Remember the telephone game where people take turns whispering a message into the ear of the next person in line? By the time the last person speaks it out loud, the message has radically changed. It’s been altered with each retelling.

Turns out your memory is a lot like the telephone game, according to a new Northwestern Medicine study.   Every time you remember an event from the past, your brain networks change in ways that can alter the later recall of the event. Thus, the next time you remember it, you might recall not the original event, but what you remembered the previous time. The Northwestern study is the first to show this.

“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 Donna Bridge, a postdoctoral fellow at Northwestern University Feinberg School of Medicine and lead author of the paper on the study recently 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.”

The findings have implications for witnesses giving testimony in criminal trials, Bridge noted.  “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.”

The published study reports on Bridge’s work with 12 participants, but she has run several variations of the study with a total of 70 people.

“Every single person has shown this effect,” she said. “It’s really huge," said Bridge.   The reason for the distortion, Bridge said, is the fact that human memories are always adapting.

“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.”

For the study, people were asked to recall the location of objects on a grid in three sessions over three consecutive days.  “Our findings show that incorrect recollection of the object’s location on day two influenced how people remembered the object’s location on day three,” Bridge explained. “Retrieving the memory didn’t simply reinforce the original association. Rather, it altered memory storage to reinforce the location that was recalled at session two.”

“This study shows how memories normally change over time, sometimes becoming distorted,” Bridge noted. “When you think back to an event that happened to you long ago -- say your first day at school -- you actually may be recalling information you retrieved about that event at some later time, not the original event.”

Author:   Marla Paul, Northwestern NewsCenter

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