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.     

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.     

Effects of prior knowledge and response bias upon recognition memory for a story: Implications for children's eyewitness testimony

Abstract: The present study was designed to evaluate the integration hypothesis and the response bias hypothesis for explaining the fragility of children's eyewitness memory, by varying the plausibility of postevent information and the strength of response bias in recognition tests. Preschool children were told a story in which a boy named Ken saw a housebreaker stealing various objects and the postevent information was also incorporated into the story. The first recognition test was administered immediately following the presentation of an interpolated story, and the second recognition test was administered 10 weeks later. The results indicated that high-plausibility objects tended to be recognized as the stolen objects in the second recognition test, and that recognition accuracy was higher for a new-distractor condition than for a misleading-distractor condition. These findings were interpreted as suggesting that the memory representation of the story might be changed through the integration processes and/or rendered inaccessible in terms of the response bias.     

Infants' eyewitness testimony: Effects of postevent information on a prior memory representation

In eyewitness testimony research, postevent information impair retention of the original event and increases the probability that interpolated information will be identified as part:of the original event. The present experiments studied these effects with 3-month-olds. Infants learned to kick to move a particular crib mobile and then were briefly exposed to information about a novel mobile. The novel postevent information impaired recognition of the-original mobile when it immediately followed training but not when it was delayed by 1 day. Like adults, infants treated the postevent information as part of the original training event, continuing to do so for at least 2 weeks. We propose that postevent information displaces conflicting information coactive with it in primary memory and creates a new, updated memory token of the event. Once the new token leaves primary memory, however, it is protected; only a copy can be retrieved and modified in the future.     

Misleading postevent information and memory for events: arguments and evidence against memory impairment hypotheses

The claim that a person's memory for an event may be altered by information encountered after the event has been influential in shaping current conceptions of memory. The basis for the claim is a series of studies showing that subjects who are given false or misleading information about a previously witnessed event perform more poorly on tests of memory for the event than subjects who are not misled. In this article we argue that the available evidence does not imply that misleading postevent information impairs memory for the original event, because the procedure used in previous studies is inappropriate for assessing effects of misleading information on memory. We then introduce a more appropriate procedure and report six experiments using this procedure. We conclude from the results that misleading postevent information has no effect on memory for the original event. We then review several recent studies that seem to contradict this conclusion, showing that the studies do not pose problems for our position. Finally, we discuss the implications of our conclusions for broader issues concerning memory.     

Now you see it; now you don't: inhibiting recall and recognition of scenes

Postevent misleading information can distort people's memories by altering and adding scenes. But can you also inhibit the retrieval of information from memory? In two studies we show that postevent information can make memory for a scene less accessible. In both studies participants first saw an event (e.g. a restaurant scene displayed in slides, or a drunk‐driving incident shown via a video clip). Later they were shown the same event without a critical scene and were told either to use this to generate a story (Experiment 1) or to imagine the event (Experiment 2). Finally they were tested. Relative to controls, this postevent omission led to fewer people reporting the critical scene in free recall and in recognition. Thus, we demonstrated that it may be possible to inhibit memories. This finding has important implications for eyewitness testimony and the recovered memory debate. Copyright © 2001 John Wiley & Sons, Ltd.     

The effect of postevent information on adults' eyewitness reports

The present experiment examined the conditions under which adults' reports of an event are influenced by information encountered after the event occurred. Adults were exposed to neutral, leading, and misleading postevent information about a target event 24 hours after that event. Twenty‐four hours after exposure to postevent information, participants were first asked a general, open‐ended question (free recall test procedure) and were then asked a series of specific questions. Some participants were asked to select their response from two possible alternatives (recognition test procedure) and some participants were required to generate their own answers to the same questions (directed recall test procedure). The nature of the original information, the nature of the postevent information, and the specificity of the questioning procedure influenced the number of correct responses and the number of misleading errors that participants made. These findings have important implications for interviewing adult witnesses. Copyright © 2001 John Wiley & Sons, Ltd.     

