How eyewitnesses resist misinformation: Social postwarnings and the monitoring of memory characteristics

Previous findings have been equivocal as to whether the postevent misinformation effect on eyewitness memory is reduced by warnings presented after the misinformation (postwarnings). In the present research, social postwarnings, which characterize the postevent source as a low-credibility individual, diminished the misinformation effect in both cued recall and recognition tests. Discrediting the source as being either untrustworthy or incompetent was effective (Experiment 1). Also, postwarned participants rated reality characteristics of their memories more accurately than did participants receiving no or high-credibility information about the postevent source (Experiment 2). A social postwarning yielded the same results as an explicit source-monitoring appeal and led to longer response times for postevent items, relative to a no-warning condition (Experiments 3 and 4). The findings suggest that the reduced misinformation effect was due to more thorough monitoring of memory characteristics by postwarned participants, rather than to a stricter response criterion or to enhanced event memory.     

Features and feedback: enhancing metamnemonic knowledge at retrieval reduces source-monitoring errors

Three experiments explored the issue of whether enhanced metamnemonic knowledge at retrieval can improve participants' ability to make difficult source discriminations in the context of the eyewitness suggestibility paradigm. The 1st experiment documented differences in phenomenal experience between veridical and false memories. Experiment 2 revealed that drawing participants' attention to these differences by pairing the ratings of the features with instructions about their utility was successful in reducing source misattributions of suggested items to the event. The results of Experiment 3 showed that participants can make online adjustments in the types of evidence used to make source judgments, as participants who received correct feedback during the training portion of the test reduced misattribution errors on the remainder of the test where feedback was not provided. Altogether, these studies suggest that people can discover and benefit from updated knowledge of the types of memorial evidence that discriminate between sources of information in memory.     

I misremember it well: Why older adults are unreliable eyewitnesses

We used the eyewitness suggestibility paradigm to investigate the hypothesis that cognitive aging is associated with an increase in misrecollections—confidently held but false memories of past events. When younger and older adults were matched on their overall memory for experienced events, both groups showed comparable rates of suggestibility errors in which they claimed to have seen events in a video that had only been suggested in a subsequent questionnaire. However, older adults were—alarmingly—most likely to commit suggestibility errors when they were most confident about the correctness of their response. By contrast, their younger, accuracy-matched counterparts were most likely to commit these errors when they were uncertain about the accuracy of their response. The elderly adults’ propensity to make high-confidence errors fits our misrecollection account.     

Mechanisms of eyewitness suggestibility: tests of the explanatory role hypothesis

In a recent paper, Chrobak and Zaragoza (Journal of Experimental Psychology: General, 142(3), 827–844, 2013) proposed the explanatory role hypothesis, which posits that the likelihood of developing false memories for post-event suggestions is a function of the explanatory function the suggestion serves. In support of this hypothesis, they provided evidence that participant-witnesses were especially likely to develop false memories for their forced fabrications when their fabrications helped to explain outcomes they had witnessed. In three experiments, we test the generality of the explanatory role hypothesis as a mechanism of eyewitness suggestibility by assessing whether this hypothesis can predict suggestibility errors in (a) situations where the post-event suggestions are provided by the experimenter (as opposed to fabricated by the participant), and (b) across a variety of memory measures and measures of recollective experience. In support of the explanatory role hypothesis, participants were more likely to subsequently freely report (E1) and recollect the suggestions as part of the witnessed event (E2, source test) when the post-event suggestion helped to provide a causal explanation for a witnessed outcome than when it did not serve this explanatory role. Participants were also less likely to recollect the suggestions as part of the witnessed event (on measures of subjective experience) when their explanatory strength had been reduced by the presence of an alternative explanation that could explain the same outcome (E3, source test + warning). Collectively, the results provide strong evidence that the search for explanatory coherence influences people’s tendency to misremember witnessing events that were only suggested to them.     

