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.Edwards, W. H. (2010). Motor Learning and Control: From Theory to Practice. Belmont, CA: Cengage Learning. There is an immense number of encoded memories within the storage of LTM. The challenge for memory retrieval is recalling the specific memory and working in the temporary workspace provided in STM. Retaining information regarding the relevant time of encoding memories into LTM influences interference strength. There are two types of interference effects: proactive and retroactive interference.
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. 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.
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.Underwood, B. J. (1957). Interference and forgetting. Psychological Review, 64(1), 49.
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. The United States again made headway in 1932 with John A. McGeoch suggesting that decay theory should be replaced by an interference theory. 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.
Proactive interference Proactive interference is the interference of older memories with the retrieval of newer memories. Of the two effects of interference theory, proactive interference is the less common and less problematic type of interference compared to retroactive interference. Previously, it had been hypothesized that forgetting working memories would be nonexistent if not for proactive interference.
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. 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. If the items or pairs to be learned are conceptually related to one another, then proactive interference has a greater effect. 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. 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.
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. 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.
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. Proactive interference also affected learning when dealing with multiple lists. Researchers had participants learn a list of ten paired adjectives. 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. 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. Proactive Interference affects susceptibility to span performance limitations, as span performance in later experimental trials were worse than performance in earlier trials. 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.
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. 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. 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. Of the two effects of interference theory, retroactive interference is considered the more common and more problematic type of interference compared to proactive interference.
RI is a classic paradigm that was first officially termed by Muller. 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.
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".
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.
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. 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. 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. 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. 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.
Theories