Similarity of encoding context does not influence resistance to memory impairment following misinformation

Several recent studies have shown that exposure to verbal misleading post-event information does not impair subjects' ability to retrieve originally seen details. Two experiments were conducted to test the hypothesis that subjects would be more susceptible to memory impairment if the original and misleading information were presented in similar contextual formats. The results showed that misleading information did not lead to memory impairment when both original and misleading information were presented in the context of slides (Experiment 1) or when both original and misleading information were presented in the context of narratives (Experiment 2). Furthermore, resistance to memory impairment was observed both at relatively low levels of memory for the original information (Experiment 1) and at relatively high levels of memory for the original information (Experiment 2). The implications of the present results for interference principles of forgetting are discussed.     

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.     

The fate of memory: comment on McCloskey and Zaragoza

McCloskey and Zaragoza (1985) argue that misleading postevent suggestions do not affect the availability of originally encoded information. Their hypothesis stems from empirical work using a modified paradigm in which no effect of postevent information is observed. Although their "no impairment" hypothesis is plausible, careful consideration of the predictions of their experimental test suggests that it may be insufficiently sensitive to reveal the impact of postevent information. A small effect of postevent information can be observed when their paradigm is repeated with a more sensitive recognition test. McCloskey and Zaragoza's no impairment hypothesis is also difficult to reconcile with numerous reports of "blend" memories that reflect a compromise between the original and postevent information.     

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.     

Mental reinstatement of the misinformation context and the misinformation effect in children and adults

The present study investigated the effects of mental reinstatement of the context in which misleading information about an event was presented on later recognition memory for the event. Five‐year‐olds, 7‐year‐olds and adults were shown a short video depicting a children's adventure and were asked a set of misleading questions to introduce misinformation one week later. Before the recognition memory test was administered another week later, half of the participants were given instructions to mentally reinstate the context of the misleading interview. Memory was assessed with a set of forced‐choice recognition questions once in the misleading interview context and for the children a second time at home one week later. When participants were instructed to mentally reinstate the context of the misleading interview prior to the recognition test, false memory reports occurred more often for adults than for children and had a stronger impact on peripheral information than on central information for both 7‐year‐olds and adults. When 5‐ and 7‐year‐olds were tested at home, false memory reports decreased. Thus, reinstating the context of an interview introducing misinformation can reduce the accuracy of memory reports; the context dependence of both accurate and inaccurate memory reports in children and adults is discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Misleading postevent information: Testing parameterized models of integration in memory

A classic series of experiments by Loftus, Miller and Burns (1978) showed that a person's recollection of an event can be changed by misleading postevent information. Several hypotheses accounting for this effect have been proposed. Loftus' hypothesis of destructive updating claims that the original memory is destroyed by the postevent information. The coexistence hypothesis asserts that the older memory survives but is rendered inaccessible through a mechanism of inhibition or suppression. The non-conflict hypothesis simply accounts for the effect by claiming that subjects can only be misled if they did not encode or if they forgot the original event. These three hypotheses were modelled with the help of all-or-none probabilistic event trees. An experiment was conducted in order to test the three models and to assess parameter values. The experiment followed the classic Loftus paradigm. We suggested to some subjects that they had seen a stopsign, whereas in fact they had seen a traffic light. The misleading postevent information resulted in poorer reproduction of traffic light. Later, all subjects were asked whether they could remember the color of the traffic light, even if they believed they had seen a stopsign. The results showed that subjects who received the misleading post-event information were at least as good at recalling the color of the traffic light as subjects who did not receive misleading information. The no-conflict model accounts well for the obtained results, although the two other, less parsimonious, models cannot be entirely rejected.     

