Output monitoring tests reveal false memories of memories that never existed

Three experiments were conducted to assess participants' beliefs about potential false memories that might have occurred during free recall tests. An input-output monitoring test was administered that required participants to discriminate between items that were studied and recalled, studied and not recalled, or were entirely new. Critical lures from Roediger and McDermott's (1995) paradigm were inserted into this test. The results demonstrated that participants believed erroneously recalled items were both studied and recalled. The intriguing finding was that unrecalled items were believed to have been studied approximately 80% of the time, and half of those were also believed to have been recalled. This result represents a dual false memory effect in which items were believed to have been studied and also to have been recalled. The ramifications of this new procedure are discussed in terms of proposed experiments that might clarify the genesis of these false memories.     

Correcting socially introduced false memories: The effect of re-study

This study examined whether participants could utilize re-study and perceptual elaboration to correct erroneous suggestions from their partner in the social contagion of memory paradigm. Participants studied household scenes and then collaboratively recalled the scenes with a confederate who interjected erroneous items. Before completing subsequent individual recall and recognition tests, participants were allowed to re-study the original items and/or to generate perceptual details of the items. Across two experiments, participants who re-studied the original material were less likely to incorporate the confederate's misleading suggestions. Re-study reduced false recall and recognition and increased veridical recall and recognition (Experiment 1) and the effect was especially pronounced with longer re-study episodes (Experiment 2). Items generated on the perceptual elaboration test offered no corrective benefit above and beyond the effects of re-study. These data demonstrate that participants can rely on self-initiated correction processes engaged during re-study to reduce socially suggested false memories.     

Assessing the effectiveness of warnings and the phenomenological characteristics of false memories

The phenomenology of false memories was investigated in three experiments in which participants heard two experimenters read lists of items that were related to critical nonpresented items. In Experiments 1, following a recognition memory test, participants rated the phenomenological characteristics of their memories immediately and after a 48-hour delay. False recognition was prevalent and on several dimensions participants rated their true memories as more vivid than their false memories. In Experiments 2 and 3, following the study phase, participants were warned about the phenomenological differences between true and false memories and were instructed to use this information to avoid reporting nonpresented items. This type of warning was ineffective at reducing false recall (Experiment 2) and false recognition (Experiment 3) relative to unwarned participants. Importantly, the inability of explicit warnings to impact illusory recollections demonstrates that the false memories cannot be attributed simply to a criterion shift.     

Normative data for semantically associated Spanish word lists that create false memories

The present study provides norms for Spanish word lists that have been used to create false memories in native speakers of Spanish. The word lists reported are based on the Roediger and McDermott (1995) lists that have been used extensively to examine illusory memories. We employed Roediger and McDermott’s critical lures, translated them into Spanish, and created semantically associated Spanish word lists by testing native Spanish speakers. The resulting lists were then normed with additional native Spanish speakers. Overall, the participants recalled 53% of the list items and 32% of the critical lures with the word lists developed. In addition, 74% of the list items and 69% of the critical lures were recognized by the participants. The present study adds to the literature by providing a set of Spanish lists that can be used by researchers interested in evaluating false memories in individuals who speak Spanish. These norms may be downloaded from www.psychonomic.org/archive.     

Category structure and created memories

Cued recall of categorized lists was used to examine effects of category structure on the creation of false memories. In three experiments, category members that had not been presented on studied categorized lists were nonetheless recalled by participants. Delaying the category cued recall test (Experiment 1) and priming category members that had been omitted from target lists (Experiment 3) increased the frequency of false recall. All three experiments showed that nonpresented category members that were higher in output dominance were more frequent intrusions. The typicality of category members, however, did not uniquely contribute to the predictability of false recall (or accurate recall) once the contribution of output dominance was taken into account, suggesting that item accessibility (related to output dominance) may be more instrumental than item distinctiveness (related to typicality) in causing certain types of false recall. The results show that created memories in category cued recall are strongly biased by prior category knowledge and can be predicted by the graded structure of categories, particularly in terms of the output dominance of category instances.     

Assessing the effectiveness of warnings and the phenomenological characteristics of false memories

The phenomenology of false memories was investigated in three experiments in which participants heard two experimenters read lists of items that were related to critical nonpresented items. In Experiments 1, following a recognition memory test, participants rated the phenomenological characteristics of their memories immediately and after a 48-hour delay. False recognition was prevalent and on several dimensions participants rated their true memories as more vivid than their false memories. In Experiments 2 and 3, following the study phase, participants were warned about the phenomenological differences between true and false memories and were instructed to use this information to avoid reporting nonpresented items. This type of warning was ineffective at reducing false recall (Experiment 2) and false recognition (Experiment 3) relative to unwarned participants. Importantly, the inability of explicit warnings to impact illusory recollections demonstrates that the false memories cannot be attributed simply to a criterion shift.     

