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.     

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.     

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.     

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.     

Breaking script: Deviations and postevent information in adult memory for a repeated event

Witnesses to industrial incidents may be asked to recall a single instance of a familiar event. This research systematically tested if deviations to what typically occurs and postevent information (PEI) enhanced reporting of an instance of a repeated event. Across 2 experiments, each participant experienced 5 food‐tasting instances; these instances comprised the repeated event. Half of the participants in both Experiments 1 (continuous deviation setting) and 2 (continuous deviation integrated) experienced a deviation to how the third instance occurred. Also, half of the participants in both experiments received PEI about the third instance. All participants demonstrated superior reporting for the first instance of the repeated event. The continuous deviation setting in Experiment 1 enhanced reporting for all 5 instances of the repeated event (general effect). In Experiment 2, participants who received a continuous deviation integrated and PEI demonstrated superior reporting for the first and third instances of the event (targeted effect).     

Dimension integration: Testing models without trade-offs

This paper tests a behavioral property called dimension integration. The test evaluates models, such as lexicographic semi-orders and the priority heuristic, which assume that a person uses only one dimension at a time. It provides a way to compare such models against those that assume a person combines information from different dimensions. The test allows one to test the hypothesis that different people use different lexicographic semi-orders with different threshold parameters. In addition, by use of a “true and error” model, it is possible to “correct” for unreliability of choice in order to estimate the proportions of participants who show different response patterns that can be classified as integrative or not integrative. An experiment with 260 participants was conducted in which people made choices between two-branch gambles. The aggregate results violate the priority heuristic and six lexicographic semi-orders. The data also refute the theory that people use a mixture of these lexicographic semi-orders. In addition, few individuals appear to show response patterns consistent with non-integrative models. Instead, they show that most individuals show patterns consistent with the hypothesis that they combine information between dimensions.     

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.     

Experiments and models in sequential integration of information

Using the example of bimodal temporal order judgments, we investigate and explain the transition from static designs mapping single stimulus presentations to single responses to designs which require some kind of integration of the processed information. First, we estimate the parameters of several well-known channel-oriented models (Baron, 1969; Gibbon & Rutschmann, 1969) for temporal order judgments. Subsequently, we generalize these models to explain the results of two more complex experimental designs and derive and test their predictions. Special concern is given to the question whether or not the models parameters remain invariant across the experiments. The basic assumptions of the channel-oriented models are confirmed by our data, they represent a well-suited platform to explain more complex integrative processes. Within a sequential decision design, where subjects are allowed to observe a stimulus arbitrarily often before their terminal decision, the individual representations of the stimuli are additively integrated. Hence, even information, which did not yet lead to a terminal decision, will generally influence the later outcome. This representation of the stimuli is accompanied by a dynamic decision rule, which is clearly time-dependent. Several too simplizistic alternative models can be rejected if (and only if) one derives their predictions in some detail and tests them with sufficient statistical power.     

But I thought it was Mickey Mouse: the effects of new postevent information on 18-month-olds' memory

Two experiments examined the effects of postevent information on 18-month-olds' event memory. Experiment 1 (N=60) explored whether children's memory was reinstated when action information was eliminated from the reinstatement and only object information was introduced. Experiment 2 (N=48) examined children's recall when either (a). information about the objects' target actions was replaced with new action information or (b). the original training objects were replaced with new objects. In an elicited-imitation paradigm, children were trained to perform six target actions, watched a video reinstatement 10 weeks later, and were tested for recall 24 h after reinstatement. Two results were found. First, a video reminder eliminating action information reinstated children's memory as effectively as a video containing object and action information. Second, children were reminded of their past training when during reinstatement action information was preserved and new objects were presented but were not reminded when object information was preserved and new actions were presented.     

Category typicality effects in episodic memory: Testing models of distinctiveness

Middle Tennessee State University, Murfreesboro, Tennessee Category typicality effects were investigated within the context of three models of distinctiveness: a univariate model, a fixed-multifeature model, and a weighted-multifeature model. High-typical, medium-typical, and atypical targets were embedded in lists containing a background set of mediumto high-typicality items. Atypical items were more poorly recalled than were medium- and high-typical items independently of list structure. In recognition, subjects who studied high-typical items had difficulty discriminating between high-typical items that were and were not presented as part of the list. However, item typicality had little effect on the recognition performance of subjects who did not study high-typical items. These findings were consistent with the weighted-multifeature model of distinctiveness.     

