Brief Exposure to Misinformation Can Lead to Long‐Term False Memories

Do false memories last? And do they last as long as true ones? This study investigated whether experimentally created false memories would persist for an extended period (one and a half years). A large number of subjects (N = 342) participated in a standard three‐stage misinformation procedure (saw the event slides, read the narrations with misinformation, and then took the memory tests). The initial tests showed that misinformation led to a significant amount of false memory. One and a half years later, the participants were tested again. About half of the misinformation false memory persisted, which was the same rate as for true memory. These results strongly suggest that brief exposure to misinformation can lead to long‐term false memory and that the strength of memory trace was similar for true and false memories. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparison of neural activity that leads to true memories,false memories,and forgetting: An fMRI study of the misinformation effect

False memories can occur when people are exposed to misinformation about a past event. Of interest here are the neural mechanisms of this type of memory failure. In the present study, participants viewed photographic vignettes of common activities during an original event phase (OEP), while we monitored their brain activity using fMRI. Later, in a misinformation phase, participants viewed sentences describing the studied photographs, some of which contained information conflicting with that depicted in the photographs. One day later, participants returned for a surprise item memory recognition test for the content of the photographs. Results showed reliable creation of false memories, in that participants reported information that had been presented in the verbal misinformation but not in the photographs. Several regions were more active during the OEP for later accurate memory than for forgetting, but they were also more active for later false memories, indicating that false memories in this paradigm are not simply caused by failure to encode the original event. There was greater activation in the ventral visual stream for subsequent true memories than for subsequent false memories, however, suggesting that differences in encoding may contribute to later susceptibility to misinformation.     

Treat and trick: A new way to increase false memory

This paper reports a new experimental manipulation that increased false memories 1 month after the manipulation. Mirroring the standard three‐stage misinformation paradigm (original event, misinformation, and test), subjects in the experimental group were first given a colour‐slide presentation of two stories (events), then given an accurate account (instead of misinformation) of the events in narrations, and finally tested for their memory of the original events. One month later, they underwent the standard misinformation paradigm with two new events. The comparison group was given the standard misinformation tasks at both time points. Results showed that the experimental group produced more false memories in the subsequent misinformation paradigm than did the comparison group. We focus on trust and credibility as possible mechanisms underlying this effect. Copyright © 2009 John Wiley & Sons, Ltd.     

Misled subjects may know more than their performance implies

Many studies have demonstrated that subjects exposed to misleading postevent information are likely to report the misinformation with confidence on subsequent tests of memory for the event. The purpose of the present studies was to determine whether subjects exposed to misleading postevent information come to believe they remember seeing the misinformation at the original event. A second question addressed by the present studies is whether exposure to misinformation reduces subjects' ability to remember the source of items they witnessed at the original event. In two experiments, subjects viewed a slide sequence depicting an event, were subsequently exposed to misleading information or neutral information about selected aspects of the event, and were later tested on their memory for the source of original and misleading details. The results showed that exposure to misinformation did not lead subjects to believe they remembered seeing the misinformation, nor did it reduce subjects' ability to accurately identify the source of originally seen details. The same pattern of results was obtained whether subjects were tested immediately (Experiment 1) or after a 1-day delay (Experiment 2). Collectively, the results suggest that subjects may report misinformation even if they know they do not remember seeing it.     

Discrepancy detection and vulnerability to misleading postevent information

When people are exposed to misleading details after a witnessed event, they often claim that they saw the misleading details as part of the event. We refer to this as themisinformation effect. In four experiments, involving 570 subjects, we explored the role that discrepancy detection plays in the misinformation effect. Experiment 1 showed that subjects who naturally read a post-event narrative more slowly were more resistant to the effects of misleading information contained in the narrative. In Experiment 2, subjects who naturally read more slowly were more likely to detect a discrepancy between what they were reading and what was stored in their memory. In Experiment 3, subjects who were instructed to read slowly were more likely to detect a discrepancy than were those who were instructed to read quickly. In Experiment 4, subjects who were instructed to read slowly were more resistant to misleading postevent information. Taken together, these results suggest that longer reading times are associated with a greater scrutiny of postevent information. This leads to an increased likelihood that discrepancies will be detected and that the misinformation will be resisted.     

