Short-term Memory Illusions: Study Suggests Human Memory May Be Unreliable After Just a Few Seconds

A new study by researchers at the University of Amsterdam has found that short-term memory illusions can cause people to misremember events even after a few seconds, which can be due to the brain "filling in" missing information based on expectations.

The study, published in the journal PLOS ONE, involved four experiments. Participants were presented with shapes and letters and asked to recall them after a few seconds, revealing how the brain's expectations can influence short-term memory recall.

Short-term Memory Illusions: How the Brain Fills in Missing Information Based on Expectations

The research also found that human memory may be unreliable even after just a few seconds, with scientists calling this phenomenon "short-term memory illusions." The study focused on the ability of people to recall shapes and found that they can make mistakes within just a few seconds, particularly when they have strong expectations about how the world should be.

Dr. Marte Otten, the lead author of the research, told The Guardian, "Even at the shortest term, our memory might not be fully reliable, particularly when we have strong expectations about how the world should be. When our memory starts fading a little bit - even after one and a half seconds, two seconds, three seconds - then we start filling in based on our expectations."

To investigate short-term memory illusions, the researchers conducted four experiments where participants completed basic visual memory tasks and were shown a circle of letters, some being mirror-image forms.

After a brief period, a second circle of letters was presented as a distraction before participants were asked to choose the location of a target shape and rate their confidence.

The experiments found that participants commonly selected the mirrored form of the target shape, especially when the target shape was also a mirrored letter. Participants believed they saw a real letter in more cases when it was actually a mirrored letter.

The researchers suggest that the mistakes were influenced by participants' knowledge of the alphabet and expectations rather than just the similarity in appearance. The errors increased with longer delay periods or more significant distractions but only when the target shape was a mirrored letter.

Implications of the Study's Findings for Real-world Situations and Social Expectations on Memory

The researchers note that the high confidence with which participants reported their answers rules out the possibility that the results are simply down to guessing. The findings were confirmed by results from three similar experiments involving 348 participants.

These findings have significant implications for understanding how people remember and misremember events in real-world situations. The study highlights the potential unreliability of human memory, particularly in situations where people may be more likely to depend on their expectations rather than the actual information presented to them.

The study offers important insights into the limitations of human memory and raises important questions about the reliability of eyewitness testimony in legal cases, for example. The team hopes to investigate whether similar effects hold in other types of recollection and in real-world situations.

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