Eyewitness testimony and memory distortion

Abstract: Do memories change as we acquire new information? Recent research on memory distortion using implicit tests along with research using confidence is reviewed and new studies are presented. Two new studies asked misinformed subjects to provide reasons for their answers. In each study 15% to 27% of subjects said they remembered seeing items they had only read about. In another study subjects were asked to identify the source of misleading items they had seen in slides or read in misleading questions. Subjects were more likely to say they had seen in slides something they read about in the questions than they were to confuse information from two nearly identical sets of slides. Recent work shows that, not only is it possible to distort memory for events, it is possible to implant an entire memory for something that never happened. The evidence is now clear that we can become mentally tricked into making large as well as small changes in the way we recall the past.     

A timing-specific memory distortion effect in young children

It has been suggested that there are systematic distortions in children's memory for temporal durations, such that children's memory is not just less accurate than that of adults but qualitatively different. Experiment 1 replicated the memory distortion effect by demonstrating developmental change in the tendency to confuse a reference duration with one that is shorter rather than longer than it. When the long-term memory demands of the task were reduced by providing reminders of the reference duration on every trial, there were no such qualitative changes in error patterns (Experiment 2). Further evidence for developmental changes in memory distortion was found in the temporal generalization task of Experiment 3, in which stimuli were spaced logarithmically rather than linearly. In Experiment 4, a similar distortion pattern was absent in a task in which children made judgments about the pitch rather than the duration of stimuli, suggesting the effect may be specific to time estimation.     

Immediate and persisting effects of misleading questions and hypnosis on memory reports

Immediate and persisting effects of misleading questions and hypnosis on memory reports were assessed. After listening to a story, 52 highly suggestible students and 59 low and medium suggestible students were asked misleading or neutral questions in or out of hypnosis. All participants were then asked neutral questions without hypnosis. Both hypnosis and misleading questions significantly increased memory errors, and misleading questions produced significantly more errors than did hypnosis. The 2 effects were additive, so that misleading questions in hypnosis produced the greatest number of errors. There were no significant interactions with level of hypnotic suggestibility. Implications of these findings for the per se exclusion of posthypnotic testimony are discussed.     

Effects of suggestibility and hypnosis on accurate and distorted retrieval from memory

Research investigated the hypothesis inferred from the theorizing of Loftus that suggestibility is related to the tendency to incorporate incorrect information into memory when this information has been subtly introduced after the to-be-remembered events have occurred. Specifically, it was predicted that if level of suggestibility is theoretically relevant to subjects' acceptance of misleading information, then more subjects who are highly hypnotically suggestible than those with a low level of hypnotic suggestibility will incorporate the incorrect information into memory. Hypnotic as compared with waking instruction should enhance this distortion effect by providing a context of testing in which subjects are readily prone to respond positively to suggestions. Eight independent groups of 12 subjects were tested. Separate groups of subjects of high and low suggestibility were presented with misleading or neutral information about a wallet-snatching incident and tested for memory under either waking or hypnotic instruction. Analysis of subjects' memory distortions indicated that suggestibility plays a somewhat different role than has been argued previously. The magnitude of distortion that was observed varied according to the stimulus features that were studied, but hypnotic suggestibility was not associated with the distortion effect. Despite the fact that hypnosis did not enhance recall in any way, subjects were frequently confident that distorted memories recovered under hypnosis were accurate.     

Individual differences in misremembering pre-psychotherapy distress: personality and memory distortion

In 2 studies, clients were asked, after terminating psychotherapy, to complete a measure of symptomatic distress exactly as they had in their pre-therapy assessment. Most clients overestimated their pre-therapy distress, which may lead to an illusion of positive change. A 3rd study found no overestimation of previously reported distress in a control sample. The degree of overestimation for psychotherapy clients was positively correlated with anxiety, depression, and neuroticism, and negatively correlated with ego strength, self-deception, and lying. Distress levels at termination mediated these effects of individual differences. Individual differences were also correlated with specific types of recall error, such as adding to, exaggerating, omitting, and minimizing previously reported symptoms. Misremembering prior emotions may both reflect and create individual differences.     

Hypnotizability, preference for an imagic cognitive style, and memory creation in hypnosis

We sought to extend the finding (Laurence & Perry, 1983) that it is possible through hypnosis to create a pseudomemory of a specific event. Subjects were compared on their responses to a hypnotic suggestion. We also examined the relation between nonhypnotic measures (Preference for an Imagic Cognitive Style [PICS] test and the Tellegen Absorption Scale [TAS]) and response to the suggestion. Highly (45.45%) and moderately-highly (46.15%) susceptible subjects believed that the pseudomemory was veridical, but none of the low susceptible subjects did so. Together, hypnotic susceptibility, the PICS, and their interaction more strongly predicted pseudomemory creation than any of these main effects alone. Performance on the TAS was also related to the occurrence of pseudomemory, but this relation was redundant with performance on the other measures. These results point to the complexity of the variables involved in pseudomemory creation during hypnosis.     