Amalgamations of memories: intrusion of information from one event into reports of another

Numerous researchers have reported that exposure to misleading postevent information (MPI) regarding details in a witnessed event can lead people to report false details from the MPI when asked to report the witnessed event. In such studies, the MPI is presented to participants in the context of information about the witnessed event. This experiment tests the hypothesis that postevent exposure to information that participants know is not about the witnessed event can, nonetheless, affect performance on tests of memory for that event. As predicted, when asked to report details of an event depicted in a slide show, participants tended to intrude details mentioned in a recent postevent narrative that described a different event. © 1998 John Wiley & Sons, Ltd.     

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.     

Editing misleading information from memory: Evidence for the coexistence of original and postevent information

When misleading postevent information biases one’s memory for an event, what is the fate of the original, accurate information? One possibility is that the new information and the original information coexist in memory, but that the former is simply more accessible. A second hypothesis suggests that the new information replaces the old, and memory is irreversibly altered. Using various retrieval techniques, Loftus and her associates (Greene, Flynn, & Loftus, 1982; Loftus, 1979a, 1979b) have failed repeatedly in attempts to recover original memories after postevent biasing, a finding that supports the alteration hypothesis. In the present study, postevent biasing was demonstrated in two experiments. In each experiment, some subjects were given a warning that the postevent information had included a few inaccurate details. These subjects were able to edit out the inaccurate details and to recover the original facts when the warning came as much as 45 rain after they had read the misleading information, a result that argues for the coexistence of memories. Successful recovery of the original memories was apparently due to the clarity of the warning and to an improved technique for assessing the retrieval of original memories.     

Unspecific postevent information,attribution of responsibility,and eyewitness performance

A large number of experiments have demonstrated that misleading postevent information may result in distortions of eyewitness performance. However, most studies have employed a quite specific piece of misinformation (the colour of a car, a type of a road sign) rather than more general postevent information. In the present experiment subjects viewed a film depicting a traffic accident and were subsequently informed that the car driver had or had not committed hit-and-run behaviour and that the motorcyclist had or had not been drinking. An additional control group received no information. In a subsequent interrogation subjects were asked to rate the amount of cause, responsibility and guilt attributable to the car driver and motorcyclist. Results showed that responsibility and guilt and the statements on the accident-related behaviour were influenced by the postevent information. In general, subjects who had received negative information about one of the persons involved attributed higher amounts of responsibility and guilt to them and provided more negative statements concerning their behaviour. However, details that were not closely related to the accident were not significantly influenced by postevent information. The results are discussed in terms of schematic memory reports.     

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.     

Children's Eyewitness Suggestibility: Memory Trace Strength Revisited

This study investigated memory trace strength and the eyewitness suggestibility effect in 5- and 9-year-old children. Children were first presented with a picture story and then, on the next day, were read a post-event summary containing a number of misleading details. Trace strength was manipulated by repetition of the original and/or the post-event details. Children were given either a standard or a modified recognition test on their memories for picture story details one day after presentation of misleading suggestions. Both age groups were found to be suggestible in each recognition test condition. On the modified test, suggestibility was greatest when the post-event trace was strong and the original trace was weak. Theoretical accounts of the suggestibility effect in children and of memory trace strength are discussed in the light of these findings.     

Memory states and memory tasks: an integrative framework for eyewitness memory and suggestibility

An integrative framework (IMP) is presented which depicts performance in eyewitness suggestibility experiments as the participants' solutions of memory tasks, depending on (a) a specified task-relevant memory base and (b) the participants' perception of the memory task. Three theoretical explanations of the effect of misleading post-event information are reinterpreted and reduced to one single core: individuals answer test questions while assuming the consistency of event and post-event information. The impact of such consistency assumptions (a) is demonstrated in a first experiment, where the usual misinformation effect obtained with the Loftus standard test procedure disappeared when the participants' consistency assumptions were destroyed prior to testing, and (b) manifests itself in a qualitative analysis of individual processing strategies for discrepancies between details. Experiment 2, employing methodological innovations suggested by IMP, examined the memory base and found no evidence for memory impairment or misattributions of post-event details to the witnessed scene. However, a follow-up study conducted four and a half months later revealed a strong tendency for such misattributions which might indicate long-term integration of information.