Forgetting is a memory problem that plagues us all. Little wonder then why researchers have devoted so much time and energy to understanding why we forget and the cognitive process behind memory failures. Researchers have explored a number of different theories and explanations for why people forget things. Sometimes the information is never properly stored in memory in the first place. Sometimes the memory of an event or piece of information simply fades with time.
But one of the most common reasons for forgetting might surprise you
According to one recent study, sometimes the act of recalling some memories actually causes other memories to be forgotten.
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Study Looks at the Adaptive Mechanism for Forgetting
In the study published in the journal Nature Neuroscience, researchers from the University of Birmingham and the MRC Cognition and Brain Sciences unit in Cambridge utilized brain images to look at the adaptive mechanism for forgetting in the human brain. The result revealed how certain cortical patterns that underlie competing memories are suppressed. While there have been earlier studies on how memories interfere with one another, the researchers suggest that this is the first to look at the actual mechanisms for forgetting.
“Though there has been an emerging belief within the academic field that the brain has this inhibitory mechanism, I think a lot of people are surprised to hear that recalling memories has this darker side of making us forget others by actually suppressing them,” explained Dr. Maria Wimber of the University of Birmingham in a statement.
This adaptive forgetting strengthens the more frequently recalled memories while weakening competing memories. When memories are not reinforced through recall, they become weaker and weaker and may even be forgotten entirely.
The study involved using MRI scans to monitor brain activity in participants who were asked to recall memories of images they had been shown earlier. The participants were asked to repeatedly recall memories of target images, and naturally these memories became more vivid each time they were recalled. What the researchers found, however, was that competing memories became much more difficult to remember.
Forgetting Isn’t Just a Passive Process
“People are used to thinking of forgetting as something passive. Our research reveals that people are more engaged than they realize in shaping what they remember of their lives. The idea that the very act of remembering can cause forgetting is surprising, and could tell us more about selective memory and even self-deception,” said Dr. Anderson of the MRC Cognition and Brain Science unit in a press release.
The study’s results also have important real-world implications, particularly in the area of eye-witness testimony, the researchers suggested. Since witnesses are often asked to recall and repeat the same, specific memory over and over again, this constant recall might seriously impair associated, competing memories. This might create the impression that the witness’s memory of the event is poor, when really it is the repeated recall leading to the forgetting of important details.
It’s important to note that the results of the study do not mean that as you put one thing into your memory, another thing is pushed out. When you study algebra, everything you learned in your chemistry class doesn’t get dumped from you memory banks. Instead, the repeated recall of certain memories signals to the brain that that information must be really important. By elevating that information in status, the brain wants to be sure that you have access to it when you need it. For that reason, the connections related to that memory become strengthened, while the networks that compete with that memory weaken.
While this interference mechanisms can obviously cause problems with remembering, Wimber suggests that it might just have a bright side.
“Forgetting is often viewed as a negative thing, but of course, it can be incredibly useful when trying to overcome a negative memory from our past. So there are opportunities for this to be applied in areas to really help people,” she suggested.
University of Birmingham. (2015, March 16). New images of the brain show the forgetful side of frequent recall. EurekAlert. Retrieved from http://www.eurekalert.org/pub_releases/2015-03/uob-nio031115.php
Wimber, M., Alink, A., Charest, I., Kriegeskorte, N., & Anderson, M. C. (2015). Retrieval induces adaptive forgetting of competing memories via cortical pattern suppression. Nature Neuroscience. doi:10.1038/nn.3973