QNAS QNAS QnAs with Daniel Schacter

Prashant Nair Science Writer

Since time immemorial, the fallibility of hu- was to determine whether activity in brain man has fascinated intellectuals in regions that support reactivation is associated many fields of human endeavor. In his book with subsequent true and false . The Seven Sins of Human Memory, a popular PNAS: What did you find? tome of scholarly work aimed at a general Schacter: We found that the more strongly audience, psychologist you reactivate the memory in the scanner, the Daniel Schacter, a recently elected member more likely you are—later on—to have a true of the National Academy of Sciences, de- memory of what actually happened during the scribed the vagaries of memory, including, tour. But what was especially interesting was by turns, its pixie-dust evanescence and sur- that a strong reactivation also meant that you prising persistence. Over the years, Schacter were more likely to retrieve a of has explored memory’s inherent pitfalls, such the tour later on, misremembering that an un- as its proneness to bias and misattribution, related photograph you saw in the scanner and enriched our understanding of its links was actually part of the tour. to imagination, learning, and aging. He spoke PNAS: The brain scan revealed that some to PNAS about his most recent work on the brain regions were activated during memory neural mechanisms behind the formation of reactivation. Can you elaborate? true and false memories. Schacter: Activity during scanning in brain PNAS: Youhavelongstudiedtheneural regions previously implicated in recollection— mechanisms underlying memory reactiva- retrosplenial cortex, posterior parahippocam- tion. What is memory reactivation? pal cortex, and posterior inferior parietal cor- Schacter: Memories of past experiences tex—was predictive of subsequent true and Daniel Schacter. Image by Rose Lincoln. can become reactivated in response to vari- falsememories.Totheextentthattheactiva- ous environmental cues while we are awake tion of these regions persisted when the vol- the factors that influence memory and how or asleep. We know from previous studies unteers were looking at the novel photographs to take them into account. that reactivating memories can strengthen in the scanner, they formed subsequent false PNAS: Yet the neuroscience is far from them, make them more accessible, and mod- memories of the tour. We think that this fi fl ready for routine application in courts of law. ify them with new information. Such modi- latter nding re ects the process of memory Schacter: Ourexperiment,forexample, fication is called memory updating. updating. The study also provided evidence PNAS: suggests that brain imaging might be useful In your Inaugural Article, you de- linking activity in the hippocampus with in distinguishing true and false memories, but scribe a three-step experiment with 35 volun- memory updating. it is important to emphasize that neuroimag- teers who took a self-guided audio tour of the PNAS: fi Your ndings have real world impli- ing is not yet sophisticated enough to deter- Harvard Natural History and Peabody muse- cations, such as the reliability of eyewitness mine the veracity of an individual’smemory. ums fitted with a camera that automatically testimony in courts. Most of the conclusions in basic research took pictures of stops every 15 seconds. You Schacter: Eyewitness testimony can be in- studies are based on average measures of sev- then performed functional MRI brain scans correct even when the witnesses are confident eral individuals, but in the courtroom, we as the volunteers recalled some stops on the of their testimony. People’s memory of events are usually interested in one person’smemory tour and rated the vividness of while can change when misinformation is provided of one experience. Also, laboratory studies being shown photographs of those stops in the form of, say, suggestions or misleading of true and false memories typically involve and novel photographs of exhibits they had questions. Distortions due to memory reacti- abriefdelay—minutes to days—between the not visited. Finally, you tested the volunteers’ vation might come into play when witnesses’ experience and memory testing; in the court- memorybylateraskingthemtoidentifymu- memories change in response to aspects of room, the corresponding delay may be weeks seum stops they had visited during their tour questioning. or months. Further, the possibility that mem- from a mix of target and novel photographs. PNAS: Are courts of law catching up ories might be altered through coaching adds What was the goal of the experiment? with the neuroscience underlying the fal- Schacter: Peggy St. Jacques and I had two libility of memory? another caveat to using such tests in courts. goals. The first was to determine whether the Schacter: Courts are becoming more That said, studies such as ours can inform qualityofmemoryreactivation—as measured aware of these processes. One example is jurors about how memory works; understand- by the volunteers’ subjective ratings of the re- a famous 2011 murder trial, State v. Hen- ing why memory does not work like a video lived experience while they were in the scan- derson,whichmadeitswaytotheNew recorder might lead to more informed jurors ner—improves subsequent memory for what Jersey Supreme Court and changed a long- and, thus, more informed rulings. actually happened during the tour and affects standing legal standard for evaluating

the extent to which the novel photographs pre- eyewitness evidence, eventually leading to This is a QnAs with a recently elected member of the National sented during scanning were falsely remem- tailored jury instructions—based on cogni- Academy of Sciences to accompany the member’s Inaugural Arti- bered as a part of their tour. The second tive —that inform jurors about cle, 10.1073/pnas.1319630110.

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