Warnings reduce false memories for missing aspects of events

When people see movies with some parts missing, they falsely recognize many of the missing parts later. In two experiments, we examined the effect of warnings on people's false memories for these parts. In Experiment 1, warning subjects about false recognition before the movie (forewarnings) reduced false recognition, but warning them after the movie (postwarnings) reduced false recognition to a lesser extent. In Experiment 2, the effect of the warnings depended on the nature of the missing parts. Forewarnings were more effective than postwarnings in reducing false recognition of missing noncrucial parts, but forewarnings and postwarnings were similarly effective in reducing false recognition of crucial missing parts. We use the source monitoring framework to explain our results.     

Individual and developmental differences in eyewitness recall and suggestibility in children with intellectual disabilities

This study examined two key issues: (1) whether there were developmental improvements in eyewitness memory performance for children with intellectual disabilities (ID); and (2) whether standardised measures of cognitive ability and suggestibility would relate to eyewitness recall and suggestibility. Children with ID and age‐matched controls (ages 8/9 and 12 years) watched a video of a crime and were asked a range of open‐ended and specific questions about the event in a subsequent interview. Free recall increased between the two age levels for children with and without ID, but at a faster rate for those without ID. For other question types, differences in performance between children with and without ID were far more marked than age differences. Standardised measures of interrogative suggestibility (Gudjonsson Suggestibility Scale, GSS), verbal IQ, non‐verbal IQ, mental age and speed of information processing were related to eyewitness performance. In particular, higher eyewitness recall scores (free recall, non‐leading specific questions) were related to higher scores on the standardised GSS free recall measure; and higher eyewitness suggestibility scores were related to higher scores on the standardised GSS suggestibility measures. Mental age was a better predictor of performance on a range of eyewitness memory question types than verbal or non‐verbal IQ; and speed of information processing showed some relationships with eyewitness performance. Copyright © 2006 John Wiley & Sons, Ltd.     

The dark side of testing memory: repeated retrieval can enhance eyewitness suggestibility

Eyewitnesses typically recount their experiences many times before trial. Such repeated retrieval can enhance memory retention of the witnessed event. However, recent studies (e.g., Chan, Thomas, & Bulevich, 2009) have found that initial retrieval can exacerbate eyewitness suggestibility to later misleading information--a finding termed retrieval-enhanced suggestibility (RES). Here we examined the influence of multiple retrieval attempts on eyewitness suggestibility to subsequent misinformation. In four experiments, we systematically varied the number of initial tests taken (between zero and six), the delay between initial testing and misinformation exposure (~30 min or 1 week), and whether initial testing was manipulated between- or within-subjects. University undergraduate students were used as participants. Overall, we found that eyewitness suggestibility increased as the number of initial tests increased, but this RES effect was qualified by the delay and by whether initial testing occurred in a within- or between-subjects manner. Specifically, the within-subjects RES effect was smaller than the between-subjects RES effect, possibly because of the influence of retrieval-induced forgetting/facilitation (Chan, 2009) when initial testing was manipulated within subjects. Moreover, consistent with the testing effect literature (Roediger & Karpicke, 2006), the benefits of repeated testing on later memory were stronger after a 1-week delay than after a 30-min delay, thus reducing the negative impact of RES in long-term situations. These findings suggest that conditions that are likely to occur in criminal investigations can either increase (repeated testing) or reduce (delay) the influence of RES, thus further demonstrating the complex relationship between eyewitness memory and repeated retrieval.     

Suggestibility and state anxiety: how the two concepts relate in a source identification paradigm

Source identification tests provide a stringent method for testing the suggestibility of memory because they reduce response bias and experimental demand characteristics. Using the techniques and materials of Maria Zaragoza and her colleagues, we investigated how state anxiety affects the ability of undergraduates to identify correctly the source of misleading post-event information. The results showed that individuals high in state anxiety were less likely to make source misattributions of misleading information, indicating lower levels of suggestibility. This effect was strengthened when forgotten or non-recognised misleading items (for which a source identification task is not possible) were excluded from the analysis. Confidence in the correct attribution of misleading post-event information to its source was significantly less than confidence in source misattributions. Participants who were high in state anxiety tended to be less confident than those lower in state anxiety when they correctly identified the source of both misleading post-event information and non-misled items. The implications of these findings are discussed, drawing on the literature on anxiety and cognition as well as suggestibility.     

