Psychotropic placebos reduce the misinformation effect by increasing monitoring at test

A psychotropic placebo can help people resist the misinformation effect, an effect thought to be caused by a shift to more stringent source monitoring. When this shift occurs has been unclear. To address this issue we gave some people - but not others - a phoney cognitive-enhancing drug we called R273. Shortly afterwards, everyone took part in a misinformation effect experiment. To gather evidence about source monitoring we surreptitiously recorded time to read the misleading postevent narrative, and response time at test. Our findings suggest that people shifted to more stringent source monitoring at test. Moreover, people with higher working memory capacity (WMC) performed better than people with lower WMC - but only when they were told they had received R273, a finding that fits with research showing that WMC can confer advantages in situations demanding effortful control, but not when automatic heuristics suffice.     

Psychotropic placebos create resistance to the misinformation effect

Can a placebo for a psychotropic drug help participants resist the misinformation effect? To answer this question, we gave participants a mixture of baking soda and water and told half of them that the mixture was a cognition-enhancing drug called R273 and told the other half that it was an inactive version of the drug. Shortly thereafter, all participants took part in a three-stage misinformation experiment. Compared with participants who were told that they had taken the placebo, the participants who were told that they had taken the drug reported improved cognitive abilities and were less susceptible to the misinformation effect. We provide sourcemonitoring and mindfulness accounts of our findings.     

Absolut memory distortions: alcohol placebos influence the misinformation effect

Can the simple suggestion that you have consumed alcohol affect your memory for an event? Alcohol placebos affect social behaviors but not nonsocial ones, and have not previously been shown to affect memory. We investigated the effect of alcohol placebos using materials that revealed both the social and the nonsocial influences of memory Subjects drank plain tonic water, but half were told it was a vodka and tonic; then all subjects took part in an eyewitness memory experiment. Subjects who were told they drank alcohol were more swayed by misleading postevent information than were those who were told they drank tonic water, and were also more confident about the accuracy of their responses. Our results show that the mere suggestion of alcohol consumption may make subjects more susceptible to misleading information and inappropriately confident. These results also provide additional confirmation that eyewitness memory is influenced by both nonsocial and social factors.     

Age-related changes in the misinformation effect

In these experiments, we examined the relation between age-related changes in retention and age-related changes in the misinformation effect. Children (5- and 6- and 11- and 12-year-olds) and adults viewed a video, and their memory was assessed immediately, 1 day, or 6 weeks later (Experiment 1). There were large age-related differences in retention when participants were interviewed immediately and after 1 day, but after the 6-week delay, age-related differences in retention were minimal. In Experiment 2, 11- and 12-year-olds and adults were exposed to neutral, leading, and misleading postevent information 1 day or 6 weeks after they viewed the video. Exposure to misleading information increased the number of commission errors, particularly when participants were asked about peripheral aspects of the video. At both retention intervals, children were more likely than adults to incorporate the misleading postevent information into their subsequent verbal accounts. These findings indicate that age-related changes in the misinformation effect are not predicted by age-related changes in retention.     

Reduction of the misinformation effect by arousal induced after learning

Misinformation introduced after events have already occurred causes errors in later retrieval. Based on literature showing that arousal induced after learning enhances delayed retrieval, we investigated whether post-learning arousal can reduce the misinformation effect. 251 participants viewed four short film clips, each followed by a retention test, which for some participants included misinformation. Afterward, participants viewed another film clip that was either arousing or neutral. One week later, the arousal group recognized significantly more veridical details and endorsed significantly fewer misinformation items than the neutral group. The findings suggest that arousal induced after learning reduced source confusion, allowing participants to better retrieve accurate details and to better reject misinformation.     

Priming correct information reduces the misinformation effect

The misinformation effect is a well-established phenomenon in the false memory literature, although the mechanisms that underlie it are debated. In the present study, we explored one aspect of the controversy, the fate of the original memory. We began from an activation-based view of memory, capitalizing on the well-understood processes of associative priming and spreading activation, to test the hypothesis that true and suggested information can coexist in memory. After exposure to misinformation, participants were unknowingly primed with associates of either the true or a suggested item. Misled participants who were primed for the true item performed better on a final memory test than did misled participants primed for neutral information. The results indicated that true and suggested information coexist and that retrieval is influenced by each concept's activation level at test. Implications for theories of the misinformation effect were discussed.     

