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Interference theory

Interference theory refers to the idea that forgetting occurs because the recall of certain items interferes with the recall of other items. In nature, the interfering items are said to originate from an overstimulating environment.

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 second intervals, ( 3. 6. 9 etc..) 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.

Additional recommended knowledge



According to the theory there are three kinds of interference: proactive interference, retroactive interference and output interference.But more emphasis is placed on proactive and retroactive which often happens in our everyday life and dealings.

Proactive interference

Proactive Inhibition is a psychological concept that describes the increased difficulty learning or remembering a set of words after that set had been learned in a previous, different context. It applies to free recall and associative or list learning procedures of assessing memory. One explanation based on the notion of interference suggests that learning a new set of associations is made more difficult because the old associations continue to intrude in memory. A slightly different perspective, suggests that the earlier learning distracts a learner from rehearsing the new list of words to be remembered, and so learning is reduced. A different view suggest that the problem is not in learning the second, redundant list, but occurs only at the time of recall of the second list when retrieval cues overlap and recall is reduced. When new information is harder to remember or easier to forget as it is confused with old information.

Retroactive interference

Retroactive interference occurs when later learning interferes with previous learning. When the processing of new information interferes with old information

Output interference

Output interference occurs when the "activity of retrieving, ITSELF", interferes with the retrieval of the actual information needed in the first place. Primarily, this is caused by the limited capacity of the short-term memory.

However, the above which is proactive and retroactive has been widely been researched and proved to be the main types of interference in psychology.


Sternberg, Robert J. (2006). Cognitive psychology fourth edition. Thomson Wadsworth, 219. ISBN 0534514219.

See also

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Interference_theory". A list of authors is available in Wikipedia.
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