The effect of forced recall on illusory recollection in younger and older adults

The effect of an initial forced recall test on later recall and recognition tests was examined in younger and older adults. Subjects were presented with categorized word lists and given an initial test under standard cued recall instructions (with a warning against guessing) or forced recall instructions (that required guessing); subjects were later given a cued recall test for the original list items. In 2 experiments, initial forced recall resulted in higher levels of illusory memories on subsequent tests (relative to initial cued recall), especially for older adults. Older adults were more likely to say they remembered rather than knew that forced guesses had occurred in the original study episode. The effect persisted despite a strong warning against making errors in Experiment 2. When a source monitoring test was given, older adults had more difficulty than younger adults in identifying the source of items they had originally produced as guesses. If conditions encourage subjects to guess on a first memory test, they are likely to recollect these guesses as actual memories on later tests. This effect is exaggerated in older adults, probably because of their greater source monitoring difficulties. Both dual process and source monitoring theories provide insight into these findings.     

Investigating the effects of age and gender on cowitness suggestibility during blame attribution

Despite a large body of research investigating the effects of age and gender on eyewitness suggestibility, the majority of studies has focussed on the impressionability of participants when attempting to recall the presence of items from an event. Very little research has attempted to investigate the effects of age and gender on the suggestibility of eyewitnesses when attempting to attribute blame. Participants (N = 268) viewed and discussed a crime (video) with cowitnesses before giving individual statements. Confederates were used to expose the participants to misinformation during the discussion, suggesting that the wrong bystander was responsible for the offence. Findings indicated that participants who encountered the misinformation were more likely to make a false blame attribution and were more confident in their erroneous judgements. The results found no significant age‐ or gender‐related differences in blame conformity rates; however, male eyewitnesses showed greater levels of overconfidence in their false responses than female participants, after encountering cowitness misinformation.     

Age-appropriate cues facilitate source-monitoring and reduce suggestibility in 3- to 7-year-olds

Providing cues to facilitate the recovery of source information can reduce postevent misinformation effects in adults, implying that errors in source-monitoring contribute to suggestibility (e.g., [Lindsay, D. S., & Johnson, M. K. (1989). The eyewitness suggestibility effect and memory for source. Memory & Cognition, 17, 349–358]). The present study investigated whether source-monitoring plays a similar role in children’s suggestibility. It also examined whether the accuracy of source judgements is dependent on the type of source task employed at test. After watching a film and listening to a misleading narrative, 3–4- and 6–7-year-olds (n = 116) were encouraged to attend to source memory at retrieval. This was achieved either via sequential “question pairs”, which are typically used in children’s source-monitoring research, or via a novel “posting-box” procedure, in which all source options were provided simultaneously. Performance elicited by each type of source task was compared with that evoked by old/new recognition procedures. Posting-box, but not question pair, source cues were effective at reducing the magnitude of the suggestibility effect, relative to that observed under recognition conditions. Furthermore, source question pairs provoked a bias to respond affirmatively for 3–4-year-olds. The findings imply that children’s suggestibility may be partially explained by sub-optimal use of intact source information, which may be activated by age-appropriate strategies at retrieval.     

Contextual overlap and eyewitness suggestibility

Studies of eyewitness suggestibility have traditionally used a paradigm that maximizes the extent to which the postevent interview overlaps with the witnessed event in terms of narrative content, narrative structure, and environmental context. The present study explored whether these dimensions of overlap contribute to people's tendency to confuse suggested details for those they have actually witnessed. We systematically manipulated the extent to which the postevent questionnaire overlapped with the witnessed event. Across two experiments, overlap in narrative content, narrative structure, or environmental context was not found to increase suggestibility effects, even though the manipulation did have other memory effects (e.g., it improved cued recall of the actual source of the suggestions, Experiment 2). These findings suggest that understanding the interaction between the structure and content of the objective context in which misinformation is encountered and various remembering contexts (e.g., recognition vs. recall) is important for advancing our understanding of source confusion in an eyewitness situation.     

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.     