Explicit warnings reduce but do not eliminate the continued influence of misinformation

Information that initially is presumed to be correct, but that is later retracted or corrected, often continues to influence memory and reasoning. This occurs even if the retraction itself is well remembered. The present study investigated whether the continued influence of misinformation can be reduced by explicitly warning people at the outset that they may be misled. A specific warning— giving detailed information about the continued influence effect (CIE)—succeeded in reducing the continued reliance on outdated information but did not eliminate it. A more general warning—reminding people that facts are not always properly checked before information is disseminated—was even less effective. In an additional experiment, a specific warning was combined with the provision of a plausible alternative explanation for the retracted information. This combined manipulation further reduced the CIE but still failed to eliminate it altogether.     

The role of self-esteem in the misinformation effect

Previous research using the Gudjonnson suggestibility scale has suggested a role for self-esteem in suggestibility, with participants low in self-esteem being more suggestible than participants high in self-esteem. Four experiments are presented examining the role of self-esteem in the misinformation effect and whether enhanced suggestibility effects in participants low in self-esteem reflect genuine memory impairment. In Experiments 1 and 4 participants completed a standard recognition test. In Experiment 2 participants completed the modified recognition test. In Experiment 3 participants completed a free recall test. In Experiments 1 and 4 participants low in self-esteem demonstrated greater misinformation effects than participants high in self-esteem. In Experiment 3 a 3-day retention interval was employed with the modified test and no differences were found between the two groups on the reporting of the new item. The findings suggest that participants low in self-esteem are particularly sensitive to demand characteristics and post-event suggestion but do not suffer from genuine memory impairment.     

Aging and the misinformation effect: a neuropsychological analysis

Older adults' susceptibility to misinformation in an eyewitness memory paradigm was examined in two experiments. Experiment 1 showed that older adults are more susceptible to interfering misinformation than are younger adults on two different tests (old-new recognition and source monitoring). Experiment 2 examined the extent to which processes associated with frontal lobe functioning underlie older adults' source-monitoring difficulties. Older adults with lower frontal-lobe-functioning scores on neuropsychological tests were particularly susceptible to false memories in the misinformation paradigm. The authors' results agree with data from other false memory paradigms that show greater false recollections in older adults, especially in those who scored poorly on frontal tests. The results support a source-monitoring account of aging and illusory recollection.     

A re-examination of the misinformation effect by means of visual and verbal recognition tests

Abstract: Two experiments were carried out to investigate the factors that produce the misinformation effect (Loftus, 1979a). Experiment 1 of the present study using the visual recognition test was a replica of Experiment 1 of Loftus, Miller, and Burns (1978). The misinformation effect was not found. Experiment 2 differed from Experiment 1 in the following respects: the modality of recognition test was varied between visual and verbal; memorableness (ease of memorization) of the critical objects was varied. The results of Experiment 2 suggest that the original visual memory might be more likely to be recovered with a visual recognition test than with a verbal recognition test, and that the postevent information would not necessarily interfere effectively with memory of an original object of too high or low memorableness, while it works well on objects of intermediate memorableness.     

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.     

Recognition performance level and the magnitude of the misinformation effect in eyewitness memory

The issue of whether misleading postevent information affects performance on the modified recognition test introduced by McCloskey and Zaragoza (1985) was examined in a meta-analysis. Results indicated that a misinformation effect can be obtained with the modified test. The meta-analysis also revealed that recognition hit rates are higher in studies that yield a misinformation effect than in studies in which the misinformation effect is not significant. The data from the meta-analysis were also used to assess whether the misinformation effect is related to the length of the retention interval. Results showed that a misinformation effect is more likely to be obtained with long retention intervals, although in the available data there is a confound between the length of the retention interval and the recognition level obtained.     

