Implicit false memory in the DRM paradigm: Effects of amnesia, encoding instructions, and encoding duration.

Recent studies with the Deese/Roediger-McDermott (DRM) paradigm have revealed that Korsakoff patients show reduced levels of false recognition and different patterns of false recall compared to controls. The present experiment examined whether this could be attributed to an encoding deficit, or rather to problems with explicitly retrieving thematic information at test. In a variation on the DRM paradigm, both patients and controls were presented with associative as well as categorised word lists, with the order of recall and recognition tests manipulated between-subjects. The results point to an important role for the automatic/controlled retrieval distinction: Korsakoff patients’ false memory was only diminished compared to controls’ when automatic or short-term memory processes could not be used to fulfil the task at hand. Hence, the patients’ explicit retrieval deficit appears to be crucial in explaining past and present data. Results are discussed in terms of fuzzy-trace and activation-monitoring theories.

The present study focuses on both the clinical symptom of confabulation and experimentally induced false memories in patients suffering from Korsakoff's syndrome. Despite the vast amount of case studies of confabulating patients and studies investigating false memories in the Deese-Roediger-McDermott (DRM) paradigm, the nature of Korsakoff patients' confabulatory behaviour and its association with DRM false memories have been rarely examined. Hence, the first aim of the present study was to evaluate confabulatory responses in a large sample of chronic Korsakoff patients and matched controls by means of the Dalla Barba Confabulation Battery. Second, the association between (provoked) confabulation and the patients' DRM false recognition performance was investigated. Korsakoff patients mainly confabulated in response to questions about episodic memory and questions to which the answer was unknown. A positive association was obtained between confabulation and the tendency to accept unstudied distractor words as being old in the DRM paradigm. On the other hand, there was a negative association between confabulation and false recognition of critical lures. The latter could be attributed to the importance of strategic retrieval at delayed memory testing.

Several studies have shown that reliable implicit false memory can be obtained in the DRM paradigm. There has been considerable debate, however, about whether or not conscious activation of critical lures during study is a necessary condition for this. Recent findings have revealed that articulatory suppression prevents subsequent false priming in an anagram task (Lövdén & Johansson, 2003). The present experiment sought to replicate and extend these findings to an implicit word stem completion task, and to additionally investigate the effect of articulatory suppression on explicit false memory. Results showed an inhibitory effect of articulatory suppression on veridical memory, as well as on implicit false memory, whereas the level of explicit false memory was heightened. This suggests that articulatory suppression did not merely eliminate conscious lure activation, but had a more general capacity-delimiting effect. The drop in veridical memory can be attributed to diminished encoding of item-specific information. Superficial encoding also limited the spreading of semantic activation during study, which inhibited later false priming. In addition, the lack of item-specific and phenomenological details caused impaired source monitoring at test, resulting in heightened explicit false memory.

Alcohol impairs explicit memory, whilst leaving implicit memory relatively intact. Less is known about its effects on false memories. The present study examines the effects of alcohol on explicit and implicit false memories using study list repetition as a tool for modulating learning at encoding. Thirty-two participants were given either an alcohol (0.6 g/kg) or placebo beverage before undergoing an encoding phase consisting of 10 lists of nine associated words (veridical items). