How can we remember events from 10 years ago but easily forget what we learned a day ago? And what happens to the forgotten memories anyway? Do they disappear? According to the interference theory of Forgetting, sometimes other similar events obstruct our access to memories. Even though these memories are still there, we can't recall them. In this article, we'll see how interference has been studied in psychology.
- We'll begin by looking at the interference Psychology definition.
- Next, we'll look at proactive and retroactive interference examples.
Then, we'll describe McGeoch and McDonald’s (1931) classical study on interference.
Moving on, we'll focus on contemporary studies on interference theory psychology.
We'll use research to demonstrate how retroactive interference psychology and proactive interference psychology affect Forgetting.
Interference Psychology: Definition
Interference is an explanation for Long-Term Memory forgetting. According to this theory, memories similar to the target Memory can hinder retrieval.
Interference is a process that affects Memory recall in which specific memories interfere with the retrieval of other memories.
Interference occurs when we can't access the target Memory because other similar memories make it difficult to do so.
This is because we often rely on cues associated with a memory to recall it. When multiple similar memories are associated with the same cue, retrieval will be impaired.
Proactive and Retroactive Interference Examples
There are two types of interference: proactive and retroactive interference.
Proactive interference occurs when old memories interfere with recalling a new memory.
Let's say that you're learning German and Dutch. Last week you learnt Dutch words for different animals and this week you're studying German names. You might find that when you try to recall German names, the only thing that comes to mind is the Dutch ones.
Here the old memory (Dutch names) are interfering with the retrieval of new memories (German names). This is likely because they are both associated with similar cues.
On the other hand, retroactive interference occurs when the new memories interfere with what you have learnt earlier.
For example, you forgot what you learnt in your morning biology class after studying similar concepts in chemistry right after.
It might be challenging to remember which type of interference is which. Remember that the word retro means backwards, while pro means forward.
- Retroactive interference can be associated with moving backwards on a timeline of memories (new affects old).
- While proactive interference can be associated with a movement forward on this timeline (old affect new).
Contemporary Studies on Interference Theory in Psychology
One of the early studies that aimed to investigate the effect of retroactive interference was conducted by McGeoch & McDonald (1931).
Studies on Interference: McGeoch and McDonald’s (1931) Classical Study
In this study, participants were asked to remember a list of words until they could recall it perfectly. Then, participants had to learn a new, second list. There were six groups, and each learned a different set of words for the second list.
You can see the groups listed in the table below:
| Group 1 | Synonyms – words with the same meaning as the originals |
| Group 2 | Antonyms – words with the opposite meanings as the originals |
| Group 3 | Words unrelated to the original words |
| Group 4 | Nonsense syllables |
| Group 5 | Three-digit numbers |
| Group 6 | No new list – these participants just rested (Control Condition) |
Participants then had to recall the original list of words.
Group 1, who learned the list with the most similar material (synonyms), had the worst recall. Group 5, who learned the most irrelevant material (numbers), had the best recall, apart from the control group.
It was concluded that the more similar information is, the more likely it will interfere retroactively with older memories.
Now, let's look at some more recent studies on proactive and retroactive interference.
Retroactive Interference in Psychology
Sosic-Vasic et al. (2018) studied whether the timing at which the new information is learnt will affect the degree of retroactive interference. Their sample consisted of 30 high school students, who were given a list of 12 German-Japanese word pairs and then another list right after, 3, 6 or 9 minutes after the first list. There was also a control condition when no second list was presented. Then, participants were asked to recall the information from the first list.
The study design was within participants, meaning that each participant took part in each condition, with 2-day breaks between them. They also went through the conditions in different orders to prevent order effects.
The researchers found that:
- When participants were presented with the second list (no matter the time), the memory performance on the first list dropped by 20%.
- The time at which the second list was presented affected different students differently.
It was concluded that the period of 12 minutes after learning information is crucial for memory consolidation, and introducing similar information during this time results in retroactive interference.
Fig. 1 - Retroactive interference can make memorising a lot of similar information in a brief period of time ineffective.
Proactive Interference in Psychology
Contemporary research on proactive interference has identified that it occurs when memories rely on the same neural circuit. It has also been found that a mnemonic technique called the Method of Loci can reduce Proactive Interference.
Studies on Interference: Crossley et al. (2019): What Leads to Proactive Interference?
Crossley et al. (2019) investigate the time during which memories are sensitive to interference and the role of shared neural circuits between the target and interfering memories. They used conditioning to teach a pond snail to associate a stimulus with a reward (appetitive learning) or punishment (aversive learning).
Appetitive and aversive learning engages different neural circuits in the snail.
