Strong memories obscure weak memories in associative recognition

The list strength effect, in which strengthening some memories has a detrimental effect on the retrieval of other memories, has generally not been found in item recognition. The present study shows that the list strength effect does occur in associative recognition. Study materials were sets of overlapping word pairs (A-B, A-C, D-B, etc.). Within critical sets of words, strong pairs were presented three times at study, as compared with one presentation for weak pairs. In Experiment 1, associative recognition for weak pairs was less accurate than that for baseline pairs, and response times for hits were slower. In Experiment 2, receiver-operating characteristic curve data provided further evidence of poor accuracy for weak pairs. These findings support a qualitative distinction between item and associative recognition.     

False memories are hard to inhibit: differential effects of directed forgetting on accurate and false recall in the DRM procedure

Directed forgetting research shows that people can inhibit the retrieval of words that they were previously instructed to forget. The present research applied the directed forgetting procedure to the Deese/Roediger and McDermott (DRM) recall task to determine if directed forgetting instructions have similar or different effects on accurate and false memory. After studying lists of semantically related words, some participants were told to forget those lists, whereas other participants were not. All participants were then shown additional lists to remember. Following study, all participants were asked to free recall as many of the studied words as possible, including those they were previously instructed to forget. Directed forgetting instructions inhibited the accurate recall of studied words, but not the false recall of nonstudied critical words, whether measured by a within-participant or between-participants design. Contrary to an implicit activation hypothesis, false memories survived instructions to forget. These findings were reviewed in terms of fuzzy trace theory and the activation/monitoring approach to false memory.     

Implicitly activated memories are associated to general context cues

Words having more densely entangled associative structures are more likely to be recalled in the presence of related extralist cues. A context-modified PIER2 model predicts that the implicit activation of such structures during study connects them to the context of the learning episode. In two experiments, we evaluated this assumption by varying the associative density of the study words and the accessibility of context information. In Experiment 1, we varied context accessibility by manipulating context awareness and by delaying testing and filling the delay with different types of interfering tasks. In Experiment 2, we varied accessibility by manipulating test delay and type of interference in a factorial design. The effects of associative density were reduced by using implicit testing that never refers to context, by performing interpolated interference tasks, and finally, by extending the length of the delay. Information that is implicitly activated during an episodic experience is associated to the context of that experience.     

Evidence that nonconscious processes are sufficient to produce false memories

Are nonconscious processes sufficient to cause false memories of a nonstudied event? To investigate this issue, we controlled and measured conscious processing in the DRM task, in which studying associates (e.g., bed, rest, awake...) causes false memories of nonstudied associates (e.g., sleep). During the study phase, subjects studied visually masked associates at extremely rapid rates, followed by immediate recall. After this initial phase, nonstudied test words were rapidly presented for perceptual identification, followed by recognition memory judgments. On the perceptual identification task, we found significant priming of nonstudied associates, relative to control words. We also found significant false recognition of these nonstudied associates, even when subjects did not recall this word at study or identify it at test, indicating that nonconscious processes can cause false recognition. These recognition effects were found immediately after studying each list of associates, but not on a delayed test that occurred after the presentation of several intervening lists. Nonconscious processes are sufficient to cause this memory illusion on immediate tests, but may be insufficient for more vivid and lasting false memories.     

Differential effects of electroconvulsive shock on concurrent spatial memories: "old" memories are impaired while "new" memories are spared