Explaining the persistence of false memories: a proposal based on associative activation and thematic extraction

This study aimed to analyse the effect of retention intervals on associative and thematic false memories. Two experiments, using two types of critical items that were either associatively or thematically related to studied material, were conducted. In both experiments, one group of participants performed a recognition test immediately after the presentation of lists, and another group performed the task one week later. In Experiment 1, the recognition test consisted of pairs of items with four response alternatives (both items had been presented, only the left item had been presented, only the right item had been presented or none of the items had been presented). Critical items were also manipulated so that they were either presented in or absent from the list. In Experiment 2, a standard recognition test that differed in the mode of presentation was used: self-paced or speeded response. Both experiments showed that associative critical items were more recognised than thematic critical items in the immediate condition. However, whereas associative critical items decayed after a one-week delay, thematic critical items were similarly recognised at both retention intervals. The findings of the present study suggest that each type of process – associative and thematic – behave differently over time.     

The influences of partner accuracy and partner memory ability on social false memories

In this study, we examined whether increasing the proportion of false information suggested by a confederate would influence the magnitude of socially introduced false memories in the social contagion paradigm Roediger, Meade, & Bergman (Psychonomic Bulletin & Review 8:365–371, 2001). One participant and one confederate collaboratively recalled items from previously studied household scenes. During collaboration, the confederate interjected 0 %, 33 %, 66 %, or 100 % false items. On subsequent individual-recall tests across three experiments, participants were just as likely to incorporate misleading suggestions from a partner who was mostly accurate (33 % incorrect) as they were from a partner who was not at all accurate (100 % incorrect). Even when participants witnessed firsthand that their partner had a very poor memory on a related memory task, they were still as likely to incorporate the confederate’s entirely misleading suggestions on subsequent recall and recognition tests (Exp. 2). Only when participants witnessed firsthand that their partner had a very poor memory on a practice test of the experimental task itself were they able to reduce false memory, and this reduction occurred selectively on a subsequent individual recognition test (Exp. 3). These data demonstrate that participants do not always consider their partners’ memory ability when working on collaborative memory tasks.     

Recall accuracy and illusory memories: when more is less

In two experiments it was revealed that manipulations that increased recall of studied list items also increased false recall of theme-related, critical nonpresented words. In Experiment 1 subjects listened to a series of short word lists, each containing items associatively related to a theme, while engaging in either semantic or nonsemantic processing. On an immediate free recall test semantic processors demonstrated greater correct recall as well as more illusory memories of critical nonpresented items than nonsemantic processors. In Experiment 2, the short study lists were combined to form longer lists that were presented either blocked by theme or in a random presentation order. Retention interval was also varied as participants were tested either immediately, one week after, or three weeks after the study phase. Presenting the target items in a blocked, as opposed to random, format increased recall accuracy, but this was at the expense of a higher intrusion rate for theme-consistent items. Interestingly, the level of false memories was not affected by retention interval even though typical decrements in the recall of study items were observed over time. The results of these experiments highlight the persistence of the false memory effect, as well as pointing to several factors, primarily semantic processing, that may lead to the creation of false memories. Interpretations are offered within the theoretical frameworks of source monitoring and fuzzy trace theory.     

Part-set cuing of false memories

Part-set cuing inhibition describes the common finding that re-presenting items from a word list can reduce subjects’ overall recall performance for studied items. Do part-set cuing effects occur for false memories as well? In the present experiments, subjects studied lists of words drawn from Roediger and McDermott (1995). After studying each list, subjects completed math problems and then recalled the list items either with or without accompanying list cues. In Experiment 1, the recall cues consisted of items drawn randomly from the original list. In Experiment 2, an additional type of cued recall task was added in which the even numbered list items were used as cues. Taken together, these experiments demonstrate robust part-set cuing effects for critical nonpresented items. In addition, they show that whereas recall of critical words is reduced by the presence of cues at test, retrieval cues do not affect critical words and studied words in exactly the same manner.     

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.     

Metamemory and reality monitoring

Metamemory judgements and reality monitoring judgements were compared for real and imagined stimuli. Line drawings of everyday items were either perceived or imagined in differing ratios, to (a) investigate people's ability to predict the class of item that would be better recalled (Judgements of Learning, JOL), and the class of item which would be better sourced (Judgements of Source, JOS) in a future recall test, and (b) test the hypothesis that participants would show a bias towards calling remembered items real when the source had been forgotten. Although participants' JOLs indicated that they believed real items would be more memorable than imagined, in both experiments a larger proportion of items from either class (real or imagined) was only recalled when presentation modality was less frequent for that class. By contrast, JOSs were no different for real or imagined items, even though source attribution was more accurate for real than imagined items. An attribution of memories to real rather than to imagined events that often occurs when participants are unsure about the source (labelled a ‘bias towards the real’) was due to phenomenological qualities of the memories. The results are discussed in terms of Johnson and Raye's ( 1981 ) reality‐monitoring model. Copyright © 2002 John Wiley & Sons, Ltd.     