Suggestibility and source monitoring errors: blame the interview style,interviewer consistency,and the child's personality

Sixty children were forced to confabulate or given misinformation about a simulated crime. Higher suggestibility in the forced confabulation group than in the suggestive group occurred even after 1 week. Interview source errors in the forced confabulation group were higher for confabulations when asked by the same person, but for control items when asked by a different person. Interview source errors in the suggestive group were higher for confabulations when asked by a different person, but for control items when asked by the same person. Confabulations were misattributed to the video by the forced confabulation more than the suggestive group. However, both groups mistakenly believed they had previously discussed control true‐event items. Suggestibility was high when imaginative and dissociative children were forced to confabulate. Control false‐event items were misattributed to the interview by compliant children and to the video by imaginative children in the forced confabulation group. Shy children in the forced confabulation group misattributed confabulations to the video, whereas distractible children in the suggestive group misattributed control false‐event items to both sources. Copyright © 2005 John Wiley & Sons, Ltd.     

Hypnotic pseudomemories,prehypnotic warnings,and the malleability of suggested memories

This study used Orne's nocturnal events paradigm to test the effects of warning highly hypnotizable participants about the possibility of hypnotic false memories. We found that warnings reduced suggestibility but not false memories during hypnosis. Fewer warned participants (12/32, 38 per cent) than unwarned participants (12/16, 75 per cent) accepted the suggestion to hear a noise that awakened them when they were age-regressed to a night of the previous week. However, an analysis of only those persons who accepted the suggestion during hypnosis showed that the warning had no effect on their posthypnotic pseudomemories: among this group, 75 per cent of warned versus 58 per cent of unwarned persons stated immediately after hypnosis that the noise occurred in reality (i.e., reported a pseudomemory). During a final confidential assessment, 58 per cent of the warned participants who had accepted the noise suggestion reported a pseudomemory, versus 50 per cent of the unwarned participants. Comparing pseudomemory rates across all participants, regardless of whether they passed or failed the noise suggestion, 28 per cent of warned participants versus 44 per cent of unwarned participants reported pseudomemories, a nonsignificant difference. Finally, warned and unwarned participants were equally confident in their false memories. © 1998 John Wiley & Sons, Ltd.     

The use of source memory to identify one's own episodic confusion errors

In 4 category cued recall experiments, participants falsely recalled nonlist common members, a semantic confusion error. Errors were more likely if critical nonlist words were presented on an incidental task, causing source memory failures called episodic confusion errors. Participants could better identify the source of falsely recalled words if they had deeply processed the words on the incidental task. For deep but not shallow processing, participants could reliably include or exclude incidentally shown category members in recall. The illusion that critical items actually appeared on categorized lists was diminished but not eradicated when participants identified episodic confusion errors post hoc among their own recalled responses; participants often believed that critical items had been on both the incidental task and the study list. Improved source monitoring can potentially mitigate episodic (but not semantic) confusion errors.     

Learning errors from fiction: Difficulties in reducing reliance on fictional stories

Readers rely on fiction as a source of information, even when fiction contradicts relatively well-known facts about the world (Marsh, Meade, and Roediger, 2003). Of interest was whether readers could monitor fiction for errors, in order to reduce suggestibility. In Experiment 1, warnings about errors in fiction did not reduce students' reliance on stories. In Experiment 2, all subjects were warned before reading stories written at 6th- or 12th-grade reading levels. Even though 6th-grade stories freed resources for monitoring, suggestibility was not reduced. In Experiment 3, suggestibility was reduced but not eliminated when subjects pressed a key each time they detected an error during story reading. Readers do not appear to spontaneously monitor fiction for its veracity, but can do so if reminded on a trial-by-trial basis.     

The role of attachment and cognitive inhibition in children's memory and suggestibility for a stressful event

There has been increasing interest in children's abilities to report memories of and resist misleading suggestions about distressing events. Individual differences among children and their parents may provide important insight into principles that govern children's eyewitness memory and suggestibility for such experiences. In the present study, 51 children between the ages of 3 and 7 years were interviewed about an inoculation after a delay of approximately 2 weeks. Results indicated that parents' attachment Avoidance was associated with children's distress during the inoculation. Parental attachment Anxiety and the interaction between parental Avoidance and children's stress predicted children's memory for the inoculation. Cognitive inhibition was also a significant predictor of children's memory errors and suggestibility. Theoretical implications concerning effects of stress and individual differences on children's eyewitness memory and suggestibility are discussed.