The effects of electroconvulsive shock (ECS) on spatial memory first reported by Shavalia, Dodge, and Beatty (1981, Behavioral and Neural Biology, 31, 261-273) were systematically replicated in two experiments. Rats acquired concurrent spatial memories in two 8-arm radial mazes. Each rat was allowed four choices in Maze 1 and then, after 2 h, four choices in Maze 2. After 2 h each rat was tested for retention in Maze 1 and, after 2 more h, was tested for retention in Maze 2. A single ECS was administered immediately after the fourth choice in Maze 2. Retention (as measured by accuracy of Choices 5-8) was diminished for Maze 1 but not for Maze 2. In the second experiment, the delay between the retention tests was eliminated (thus holding the ECS-Choice 5 interval constant for the two mazes). Once again retention of Maze 1 was impaired and retention of Maze 2 was spared; that finding suggests that ECS does not proactively affect radial-arm maze performance. The results of a third experiment converge on the same conclusion; ECS failed to reduce levels of spontaneous alternation. Therefore, ECS appears to interfere retroactively with relatively old spatial memories and newly established memories appear to be immune to the amnestic effects of ECS. Implications and various explanations are considered.     

Creating new memories that are quickly accessed and confidently held

In two experiments involving a total of 542 subjects, a series of slides depicting a burglary was shown. After the initial event, subjects were exposed to one or more narratives about the event that contained some misinformation or neutral information about four critical details. Finally, subjects were tested on their memories of what they saw, and their reaction times and confidence levels were measured. When subjects took a standard test in which the misinformation item was a possible response option, they responded very quickly and confidently when making this incorrect choice. Misled subjects responded as quickly and confidently to these "unreal" memories as they did to their genuine memories. It does not seem, then, that the misinformation effect arises from a large proportion of subjects who must resolve a conflict between two memories when they are tested, a conflict that would be expected to take time. When subjects took a modified test in which the misinformation item was not a possible response, misled subjects were as accurate as were controls, but they responded more slowly, regardless of whether they ultimately chose the right or wrong option. These findings indicate that misinformation does introduce some form of interference not detected by a simple test of accuracy.     

Language is never enough: memories are more than words reveal

In this commentary I discuss the work by Fivush and Schwarzmueller (1998) including some methodological limitations to their study. It is perhaps because of these limitations that the data do not provide support for their linguistic hypothesis concerning the onset of autobiographical memory. The data do, however, address important issues in the study of autobiographical memory, particularly in terms of very long-term retention and reconstruction of unique (and perhaps distinctive) events that are pleasant. This is a welcome change from the typical studies of recall of distinctive life events in which the target event is one that revolves around unpleasant medical procedures. Future research efforts should continue along these lines, although alternative suggestions are made for which theoretical issues need to be addressed and new measures developed. © 1998 John Wiley & Sons, Ltd.     

Verbal overshadowing of visual memories: some things are better left unsaid

It is widely believed that verbal processing generally improves memory performance. However, in a series of six experiments, verbalizing the appearance of previously seen visual stimuli impaired subsequent recognition performance. In Experiment 1, subjects viewed a videotape including a salient individual. Later, some subjects described the individual's face. Subjects who verbalized the face performed less well on a subsequent recognition test than control subjects who did not engage in memory verbalization. The results of Experiment 2 replicated those of Experiment 1 and further clarified the effect of memory verbalization by demonstrating that visualization does not impair face recognition. In Experiments 3 and 4 we explored the hypothesis that memory verbalization impairs memory for stimuli that are difficult to put into words. In Experiment 3 memory impairment followed the verbalization of a different visual stimulus: color. In Experiment 4 marginal memory improvement followed the verbalization of a verbal stimulus: a brief spoken statement. In Experiments 5 and 6 the source of verbally induced memory impairment was explored. The results of Experiment 5 suggested that the impairment does not reflect a temporary verbal set, but rather indicates relatively long-lasting memory interference. Finally, Experiment 6 demonstrated that limiting subjects' time to make recognition decisions alleviates the impairment, suggesting that memory verbalization overshadows but does not eradicate the original visual memory. This collection of results is consistent with a recording interference hypothesis: verbalizing a visual memory may produce a verbally biased memory representation that can interfere with the application of the original visual memory.     