Predicting confidence in flashbulb memories

Years after a shocking news event many people confidently report details of their flashbulb memories (e.g., what they were doing). People's confidence is a defining feature of their flashbulb memories, but it is not well understood. We tested a model that predicted confidence in flashbulb memories. In particular we examined whether people's social bond with the target of a news event predicts confidence. At a first session shortly after the death of Michael Jackson participants reported their sense of attachment to Michael Jackson, as well as their flashbulb memories and emotional and other reactions to Jackson's death. At a second session approximately 18 months later they reported their flashbulb memories and confidence in those memories. Results supported our proposed model. A stronger sense of attachment to Jackson was related to reports of more initial surprise, emotion, and rehearsal during the first session. Participants' bond with Michael Jackson predicted their confidence but not the consistency of their flashbulb memories 18 months later. We also examined whether participants' initial forecasts regarding the persistence of their flashbulb memories predicted the durability of their memories. Participants' initial forecasts were more strongly related to participants' subsequent confidence than to the actual consistency of their memories.     

Imagination equally influences false memories of high and low plausibility events

To examine the effects of event plausibility on people's false beliefs and memories for imagined childhood events, subjects took part in a three‐stage procedure. First, subjects rated how confident they were that they had experienced certain childhood events. They also rated their memories of the events. Second, 1 week later, subjects imagined one high, one moderate and one low plausibility event. Third, 1 week later (and 2 weeks after their initial ratings), subjects rated their confidence and memory a second time. Imagining the events made subjects more confident that they were genuine experiences and gave subjects clearer and more complete memories. Plausibility did not affect subjects' confidence but it did affect their memories. Subjects developed clearer and more complete memories for high, followed by moderate, followed by low plausibility events regardless of whether those events were imagined. We use a nested model of plausibility, belief and memory to discuss our findings. Copyright © 2008 John Wiley & Sons, Ltd.     

Sleep Increases Susceptibility to the Misinformation Effect

When individuals witness an event and are exposed to misleading postevent information, they often incorporate the misleading information into their memory for the original event, a phenomenon known as the misinformation effect. The present study examined the role of sleep in the misinformation effect. Participants (N = 177) witnessed two events; were exposed to misleading postevent information immediately, 12 hours later the same day, 12 hours later the next day, or 24 hours later; and then took a recognition test. All groups demonstrated the misinformation effect, and this effect was larger in groups with an overnight retention interval. Signal detection analyses revealed that sleep decreased sensitivity. These results suggest that sleep increases susceptibility to the misinformation effect, which may occur because sleep results in gist‐based representations of original events or because sleep improves learning of postevent information. Implications for interviewing eyewitnesses are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

The eyewitness suggestibility effect and memory for source

We examined the possibility that eyewitness suggestibility reflects failures of the processes by which people normally discriminate between memories derived from different sources. To test this hypothesis, misled and control subjects were tested either with a yes/no recognition test or with a "source monitoring" test designed to orient subjects to attend to information about the sources of their memories. The results demonstrate that suggestibility effects obtained with a recognition test can be eliminated by orienting subjects toward thinking about the sources of their memories while taking the test. Our findings indicate that although misled subjects are capable of identifying the source of their memories of misleading suggestions, they nonetheless sometimes misidentify them as memories derived from the original event. The extent to which such errors reflect genuine memory confusions (produced, for example, by lax judgment criteria) or conscious misattributions (perhaps due to demand characteristics) remains to be specified.     

Combating Co‐witness contamination: Attempting to decrease the negative effects of discussion on eyewitness memory

Witnesses who discuss an event with others often incorporate misinformation encountered during the discussion into their memory of the event. Two experiments were conducted to establish whether this memory conformity also occurs in the context of an interview and whether it is possible to reduce the effect. Participants viewed a crime‐video which they then discussed with a co‐witness. Some participants were warned they may have been exposed to misinformation during the discussion before all were interviewed individually. In Experiment 1, participants made remember/know judgments about each component of their free recall, and in Experiment 2 they were asked to indicate the source of their memories. Co‐witness information was incorporated into participants' testimony, and this effect could not be significantly reduced using warnings and source‐monitoring instructions. Remember/know judgments may be useful in distinguishing ‘real’ memories from false memories. We make some recommendations regarding the interviewing of witnesses. Copyright © 2009 John Wiley & Sons, Ltd.     

Is saccade-induced retrieval enhancement a potential means of improving eyewitness evidence?

Saccade-induced retrieval enhancement (SIRE) is the effect whereby making bilateral saccades enhances the subsequent retrieval of memories. Two experiments explored SIRE's potential to improve eyewitness evidence. Participants viewed slideshows depicting crimes, and received contradictory and additive misinformation about event details either once (Experiment 1) or three times (Experiment 2). Participants then performed saccades or a fixation control task before being tested on their memory for the slideshows and making confidence judgements. Saccades increased discrimination between seen and unseen event details regardless of whether or what type of misinformation was presented. Because prior studies indicated that SIRE might be more robust for individuals who are strongly right-handed versus not, we examined SIRE as a function of handedness and found that saccades improved memory for event details regardless of participants' handedness. However, participants who were not strongly right-handed had fewer false memories than participants who were strongly right-handed, extending previous findings of superior memory among individuals who are not strongly right-handed. Saccades also increased confidence in true memories (Experiment 1) and decreased confidence in false memories (Experiment 2). The results support SIRE's potential to improve eyewitness evidence.     

