Memories can Change just by Trying to Remember them

     In 2012, Dr. Donna Bridge and Dr. Ken Paller published the beginnings of their research into the causes, correlations, and effects of memory retrieval on memory consolidation and memory distortion. In their paper, entitled Neural Correlates of Reactivation and Retrieval-Induced Distortion, the researchers hypothesized that "retrieval preferentially promotes storage of retrieved information instead of merely strengthening memory for the original event" (Bridge & Paller).

     But first, let's take it back a notch. What is retrieval? Retrieval, or the recall, or memory refers to the act of re-accessing previously stored information in the brain. In common terms, it is the act of remembering. During retrieval, the brain replays the pattern of neural activity that was originally occurring with and is now associated to the memory being retrieved, basically mimicking the brain's perception of the real event. Interestingly, this suggests a lack of strong distinction between the act of thinking and the act of remembering.

     Memory reactivation is the term for the re-visiting of those neural networks that were formed during the encoding of the original information. Retrieval is thought to be able to alter memory storage through some reactivation-related mechanism. This is because during retrieval, "environmental information in the current spatiotemporal context could become associated with stored information" (Bridge & Paller). In other words, memory could come to include not just information from the original context during which it was initially encoded, but also information (erroneous information) from the retrieval event. You can think of memory as not being frozen in time, and the act of remembering actually being an act of creatively re-imagining.

     This act of incorporating new information into a memory can lead to scenarios of memory distortion, or even entirely false memories, which leads us back to the original hypothesis of this study. A consequence of retrieval preferentially promoting storage instead of merely consolidating and strengthening the original memory is that information that's different from the original memory will become part of that memory, leading to distortion. Bridge & Paller tested this by testing object-location associations over 3 sessions. In session 1, participants learned object-location associations. In session 2, participants were shown only a subset of the objects from session 1, but with different locations than from session 1. In session 3, participants were asked to recall all the object-location associations.

     They found that participants in session 3 placed objects closer to their associated locations in session 2 than in session 1. The degree to which objects were placed closer to session 2 locations than to session 1 locations provided a measure of retrieval-induced distortion. Electroencephalogram (EEG) analyses corroborated the cued recall test results with readings that showed neural distinctions between accurate recall during time of retrieval and inaccurate future recall through incorporation of erroneous new information.

Retrieval bias contrasts with memory accuracy. T3 locations were much closer to T2 locations (retrieval bias) than to T1 locations (memory accuracy).

     The implications of these results are not lost in the legal profession. Elizabeth Loftus is a world-renowned cognitive psychologist who has studied the malleability of human memory. Her groundbreaking research on the misinformation effect, the lack of reliability in eyewitness testimony, and the creation of false memories has been incorporated into legal defense arguments countless times. In her study, Reconstruction of Automobile Destruction: An Example of the Interaction between Language and Memory, she shows how simply the wording of a question about a memory can dramatically influence the recreation of that memory, even permanently changing those memories for future recall. Her results led her to develop the misinformation paradigm, which demonstrated that eyewitness memories are altered after exposure to incorrect information. Her student, Jim Coan, developed the famous "lost in the mall" technique, a memory implantation technique designed to show that confabulations about events that never happened can be created through suggestion.

     The importance of this work is most significant in our legal system. Some of the most notable cases Dr. Loftus has worked with due to her discoveries regarding the malleability of memory, include the trials of O. J. Simpson, mass murderers Ted Bundy, Kenneth Bianchi, and Angelo Buono, the officers in the Rodney King beating, and litigation involving Michael Jackson and Martha Stewart. Loftus' work has resulted in stricter requirements for the use of recovered memories in trials, as well as a greater requirement for corroborating evidence. In addition, some states no longer allow prosecution based on recovered memory testimony.

     Dr. Bridge's and Dr. Paller's research is significantly important because it's the first time discovering concrete neural correlates to retrieval-induced distortions.

References

Bridge, D. J., & Paller, K. A. (2012). Neural Correlates of Reactivation and Retrieval-Induced Distortion. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 32(35), 12144–12151.

Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13(5), 585–589.

Image from Bridge & Paller (2012).