The corrective effects of warning on false memories in the DRM paradigm are limited to full attention conditions

Effects of attention control and forewarning on the activation and monitoring of experimentally induced false memories in the Deese/Roediger-McDermott paradigm were investigated in a young adult sample (N=77). We found that reducing the degree of attention during encoding led to a decrease in veridical recall and an increase in non-presented critical lure intrusions. This effect could not be counteracted by a forewarning instruction. However, these findings did not emerge in a (retrieval supportive) recognition task. It seems that divided attention increases false recall when attention control and forewarning have to compete for limited cognitive resources in a generative free recall as opposed to a retrieval supportive recognition task. Forewarning instructions do not always protect young adults against experimentally induced false memories.     

Olfactory cues are more effective than visual cues in experimentally triggering autobiographical memories

Folk wisdom often refers to odours as potent triggers for autobiographical memory, akin to the Proust phenomenon that describes Proust’s sudden recollection of a childhood memory when tasting a madeleine dipped into tea. Despite an increasing number of empirical studies on the effects of odours on cognition, conclusive evidence is still missing. We set out to examine the effectiveness of childhood and non-childhood odours as retrieval cues for autobiographical memories in a lab experiment. A total of 170 participants were presented with pilot-tested retrieval cues (either odours or images) to recall childhood memories and were then asked to rate the vividness, detail, and emotional intensity of these memories. Results showed that participants indeed reported richer memories when presented with childhood-related odours than childhood-related images or childhood-unrelated odours or images. An exploratory analysis of memory content with Linguistic Inquiry and Word Count did not reveal differences in affective content. The findings of this study support the notion that odours are particularly potent in eliciting rich memories and open up numerous avenues for further exploration.     

Emotional memories are not all created equal: evidence for selective memory enhancement

Human brain imaging studies have shown that greater amygdala activation to emotional relative to neutral events leads to enhanced episodic memory. Other studies have shown that fearful faces also elicit greater amygdala activation relative to neutral faces. To the extent that amygdala recruitment is sufficient to enhance recollection, these separate lines of evidence predict that recognition memory should be greater for fearful relative to neutral faces. Experiment 1 demonstrated enhanced memory for emotionally negative relative to neutral scenes; however, fearful faces were not subject to enhanced recognition across a variety of delays (15 min to 2 wk). Experiment 2 demonstrated that enhanced delayed recognition for emotional scenes was associated with increased sympathetic autonomic arousal, indexed by the galvanic skin response, relative to fearful faces. These results suggest that while amygdala activation may be necessary, it alone is insufficient to enhance episodic memory formation. It is proposed that a sufficient level of systemic arousal is required to alter memory consolidation resulting in enhanced recollection of emotional events.     

Involuntary future projections are as frequent as involuntary memories,but more positive

Mental time travel (MTT) is the ability to mentally project oneself into one’s personal past or future, in terms of memories of past events or projections of possible future events. We investigated the frequency and valence of involuntary (spontaneously arising) MTT in the context of high trait worry. High (N = 18) and low (N = 16) worriers recorded the frequency and valence of involuntary memories and future projections using a structured notebook and completed measures probing individual differences related to negative affectivity. Involuntary future projections were as frequent as involuntary memories. We found a positivity bias for both past and future MTT, in that fewer negative events were reported than positive or neutral ones. This positivity bias was greater for future than for past events. Individual differences related to negative affectivity were positively associated with the proportion of negative events, indicating a reduced positivity bias in individuals with a general tendency to experience negative affect.     

Make-believe memories

Research on memory distortion has shown that postevent suggestion can contaminate what a person remembers. Moreover, suggestion can lead to false memories being injected outright into the minds of people. These findings have implications for police investigation, clinical practice, and other settings in which memory reports are solicited.     

