Tags: memories | change | retell

Study: Memories Change With Retellings

Monday, 24 Sep 2012 01:07 PM


In findings with significant implications for witness testimony in criminal trials, scientists have determined a person’s memories may change with each recounting of a past event.
A new study by Northwestern University researchers suggests every time a person remembers an event from the past, the brain networks change in ways that can alter the later recall of the event – such that he or she may not be remembering details of the actual incident itself, but the previous memory of it.
Lead researcher Donna Bridge, a postdoctoral fellow at Northwestern’s Feinberg School of Medicine, said the study found memory is like the “telephone game,” where people take turns whispering a message into the ear of the next person in a group – typically altering it with each retelling such that the last version is radically different from the first.
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"A memory is not simply an image produced by time traveling back to the original event – it can be an image that is somewhat distorted because of the prior times you remembered it," said Bridge, whose findings were published in the Journal of Neuroscience. "Your memory of an event can grow less precise even to the point of being totally false with each retrieval."
She said the findings may explain why trial witnesses may give differing accounts of the same event at various times during testimony.
"Maybe a witness remembers something fairly accurately the first time because his memories aren't that distorted," she said. "After that it keeps going downhill."
Bridge said she was able to demonstrate the phenomenon in tests involving 70 people who were asked to recall the location of objects on a grid in three sessions over three days. On the first day, participants learned a series of 180 unique object-location associations on a computer screen. The next day, they were given a recall test in which they viewed a subset of those on the grid and were asked to move them to their original location. Then on the last day, participants returned for a final recall test.
The results showed improved recall accuracy on the final test for objects that were tested on day two, but they tended to place the objects closer to the incorrect location from the second day, rather than the original location from day one.
Bridge's findings also were supported when she measured the electrical activity of the brains of participants when they tried to recall the object locations – indicating new memories are being made during periods of recall.
The reason for the distortion, Bridge said, is the fact that human memories are always adapting.
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"Memories aren't static," she noted. "If you remember something in the context of a new environment and time, or if you are even in a different mood, your memories might integrate the new information."
As a result, she added: "When someone tells me they are sure they remember exactly the way something happened, I just laugh."
The research was funded, in part, by the National Science Foundation and National Institute of Neurological Disorders and Stroke of the National Institutes of Health.



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Scientists have determined a person’s memories may change with each recounting of a past event.
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2012-07-24
Monday, 24 Sep 2012 01:07 PM
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