The quality of suggested memories

Alarge number of studies have demonstrated that participants could be led to report suggested events that were never witnessed (Loftus & Palmer, 1974 ). The present study attempts to explore the quality of such suggested memories. Thirty‐six participants were exposed to a live event of brief duration (20 s). They were then misled about certain aspects of the event. Memory was assessed using a forced‐choice recognition test. The participants were also required to give remember/know/guess responses, together with confidence ratings, and also to indicate how they came to remember the item. Thirty‐six per cent of the suggested memories were “know” responses, while 43% were “remember” responses. Moreover, whenever the participants had a remember experience they always recalled a wealth of visual information. With regards to the confidence level of the suggested memories, it was observed that the suggested memories were as confidently held as accurate memories. The results indicate that suggestions may become integrated with other kinds of information and that these falsely remembered memories are often accompanied with varied kinds of information; predominant among them seems to be visual imagery and past associations. For accurate memories, too, visual imagery was recalled the most, followed by other kinds of information (e.g., past associations, emotional, auditory, and inferential). The study points to the difficulties of differentiating between true recollections of actual events and false recollections of events that did not occur.     

Misinformation revisited: New evidence on the suggestibility of memory

In three experiments involving a total of 623 subjects, a series of slides was shown depicting a student in a college bookstore stealing a variety of items. Next, subjects read a narrative describing the event that contained some misinformation and some neutral information about several critical details. Finally, subjects took a memory test. On this test, subjects were asked to list exemplars of 20 specified categories but were instructed not to list any items that they saw in the slide sequence. Analogous to Lindsay's (1990) adaptation of Jacoby, Woloshyn, and Kelley's (1989) “logic-ofopposition” paradigm, the tendency to report suggested details was thus set in opposition to the ability to remember the source of those details. Therefore, we interpreted failure to include suggested details as exemplars as evidence that subjects believed those details had been present in the event. Analysis of subjects' responses under opposition instructions suggests that some misled subjects come to genuinely believe that they saw items that, in reality, were only suggested to them.     

Effects of Social-Comparative Memory Feedback on Eyewitnesses' Identification Confidence,Suggestibility, and Retrospective Memory Reports

In 2 experiments, college students watched a videotaped theft and either recounted it orally or completed an objective memory test about it. Later, some eyewitnesses received either positive or negative feedback about these memory reports, suggesting a cowitness's report agreed or disagreed with theirs or that they had better or worse memory accuracy than most cowitnesses. Feedback influenced a number of subsequent memory-related responses. Witnesses who had received positive (vs. no) memory feedback later evinced heightened suggestibility in terms of accepting misinformation embedded in a memory interview and made identifications more confidently, quickly, and (in one condition) accurately. Witnesses who had received negative memory feedback evinced heightened suggestibility, made identifications less confidently, and recalled the witnessing and identification experience as involving poorer conditions for memory. Feedback appears to influence the overall self-credibility of memory, thereby altering confidence in both the feedback-specific memory and other aspects of memory for the event.     

Post‐event information presented in a question form eliminates the misinformation effect

This study investigated the influences of sentence surface forms on the misinformation effect. After viewing a film clip, participants received a post‐event narrative describing the events in the film. Critical sentences in the post‐event narrative, presented in either a statement or a question form, contained misinformation instead of questions with embedded false presuppositions; thus participants did not have to answer questions about the original event. During the final cued‐recall test, participants were informed that any relevant information presented in the post‐event narrative was not in the original event and that they should not report it. Consistent with previous findings, Experiment 1 demonstrated that post‐event information presented as an affirmative statement produced the misinformation effect. More importantly, post‐event information presented in a question form, regardless of whether it contained a misleading or studied item, increased the recall of correct information and reduced false recall. Experiment 2 replicated the main finding and ruled out an alternative explanation based on the salience of misleading items. Post‐event information presented in a question form created a condition similar to that which produces the testing effect.     

