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Cynthia Vinney, Ph.D., is a research fellow at Fielding Graduate University's Institute for Social Innovation. She has co-authored two books on psychology and media engagement.
Updated on April 05, 2020The term interference is used to explain why people forget long-term memories. There are two forms of interference: proactive interference, in which old memories disrupt the retrieval of new memories, and retroactive interference, in which new memories disrupt the retrieval and maintenance of old memories.
Psychologists are interested in what makes us forget just as much as they are in what makes us remember. Several theories explaining why we forget have been proposed. One is interference, which suggests that an individual may fail to retrieve information from long-term memory because other information interferes. Different pieces of information in long-term memory compete, especially if that information is similar. This leads to certain information being either difficult to recall or completely forgotten.
There are many instances where you might confuse one memory with another. For example, if you go to the movies on a regular basis, you may have trouble remembering who you went to a given film with. Each time you go to the movie theater, the experience is similar. Therefore, different memories of going to the movie theater may become confused in your mind because they are so much alike.
Studies on interference date back over 100 years. One of the first was conducted by John A. Bergstrom in the 1890s. Participants sorted cards into two piles, but when the location of the second pile was changed, participants performed more slowly. This suggested that after learning the initial rules of card sorting they interfered with learning the new rules.
In the 1950s, Brenton J. Underwood examined the Ebbinghaus forgetting curve, which plots out the brain’s inability to retain information over time. He proposed that previously learned information is just as much the reason for forgetting as time is. And because we are learning all the time, there are many opportunities between when we encode information in long-term memory and when we want to retrieve that information for new memories to form that may interfere with this process.
Interference is divided into two types: proactive interference and retroactive interference.
Proactive interference happens when an individual is unable to learn new information because old information prevents its retrieval. In other words, old memories interfere with the retrieval of new memories. Older memories are often more strongly encoded in long-term memory because the individual has had more time to revisit and rehearse them. As a result, they are easier to recall than memories that were made more recently. Research has shown that one way to reduce proactive interference is to rehearse the new information through testing or recitation.
We encounter numerous examples of proactive interference in our daily lives, including:
Retroactive interference happens when an individual is unable to recall old information because new information prevents its retrieval. In other words, new memories interfere with the retrieval of old memories.
Retroactive interference has been shown to disrupt learning. In one study, participants learned a set of German-Japanese word pairs and then a different set as an interference task. The interference task was presented 0, 3, 6, or 9 minutes after the learning task. The interference task reduced learning by as much as 20% regardless of how long participants waited between being presented with the learning task and with the interference task. The researchers suggested that interference may disrupt memory consolidation.
Just like proactive interference, many cases where retroactive interference occur in our daily lives. For example:
There is a great deal of research backing up the effects of proactive and retroactive interference. However, there are some issues with the theory. Most studies on interference theory take place in a lab using word memory tasks that are presented fairly close together. In real life, people rarely perform word memory tasks, much less with only a little bit of time between them. As a result, many of the studies of proactive and retroactive interference may not be generalizable to the real world.