Compelling untruths: content borrowing and vivid false memories

False memories are sometimes accompanied by surprisingly vivid experiential detail that makes them difficult to distinguish from actual memories. Such strikingly real false memories may be produced by a process called content borrowing in which details from presented items are errantly borrowed to corroborate the occurrence of the false memory item. In 2 experiments using think-out-loud protocols at both study and test, evidence for content borrowing occurred for more than half of the false remember judgments participants reported. The present study also provides evidence consistent with recollection rejection and distinctiveness playing a role in false-memory editing.     

False memories: young and older adults think of semantic associates at the same rate, but young adults are more successful at source monitoring

Two experiments explored whether the higher vulnerability to false memories in the DRM (J. Deese, 1959; H. L. Roediger & K. B. McDermott, 1995) paradigm in older compared to young adults reflects a deficit in source monitoring. In both experiments, adding together the number of falsely recalled critical lures and the number of critical lures produced on a post-recall test asking participants to report items that they had thought of but did not recall, indicated that the critical lures were activated during the experiment equally often in young and older adults. However, older adults were more likely than young adults to say that they had actually heard the lures. When strongly encouraged to examine the origin of memories (Experiment 2), the warning substantially reduced false recall in young but not older adults. These results are consistent with the idea that older adults have more difficulty later identifying the source of information that was activated as a consequence of intact semantic activation processes.     

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.     

The effects of social pressure on false memories

The present experiments were designed to examine the effects of social pressure on false memories. Participants studied lists created to elicit false memories and then worked in conjunction with virtual confederates on a recognition memory task. In Experiment 1, participants worked with one or two confederates to complete multiple study-test trials. On the group tests, participants were implicitly pressured to recognize words that did not appear on the studied lists. Experiment 2 was implemented similarly, but utilized a presumably more difficult recognition test involving one long study phase followed by one long test phase. After the purported group tests in both experiments, participants completed surprise individual recognition tests. In both experiments, social pressure influenced participants' responses on group recognition tests and subsequent individual recognition tests. Furthermore, the results indicated that social pressure affected both veridical memories and false memories.     

Social Contagion in Competitors Versus Cooperators

The current study examined social contagion—or the spreading of memories from individual to individual—in two different social contexts: Competition and Cooperation. Participants were provided with words (Experiments 1A and 1B) or scenes (Experiment 2) to study. After study, participants were randomly divided: Half were given a competitive context, and the other half, a cooperative context. Then, in the paired recall phase, each participant took turns with a confederate partner in recalling the previously studied items. On a subsequent test, participants had to report the items that were recalled on the pair recall phase, in addition to who had recalled that item. The results showed that competitors, as compared with cooperators, were more likely to focus on other people's memories, and surprisingly, the same difference obtained for false memories. Essentially, people who are primed with a competitive context were more easily ‘infected’ by memories, true or false. Copyright © 2015 John Wiley & Sons, Ltd.     

Working memory predicts the rejection of false memories

The relationship between working memory capacity (WMC) and false memories in the memory conjunction paradigm was explored. Previous research using other paradigms has shown that individuals high in WMC are not as likely to experience false memories as low-WMC individuals, the explanation being that high-WMC individuals are better able to engage in source monitoring. In the memory conjunction paradigm participants are presented at study with parent words (e.g., eyeglasses, whiplash). At test, in addition to being presented with targets and foils, participants are presented with lures that are composed of previously studied features (e.g., eyelash). It was found that high-WMC individuals had lower levels of false recognition than low-WMC individuals. Furthermore, recall-to-reject responses were analysed (e.g., “I know I didn't see eyelash because I remember seeing eyeglasses”) and it was found that high-WMC individuals were more likely to utilise this memory editing strategy, providing direct evidence that one reason that high-WMC individuals are not as prone to false memories is because they are better able to engage in source monitoring.     

The incidence of false memories in native and non-native speakers

The current study consisted of four experiments that utilised a novel approach to investigating false memories. Each of the experiments in the current study investigated individuals with varying experience with different languages. Experiment 1 tested participants in both their native and secondary languages as well as monolingual English speakers, while Experiment 2 assessed native Spanish speakers using both English and Spanish associative lists. Experiment 3 examined the illusory memories in monolingual Spanish speakers in both English and Spanish, while Experiment 4 investigated false memories in monolingual English speakers in both English and Spanish. Results indicated that memory for list items and critical lures was greatest when the lists were presented in the participants' primary language. Results can be explained by either activation-based or fuzzy-trace theories.     

True and intentionally fabricated memories

The aim of the experiment reported here was to investigate the processes underlying the construction of truthful and deliberately fabricated memories. Properties of memories created to be intentionally false (fabricated memories) were compared to properties of memories believed to be true (true memories). Participants recalled and then wrote or spoke true memories and fabricated memories of everyday events. It was found that true memories were reliably more vivid than fabricated memories and were nearly always recalled from a first-person perspective. In contrast, fabricated differed from true memories in that they were judged to be reliably older, were more frequently recalled from a third-person perspective, and linguistic analysis revealed that they required more cognitive effort to generate. No notable differences were found across modality of reporting. Finally, it was found that intentionally fabricated memories were created by recalling and then “editing” true memories. Overall, these findings show that true and fabricated memories systematically differ, despite the fact that both are based on true memories.