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.     

Semantic integration of verbal information into a visual memory

A total of 1,242 subjects, in five experiments plus a pilot study, saw a series of slides depicting a single auto-pedestrian accident. The purpose of these experiments was to investigate how information supplied after an event influences a witness's memory for that event. Subjects were exposed to either consistent, misleading, or irrelevant information after the accident event. Misleading information produced less accurate responding on both a yes-no and a two-alternative forced-choice recognition test. Further, misleading information had a larger impact if introduced just prior to a final test rather than immediately after the initial event. The effects of misleading information cannot be accounted for by a simple demand-characteristics explanation. Overall, the results suggest that information to which a witness is exposed after an event, whether that information is consistent or misleading, is integrated into the witness's memory of the event.     

The representation and integration in memory of spatial and nonspatial information

A series of experiments investigated whether people could integrate nonspatial information about an object with their knowledge of the object's location in space. In Experiments 1 and 3, subjects learned the locations of cities on a fictitious road map; in Experiments 2, 4, and 5, subjects were already familiar with the locations of buildings on a campus. The subjects then learned facts about the cities on the maps or the buildings on the campus. The question of interest was whether or not these nonspatial facts would be integrated in memory with the spatial knowledge. After learning the facts, subjects were given a location-judgment test in which they had to decide whether an object was in one region of the space or another. Knowledge integration was assessed by comparing levels of performance in two conditions: (a) when a city or a building name was primed by a fact about a neighboring city or building, and (b) when a city or a building name was primed by a fact about a distant city or building. Results showed that responses in Condition a were faster or more accurate, or both faster and more accurate, than responses in Condition b. These results indicate that the spatial and nonspatial information were encoded in a common memory representation.     

Testing global memory models using ROC curves.

Global memory models are evaluated by using data from recognition memory experiments. For recognition, each of the models gives a value of familiarity as the output from matching a test item against memory. The experiments provide ROC (receiver operating characteristic) curves that give information about the standard deviations of familiarity values for old and new test items in the models. The experimental results are consistent with normal distributions of familiarity (a prediction of the models). However, the results also show that the new-item familiarity standard deviation is about 0.8 that of the old-item familiarity standard deviation and independent of the strength of the old items (under the assumption of normality). The models are inconsistent with these results because they predict either nearly equal old and new standard deviations or increasing values of old standard deviation with strength. Thus, the data provide the basis for revision of current models or development of new models.     

The Morton-Massaro law of information integration: implications for models of perception

Information integration may be studied by analyzing the effect of 2 or more sources (e.g., auditory and visual) on participants' responses. Experiments show that ratios of response probabilities often factorize into components selectively influenced by only 1 source (e.g., 1 component affected by the acoustic source and another 1 affected by the visual source). This is called the Morton-Massaro law (MML). This article identifies conditions in which the law is optimal and notes that it reflects an implicit assumption about the statistics of the environment. Adherence to the MML can be used to assess whether the assumption is being made, and analyses of natural stimuli can be used to determine whether the assumption is reasonable. Feed-forward and interactive models subject to a channel separability constraint are consistent with the law.     

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.     

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.     

Making faces: Creating three-dimensional parameterized models of facial expression

Previous studies of the perceptual processing and dynamics of emotional expression in faces have been limited by the lack of realistic yet controlled stimuli. The present work offers researchers a method for creating such stimuli for exploring these phenomena. We describe the creation of the stimuli and a series of experiments testing the validity of these stimuli with respect to emotional expressions in humans. Participants evaluated synthesized facial images and standardized photographs of six basic emotional expressions for intensity and accuracy of perceived emotion. Comparisons of these measures were qualitatively similar for synthesized and photographed faces. A manipulation of the magnitude of the synthesized expressions yielded a significant effect on the perceived intensity of expression. In a subsequent multidimensional scaling study, no systematic differences were uncovered in the derived configurations of the synthesized expressions and the photographs. These results are discussed in the context of possible future research applications.