Memory on the beach: an Australian memory (and hypnosis) laboratory

The memory (and hypnosis) lab at the University of New South Wales investigates a broad range of memory topics. We try to find innovative methods from cognitive and clinical psychology to address theoretical and empirical questions about memory. We aso use hypnosis as one major methodological tool in our investigations of memory (as well as other cognitive processes). In this paper, we review the projects currently underway in our memory (and hypnosis) lab.     

Investigating the variability of memory distortion for an analogue trauma

In this paper, we examine whether source monitoring (SM) errors might be one mechanism that accounts for traumatic memory distortion. Participants watched a traumatic film with some critical (crux) and non-critical (non-crux) scenes removed. Twenty-four hours later, they completed a memory test. To increase the likelihood participants would notice the film's gaps, we inserted visual static for the length of each missing scene. We then added manipulations designed to affect people's SM behaviour. To encourage systematic SM, before watching the film, we warned half the participants that we had removed some scenes. To encourage heuristic SM some participants also saw labels describing the missing scenes. Adding static highlighting, the missing scenes did not affect false recognition of those missing scenes. However, a warning decreased, while labels increased, participants' false recognition rates. We conclude that manipulations designed to affect SM behaviour also affect the degree of memory distortion in our paradigm.     

Reality monitoring and memory distortion: Effects of negative, arousing content

Although individuals often claim to vividly remember negatively arousing information, few studies have been performed to examine whether this emotional information is remembered more accurately than nonemotional information. In the present study, we investigated whether the emotional content of items modulates the accuracy with which individuals make reality-monitoring decisions. Participants (young adults, 18-35 years of age) distinguished imagined from seen words (Experiments 1 and 3A) or objects (Experiments 2 and 3B). Half of the items studied in each condition (presented and imagined) were negative and arousing, and half were neutral. The participants mistook imagined items for presented ones, but the number of reality-monitoring errors was lower for the arousing items than for the neutral items. Negative, arousing items appear to be remembered with contextual detail more frequently than are neutral items, leading memory for this emotional information to be less prone to distortion than is memory for neutral information. Thus, negative arousal can enhance not only the subjective vividness of a memory, but also a memory's accuracy.     

Exaggeration in memory: Systematic distortion of self-evaluative information under reduced accessibility

The tendency to exaggerate specific information about oneself can stem from reconstructive memory processes that are distinct from motivated self-enhancement or self-presentation. While exaggerations sometimes reflect these motives, they also result from attempts to reconstruct one’s past. Three studies examined test scores as they became less accessible in memory. Study 1 provided a real-world illustration, demonstrating reduced accessibility and increased exaggeration of SAT scores over time. Two experiments utilized test scores randomly assigned in a controlled laboratory setting. Increased exaggeration was observed following distraction (Study 2), and after a one-week delay (Study 3). Distortions in scores reported were consistent with beliefs about the self, rather than uniformly self-serving. Under reduced accessibility, exaggeration was predicted by beliefs about achievement (Study 1) and subjective perceptions of test performance (Study 2). Study 3 manipulated perceived performance. Positive performance feedback caused greater exaggeration under reduced accessibility, whereas negative feedback reduced the tendency to exaggerate.     

The effect of presentation format and encoding strategy on associative memory distortion

IntroductionPrevious studies using semantically related words revealed more accurate memory when the items were encoded visually rather than auditorily and when mental images were created during encoding. However, how the level of memory distortion is affected by the creation of different mental imagery formats or by techniques that should suppress generation of mental images has rarely been investigated.ObjectiveThe aim of the present studies was to investigate the ways in which the encoding strategy affects the accuracy of memory reports for two presentation formats of semantically related words: verbal and pictorial.MethodIn experiment 1, the participants were asked to memorize either pictures or their verbal equivalents (words) from the same category, using one of two encoding strategies: uttering the words or counting backwards. In experiment 2, pictorially or auditory presented material was encoded together with the creation of either visual or auditory mental images of the items. The results of the experimental groups were compared to control groups that received no specific instruction.ResultsHigher levels of false recognition, together with lower rates of correct recognition, were observed for words, presented either visually or auditory, relative to pictures. Moreover, self-generation of additional code during the processing of information favored the reduction of false recognitions.ConclusionEncoding strategies that engaged dual coding reduced false recognition. The results are discussed within the distinctiveness heuristic phenomenon.