Forgetting due to Interference

If simple decay through disuse cannot fully explain forgetting, an alternative and considerably more influential theory is interference theory. This theory holds that forgetting happens because of interference between different pieces of information held within the memory store, not because any of that information decays on its own. The theory assumes that learning and memorising involve forming associations between items, and that once these associations are formed, they remain intact in memory going forward — people simply keep accumulating more and more associations over time, and each of these normally sits independently, without conflicting with the others. The trouble begins at the moment of retrieval: at that point, the various sets of associations a person has formed compete with one another for retrieval, and it is this competition, not decay, that produces forgetting.

A simple exercise makes the process concrete: if a person first learns one list of nonsense syllables (List A) and then a second list (List B), and is later asked to recall List A, any items from List B that intrude into that recall attempt are there because the associations formed while learning List B are interfering with the earlier associations formed while learning List A.

Interference theory distinguishes at least two kinds of interference. Proactive interference is 'forward moving' interference: material learned earlier interferes with the recall of material learned later. Retroactive interference is 'backward moving' interference: material learned later interferes with the recall of material learned earlier. A familiar example makes the direction of each clear: if a person already knows English and finds it difficult to learn French because English keeps 'getting in the way', that is proactive interference — the earlier learning (English) is interfering with new learning (French). If, on the other hand, the same person struggles to recall English equivalents of French words precisely because they are currently busy memorising French, that is retroactive interference — the newer learning (French) is interfering with recall of the earlier learning (English). …