Flashbulb memories

Flashbulb Memories are memories for the circumstances in which one first learned of a very surprising and consequential (or emotionally arousing) event. Hearing the news that President John Kennedy had been shot is the prototype case. Almost everyone can remember, with an almost perceptual clarity, where he was when he heard, what he was doing at the time, who told him, what was the immediate aftermath, how he felt about it, and also one or more totally idiosyncratic and often trivial concomitants. The present paper reports a questionnaire inquiry into the determinants of such memories by asking about other assassinations, highly newsworthy events, and personally significant events. It is shown that while the Kennedy assassination created an extraordinarily powerful and widely shared flashbulb memory, it is not the only event that has created such memories. The principal two determinants appear to be a high level of surprise, a high level of consequentiality, or perhaps emotional arousal (assessed by both rating scales and ethnic group membership). If these two variables do not attain sufficiently high levels, no flashbulb memory occurs. If they do attain high levels, they seem, most directly, to affect the frequency of rehearsal, covert and overt, which, in turn, affects the degree of elaboration in the narrative of the memory that can be elicited experimentally. Parallels are made explicit between the behavioral theory and a less elaborated, speculative neuro-physiological theory of which R. B. Livingston (1967) is the proponent Finally, an argument is made that a permanent memory for incidental concomitants of a surprising and consequential (in the sense of biologically significant) event would have high selection value and so could account for the evolution of an innate base for such a memory mechanism.     

Vivid memories

Fifty-eight undergraduates each recorded their three clearest autobiographical memories and answered questions about them. The resulting 174 memories were almost all rated to be of high personal importance, but low national importance. In contrast to published results of flashbulb memories cued by events which were specific, nationally important, surprising, and consequential, the ratings collected here covered the scales of surprise and consequentiality in a fairly uniform manner. The subjects also answered questions about memories cued by 20 events. For each subject, some of these memories were of ‘flashbulb’ clarity and some were not. The clearer memories were more surprising, consequential, and emotional, indicating that these factors are associated with, though not necessary for, vivid memories.     

False memories

Problems in the context of so-called “false memories” and their topological classification and recommendations for their therapeutic handling are discussed. False memories are defined as constructs, rooted in the “transitional space” and containing partial realities, added fantasies as well as fantasmic transformations of reality. They thus contain a message about the inner state of the patient and a demand to the therapist. Narcissistic monadic forms of false memories are different. These forms serve to support the patient’s narcissistic balance, for example memories of incest, which apparently never took place. Furthermore, phenomena of actively generated false memories are discussed, which mainly arose in the USA, where therapists specialised in recovering incest memories, created them by direct or indirect suggestions in their patients. In many cases then, archaic images occurred, for example memories of having been captured by aliens or about ritual abuse in a sect. The potential psychodynamic background is discussed. These exciting and fascinating scenes form a temptation for the therapist to leave the ground of reality together with the patient and thus give up therapeutic neutrality.     

Memory conformity affects inaccurate memories more than accurate memories

After controlling for initial confidence, inaccurate memories were shown to be more easily distorted than accurate memories. In two experiments groups of participants viewed 50 stimuli and were then presented with these stimuli plus 50 fillers. During this test phase participants reported their confidence that each stimulus was originally shown. This was followed by computer-generated responses from a bogus participant. After being exposed to this response participants again rated the confidence of their memory. The computer-generated responses systematically distorted participants' responses. Memory distortion depended on initial memory confidence, with uncertain memories being more malleable than confident memories. This effect was moderated by whether the participant's memory was initially accurate or inaccurate. Inaccurate memories were more malleable than accurate memories. The data were consistent with a model describing two types of memory (i.e., recollective and non-recollective memories), which differ in how susceptible these memories are to memory distortion.     

Personality characteristics associated with susceptibility to false memories

This study examined whether certain personality characteristics are associated with susceptibility to false memories. Participants first answered questions from the Myers-Briggs Type Indicator in order to measure various personality characteristics. They then watched a video excerpt, the simulated eyewitness event. They were next encouraged to lie about the videotaped event during an interview. A week later, some participants recognized confabulated events as being from the video. Two personality characteristics in particular--the introversion-extroversion and thinking-feeling dimensions--were associated with susceptibility to false memories.