The power of the spoken word: Sociolinguistic cues influence the misinformation effect

We investigated whether the sociolinguistic information delivered by spoken, accented postevent narratives would influence the misinformation effect. New Zealand subjects listened to misleading postevent information spoken in either a New Zealand (NZ) or North American (NA) accent. Consistent with earlier research, we found that NA accents were seen as more powerful and more socially attractive. We found that accents per se had no influence on the misinformation effect but sociolinguistic factors did: both power and social attractiveness affected subjects' susceptibility to misleading postevent suggestions. When subjects rated the speaker highly on power, social attractiveness did not matter; they were equally misled. However, when subjects rated the speaker low on power, social attractiveness did matter: subjects who rated the speaker high on social attractiveness were more misled than subjects who rated it lower. There were similar effects for confidence. These results have implications for our understanding of social influences on the misinformation effect.     

The power of the spoken word: sociolinguistic cues influence the misinformation effect

We investigated whether the sociolinguistic information delivered by spoken, accented postevent narratives would influence the misinformation effect. New Zealand subjects listened to misleading postevent information spoken in either a New Zealand (NZ) or North American (NA) accent. Consistent with earlier research, we found that NA accents were seen as more powerful and more socially attractive. We found that accents per se had no influence on the misinformation effect but sociolinguistic factors did: both power and social attractiveness affected subjects' susceptibility to misleading postevent suggestions. When subjects rated the speaker highly on power, social attractiveness did not matter; they were equally misled. However, when subjects rated the speaker low on power, social attractiveness did matter: subjects who rated the speaker high on social attractiveness were more misled than subjects who rated it lower. There were similar effects for confidence. These results have implications for our understanding of social influences on the misinformation effect.     

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.     

Influence of individual differences in working memory on the continued influence effect of misinformation

ABSTRACT

Misinformation often continues to influence people’s cognition even after being retracted (the continued influence effect of misinformation, CIE). The current research aimed to investigate whether the individual differences in the central executive function of WM and updating could influence the CIE of misinformation with varying relevance. The results showed that the individual differences in central executive function could significantly affect the CIE, especially for the high-relevant misinformation. While the individual differences in the updating ability had a weaker impact on the CIE in general and only negatively related to the CIE for the low-relevant misinformation. The study extends the understanding of the relationship between individual differences and the CIE from previous studies, which is in line with the mental-model-updating hypothesis, and offers a preliminary clue for identifying the persons vulnerable to the CIE of misinformation in the real world.     

A theoretical review of the misinformation effect: Predictions from an activation-based memory model

This article reviews the major empirical results and theoretical issues from over 20 years of research on people’s acceptance of false information about recently experienced events (see, e.g., Loftus, 1975). Several theoretical perspectives are assessed in terms of their ability to account for the various and sometimes conflicting results in the literature. Theoretical perspectives reviewed include the trace alteration hypothesis, the blocking hypothesis, the task demands/strategic effects hypothesis, source monitoring, and an activation-based semantic memory account. On the basis of its ability to account for the reviewed data and other cognitive phenomena, an activation-based semantic network model of memory is suggested for understanding the data and planning future research in the area.     

Both differences in encoding processes and monitoring at retrieval reduce false alarms when distinctive information is studied

A reduction in false alarms to critical lures is observed in the DRM paradigm (Roediger & McDermott, 1995) when distinctive information is presented at encoding. Two mechanisms have been proposed to account for this reduction. According to the monitoring theory (e.g., the distinctiveness heuristic), lack of diagnostic recollection serves as a basis for discarding non-presented lures. According to the encoding theory, presenting distinctive information at study leads to impoverished relational processing, which results in a reduction in memorial information elicited by critical lures. In the present study a condition was created in which the use of the distinctiveness heuristic was precluded by associating, within the same study, lures with distinctive information in a context different from the study session. Under that condition reduction in false alarms to distinctive critical lures was still observed. This result supports the predictions of the encoding theory. However, when in the same study the use of the distinctiveness heuristic was not precluded, reductions in false alarms to unrelated lures were also observed when distinctive information was presented at study, indicating that both mechanisms are likely to contribute to the rejection of false memories.     

Warnings reduce the magnitude of the imagination inflation effect

Imagination inflation occurs when people increase their confidence that an event actually happened after imagining the details of the event. The purpose of this study was to determine whether warning people about the imagination inflation effect would reduce their tendency to inflate their ratings of the imagined events. In one condition, we warned participants about the deleterious effects of imagining distant events. Compared with a control group that did not receive a warning, this group produced a significantly smaller imagination inflation effect. We discuss these results and the imagination inflation effect in the context of 2 theories designed to explain the cognitive processes that produce this effect.