Neural activity during encoding predicts false memories created by misinformation

False memories are often demonstrated using the misinformation paradigm, in which a person's recollection of a witnessed event is altered after exposure to misinformation about the event. The neural basis of this phenomenon, however, remains unknown. We used fMRI to investigate encoding processes during the viewing of an event and misinformation to see whether neural activity during either encoding phase could predict what would be remembered. fMRI data were collected as participants studied eight vignettes (Original Event phase). Shortly afterward, participants studied the same vignettes during scanning, but with changes to several details, serving as the misinformation (Misinformation phase). Two days later, their memories for the Original Event were assessed. Activity that subsequently led to true and false memories was examined during both encoding phases. Two interaction patterns between encoding phase (Original Event and Misinformation) and type of memory (true and false) were observed in MTL and PFC regions. In the left hippocampus tail and perirhinal cortex, a predictive item-encoding pattern was observed. During the Original Event phase, activity was greater for true than false memories, whereas during the Misinformation phase, activity was greater for false than true memories. In other regions, a pattern suggestive of source encoding was observed, in which activity for false memories was greater during the Original Event phase than the Misinformation phase. Together, these results suggest that encoding processes play a critical role in determining true and false memory outcome in misinformation paradigms.     

Testing potentiates new learning in the misinformation paradigm

Retrieval enhanced suggestibility (RES) is the finding that the misinformation effect is exacerbated when a test precedes misleading postevent information (Chan, Thomas, & Bulevich Psychological Science 20: 66–73, 2009). In the present study, we tested three hypotheses relevant to RES. First, we examined whether retrieval of critical details was necessary for the RES effect. Second, we examined whether initial testing influenced the allocation of attention to critical details during postevent information processing. Finally, we examined whether RES resulted in impaired access to the originally learned information. We compared three groups of participants in three experiments: an identical-test group, a related-test group, and a standard misinformation group. Both testing groups were tested on the original event before the introduction of misinformation; however, the identical-test group took the same test before and after the misinformation, whereas the related-test group took different tests before and after misinformation. We found that testing before misleading postevent information affected attention allocation to details in the postevent narrative. Furthermore, the RES effect did not accompany reduced accessibility to the original information, as measured by a modified–modified free recall test. These data have implications for how testing may potentiate new learning.     

Misinformation and memory: the creation of new memories

Misleading information presented after an event can lead people to erroneous reports of that misinformation. Different process histories can be responsible for the same erroneous report in different people. We argue that the relative proportion of times that the different process histories are responsible for erroneous reporting will depend on the conditions of acquisition, retention, and retrieval of information. Given the conditions typical of most misinformation experiments, it appears that misinformation acceptance plays a major role, memory impairment plays some role, and pure guessing plays little or no role. Moreover, we argue that misinformation acceptance has not received the appreciation that it deserves as a phenomenon worthy of our sustained investigation. It may not tell us anything about impairment of memories, but it does tell us something about the creation of new memories.     

Memory impairment in the weapon focus effect

Two experiments are reported in which postevent source of misinformation was manipulated within weaponpresent and weapon-absent scenarios. Participants viewed slides depicting either a weapon or a newspaper event and then received either incomplete questioning or a narrative. Both postevent sources contained misleading information about a central and peripheral detail concerning either the weapon or the newspaper scenario. With a modified test in Experiment 1, questioning was found to increase misinformation effects concerning the central item, as compared with a narrative, and more misinformation effects were found for the weapon-peripheral than for the newspaper-peripheral item. In Experiment 2, the participants were more likely to claim to have seen contradictory and additive misinformation about the central item in the slides following questioning, and more contradictory and additive misinformation effects occurred for the weapon-peripheral than for the newspaper-peripheral item. The findings are considered in terms of the effects of both postevent and encoding factors on memory.     

Undoing suggestive influence on memory: The reversibility of the eyewitness misinformation effect

Presenting inconsistent postevent information about a witnessed incident typically decreases the accuracy of memory reports concerning that event (the misinformation effect). Surprisingly, the reversibility of the effect (after an initial occurrence) has remained largely unexplored. Based on a memory conversion theoretical framework and associated refined assessment strategy, we report three experiments to demonstrate that suggestive influence can be completely undone. Initially established misinformation effects were eliminated - even after a period of 5weeks (Exp. 3) - through (a) an enlightenment procedure ensuring an adequate representation of the memory task as a search for potentially two contradictory items (instead of "the" single "correct" answer) and (b) using a memory state test that unconfounds the performance contributions of item and source memory by assessing them separately. Specifically, memory for original event details that were the target of misinformation was restored to the level of non-misled control performance, and even beyond (Exp. 3). This remarkable reversibility of misinformation influence highlights the central role of memory conversion processes in the misinformation effect (but does not principally exclude the contribution of traditional interference processes). We discuss the compatibility of our findings with previous research and make suggestions for real-world eyewitness interrogation.