.
  11. Tulving, E., & Arbuckle, T.Y. (1966). Input and output interference in short-term associative memory. Journal of Experimental Psychology, 72, 145-150.
  12. 12.0 12.1 12.2 Roediger, H.L., III, & Schmidt, S.R. (1980). Output interference in the recall of categorized and paired associative lists. Journal of Experimental Psychology: Human Learning and Memory, 6, 91-105.
  13. 13.0 13.1 13.2 13.3 13.4 13.5 13.6 Smith, A.D. (1971). Output interference and organized recall from long-term memory. Journal of Verbal Learning and Verbal Behaviour, 10, 400-408.
  14. 14.0 14.1 14.2 Smith, A.D. (1975). Aging and Interference with Memory. Journal of Gerontology, 30, 319-325.
  15. 15.0 15.1 Marche, T.A., Howe, M.L., Lane, D.G., Owre, K.P., Briere, J.L. (2009). Invariance of Cognitive Triage in the Development of Recall in Adulthood. Memory, 17, 518-527.
  16. Baddeley, A., Eysenck, M.W. & Anderson, A.C. (2009). Memory. New York, NY: Psychology Press
  17. Brown, J. (1958). Some Test of the Decay Theory of Immediate Memory. Quarterly Journal of Experimental Psychology,10 , 12-21.
  18. Grossberg, S. (1987) The Adaptive Brain: Vision, Speech, Language and Motor Control. Amsterdam, Netherlands: Elsevier
  19. 19.0 19.1 19.2 19.3 19.4 19.5 19.6 19.7 Pashler, H. (1994). Dual Task Interference in Simple Tasks: Data and Theory. Psychological Bulletin, 116, 220-244.
  20. Navon, D & Miller, J.O. (1987). Role of outcome conflict in dual task interference. Journal of Experimental Psychology: Human Perception and Performance, 13, 438-448.
  21. 21.0 21.1 21.2 21.3 Peterson, B.S., Kane, M.J., Alexander, G.M., Lacadie, C., Skudlarski, P., Leung, H.C., Mat, J., Gore, J.C. (2002). An event-related functional MRI study comparing interference effects in the Simon and Stroop tasks. Cognitive Brain Research, 13, 427-440.
  22. Burke, Raymond., Skrull, Thomas. (1988) Competitive Interference and Consumer Memory for Advertising. Journal of Consumer Research .Vol. 15: pp. 55-68
  23. Unnava, H. Rao, Reducing Competitive Ad Interference , Journal of Marketing Research, 31:3 (1994:Aug.) p.403
  • Barnes, J.M., & Underwood, B.J. (1959). "Fate" of first-list associations in transfer theory. Journal of Experimental Psychology, 58(2), 97-105.
  • Bjork, R. A. (1992). Interference and memory. In L. R. Squire (Ed.), Encyclopedia of learning and memory (pp. 283–288). New York: Macmillan.
  • Briggs, G.E. (1954). Acquisition, extinction, and recovery functions in retroactive inhibition. Journal of Experimental Psychology, 47(5), 285-293.
  • McGeoch, J.A. (1932). Forgetting and the law of disuse. Psychological review, 39(4), 352-370.
  • Melton, A.W., & Irwin, J.M. (1940). The influence of degree of interpolated learning on retroactive inhibition and the overt transfer of specific responses. The American Journal of Psychology, LIII(2), 611-641.
  • Müller, G.E., and Pilzecker, A. (1900). Experimentelle beiträge zur lehre von gedächtnis. Zeitschrift für Psychologie 1, 1-300.
  • Salon, Heather. (2011). Dave Farrow: mind over memory. Retrieved from
  • Underwood, B.J. (1948). 'Spontaneous recovery' of verbal associations. Journal of Experimental Psychology, 38(4), 429-439.

Types of memory
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Aspects of memory
Childhood amnesia | Cryptomnesia |Cued recall | Eye-witness testimony | Memory and emotion | Forgetting |Forgetting curve | Free recall | Levels-of-processing effect | Memory consolidation |Memory decay | Memory distrust syndrome |Memory inhibition | Memory and smell | Memory for the future | Memory loss | Memory optimization | Memory trace | Mnemonic | Memory biases  | Modality effect | Tip of the tongue | Lethologica | Memory loss |Priming | Primacy effect | Reconstruction | Proactive interference | Prompting | Recency effect | Recall (learning) | Recognition (learning) | Reminiscence | Retention | Retroactive interference | Serial position effect | Serial recall | Source amnesia |
Memory theory
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Method of loci | Mnemonic room system | Mnemonic dominic system | Mnemonic learning | Mnemonic link system |Mnemonic major system | Mnemonic peg system | [[]] |[[]] |
Neuroanatomy of memory
Amygdala | Hippocampus | prefrontal cortex  | Neurobiology of working memory | Neurophysiology of memory | Rhinal cortex | Synapses |[[]] |
Neurochemistry of memory
Glutamatergic system  | of short term memory | [[]] |[[]] | [[]] | [[]] | [[]] | [[]] |[[]] |
Developmental aspects of memory
Prenatal memory | |Childhood memory | Memory and aging | [[]] | [[]] |
Memory in clinical settings
Alcohol amnestic disorder | Amnesia | Dissociative fugue | False memory syndrome | False memory | Hyperthymesia | Memory and aging | Memory disorders | Memory distrust syndrome  Repressed memory  Traumatic memory |
Retention measures
Benton | CAMPROMPT | Implicit memory testing | Indirect tests of memory | MAS | Memory tests for children | MERMER | Rey-15 | Rivermead | TOMM | Wechsler | WMT | WRAML2 |
Treating memory problems
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Prominant workers in memory|-
Baddeley | Broadbent |Ebbinghaus  | Kandel |McGaugh | Schacter  | Treisman | Tulving  |
Philosophy and historical views of memory
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Journals | Learning, Memory, and Cognition |Journal of Memory and Language |Memory |Memory and Cognition | [[]] | [[]] | [[]] |

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