The authors investigated what would happen if new learning occurred when the old memory was still fresh and vulnerable to disruptions and what would happen if the old memory was already stable.
When the snail was taught a new association, no matter if it was similar to the first one, when the first memory was still vulnerable, the old one was forgotten due to retroactive interference.
- When the old memory was already stable, and new information was introduced, proactive interference occurred, but only if the new memory engaged the same neural circuit (e.g. both new and old ones were appetitive). When the new memory engaged a different circuit (it was aversive), no interference occurred.
| Type of new memory introduced |
| Similar to the old one (appetitive) | Different to the old one (aversive) |
| Time from learning the old memory | Short: Old memory is still vulnerable | Retroactive interference (old memory forgotten) | Retroactive interference (old memory forgotten) |
| Long: Old memory is stable | Proactive interference (new memory forgotten) | No interference (both memories preserved) |
This study shows that in the case of retroactive interference, the time might be more important than shared neural circuits. Even if the new memory doesn't involve the same cues, it can still interfere with the old one.
While proactive interference only occurs if both memories engage the same circuits and can occur even after the new memory has become stable.
Studies on Interference: Bass & Oswald (2014) Overcoming Proactive Interference
The famous Sherlock Holmes often talks about using a mnemonic technique called the mind palace to remember a large amount of complex information. This technique is also called the Method of Loci, and it involves associating each new piece of information you learn with an object that is part of a space you are familiar with (e.g. your house).
By systematically associating each piece of information with a different object, you can later use the mental image of the space to recall the information in the correct order.
Bass & Oswald (2014) aimed to investigate whether the Method of Loci mnemonic can be an effective way to prevent proactive interference.
They divided 94 undergraduate participants into two groups. Both groups were asked to memorise five lists, each containing five words in the fruit category. One group was trained on how to use the Method of Loci to memorise the lists, while the other was just told to memorise the list.
The group that was trained on the Method of Loci technique was asked to choose five places (e.g. five adjoining rooms) that they are familiar with and associate the words from the lists with objects in the rooms. Each list was to be associated with one room. Each word on the list was to be associated with a different object in that room.
Then the participants were asked to recall as many words from the lists as they could remember in any order.
The study found that:
- The group who wasn't taught the mnemonic had a 38% reduction in recall of words across lists due to proactive interference.
- In contrast, the group taught the Method of Loci technique showed a significant reduction in proactive interference, with only a 25% reduction in recall across lists.
This shows that associating the information with separate cues can help us prevent proactive interference. Keep this technique in mind next time you're memorising a list!
Fig. 2 - The Method of Loci mnemonic uses the representations of spaces which are familiar to you to prevent proactive interference.
Studies on Interference - Key takeaways
- Interference is an explanation for Long-Term Memory forgetting. According to this theory, memories that are similar to the target memory, the one we are trying to recall, hinder its retrieval.
- Proactive interference occurs when old memories interfere with recalling a new memory.
- Retroactive interference occurs when new memories interfere with what you have learnt earlier.
- McGeoch & McDonald (1931) showed that learning new information can interfere with past similar memories.
- Sosic-Vasic et al. (2018) highlight that when new information is presented at a time when the old memory has not yet been consolidated, retroactive interference occurs (the old memory is forgotten).
- Crossley et al. (2019) highlight the role of shared neural circuits in proactive interference and time in retroactive interference.
- Bass & Oswald (2014) propose that proactive interference can be prevented by using the Method of Loci mnemonic, which associates each piece of information with a different object in a space that is familiar to you.
References
- McGeoch, & McDonald, W. T. (1931). Meaningful Relation and Retroactive Inhibition. The American Journal of Psychology, 43(4), 579–588. https://doi.org/10.2307/1415159
- Sosic-Vasic, Hille, K., Kröner, J., Spitzer, M., & Kornmeier, J. (2018). When Learning Disturbs Memory - Temporal Profile of Retroactive Interference of Learning on Memory Formation. Frontiers in Psychology, 9, 82–82. https://doi.org/10.3389/fpsyg.2018.00082
- Crossley, M., Lorenzetti, F.D., Naskar, S. et al. Proactive and retroactive interference with associative memory consolidation in the snail Lymnaea is time and circuit dependent. Commun Biol 2, 242 (2019). https://doi.org/10.1038/s42003-019-0470-y
- Bass, W. S., & Oswald, K. M. (2014). Proactive control of proactive interference using the method of loci. Advances in cognitive psychology, 10(2), 49–58. https://doi.org/10.5709/acp-0156-3
Explanations 
Textbooks 
Exams 
Magazine 
