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.     

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.     

Testing potentiates new learning in the misinformation paradigm

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

The effects of misleading and inconsistent postevent information on children's recollections of criterion-learned information.

Similar experimental procedures are used in misinformation studies and in retroactive inhibition studies. Despite these similarities, the findings of these studies have suggested that misleading postevent information and inconsistent postevent information would have different effects on children's recollections. To examine this hypothesis, 28 seven-year-olds learned a target game to criterion. Two days later, they were administered either type of postevent information on either one or three occasions. When the children were tested 3 weeks later, the results showed that even criterion-learned information could be affected detrimentally by exposure to misleading or inconsistent postevent information. Notably, children who were administered misinformation on one occasion reported more target information than children in all other groups. It is suggested that exposure to misinformation had a facilitative effect on these children's recollections.     

Discrepancy detection and vulnerability to misleading postevent information

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

Influences of misleading postevent information: misinformation interference and acceptance

Because of the biasing nature of retrieval tests, evidence that the introduction of misleading postevent information will impair the memory for an original event has recently been in dispute. In two experiments, a retrieval test sensitive to both biasing effects of misinformation (misinformation acceptance) and influences of the misinformation on memory (misinformation interference) was used. Both experiments demonstrated misinformation acceptance, and one of the experiments suggested that misinformation interferes with the ability to remember the original event. Two misinformation interference hypotheses are evaluated; they suggest that the misinformation may have either impaired memory or led to confusion regarding what had occurred during the event.     

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.     

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.     

Memory strength affects reporting of misinformation

A model of long-term retention was used to examine whether and how the strength of original information (differences in learning and testing time) and the strength of misleading information (differences in timing and frequency) influence 3- to 5-year-olds' memory for an event. In three experiments, preschoolers viewed a slide presentation depicting an event, some of them were asked misleading questions, and memory for event details was tested. There was little evidence of memory impairment, but exposure to misleading information encouraged reporting of this information. Differences in learning influenced reporting in that children exposed to the event once reported more misled details than those who saw the event multiple times. Furthermore, preschoolers who saw the event once were just as susceptible to misleading information whether exposed to misinformation once or three times; however, preschoolers who had seen the event multiple times were susceptible only to repeated presentations of misinformation. Given that the reporting of misinformation is determined by the degree of integrity of both the original and misleading information, it is important to control for differences in trace strength for both types of information in future research.     

Misleading postevent information and working memory capacity: an individual differences approach to eyewitness memory

The present study examines how individual differences in working memory capacity relate to the effect of misleading postevent information on memory for the original event. Participants were shown a film of a crime event and were then asked to unscramble a narrative that included misinformation regarding some of the film's details. Additionally, the working memory capacity of the participants was measured using the operation‐word span task. Finally, in a free recall test, participants recalled fewer correct details in the misinformation condition compared to the control condition. This effect was negatively correlated with working memory capacity. Copyright © 2002 John Wiley & Sons, Ltd.     

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

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

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.     

Memory impairment in the weapon focus effect

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

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.     

Effects of the timing of postevent information on preschoolers' memories of an event

Few researchers have investigated whether the timing of postevent information affects the accuracy of children's reports of events they have experienced. In this study, four‐year‐olds dressed up in costumes and had their photographs taken. An unfamiliar adult spoke to the children about the event either a day (immediate condition) or a month (delayed condition) later, providing both accurate and misleading information about the staged event. When questioned five weeks after the event, children in a control group who had not received the review were more inaccurate answering focused questions than children who had been reminded of the event. A review a while after the event but shortly before the interview increased the amount of details recalled and this was not at the expense of accuracy. Misinformation was seldom reported spontaneously, although children in all groups acquiesced to leading questions in line with the misleading suggestions. Copyright © 1999 John Wiley & Sons, Ltd.     

Assessing the effects of misinformation on children's recall: how and when makes a difference

In two experiments children aged between 4 and 5 years and 7 and 8 years, respectively, participated in a real‐life event and were exposed to misleading questions immediately afterwards. The effects of variables relating to both the presentation of the misinformation and to the assessment of suggestibility were examined both immediately and following delays of 1 week (Experiment 1) or both 1 week and 1 month (Experiment 2). Older children were less suggestible than younger. Children were less suggestible when suggestibility was assessed in recall questions rather than misleading questions, less suggestible when information was central rather than peripheral and when the misinformation contradicted rather than supplemented the original event, and less suggestible over time in the absence of further suggestions. Providing cues had a small effect in enhancing resistance to the misinformation, but only when children were tested immediately. Embedding suggestions in a narrative context and repeating suggestions within a session led to greater suggestibility for both age groups, and repeating suggestions following a 1‐month delay had a particularly marked effect for the younger children. These findings are consistent with the view that suggestibility effects depend on the strength of the memory trace for the original information as well as that for the suggestion. How suggestibility is assessed is, however, also important and children's responses to misleading questions may not reflect their memory for the original event. Copyright © 2000 John Wiley & Sons, Ltd.     

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.     

Role of environmental context in eyewitness memory

We investigated whether varying the environmental context will affect the magnitude of retroactive interference produced by misleading postevent information in an eyewitness memory paradigm. Previous eyewitness memory studies have typically presented the original and misleading information in the same environmental context. In this experiment, the physical contexts in which the original information and the misleading information were presented were varied, a procedure that is more analogous to what usually occurs in real world situations. We tested 288 subjects, half using the original and misleading information in the same encoding context and half using a different context for presenting the two types of information. Memory for the original event was assessed using either the standard recognition test procedure or the modified test developed by McCloskey and Zaragoza (1985). Measures of both recognition accuracy and response latency showed no difference in performance attributable to varying the environmental context. The present data replicate the findings of previous single-context experiments that showed the two recognition test procedures to produce different patterns of results. Thus, environmental context seems to play little role in determining the magnitude of the misleading postevent information effect.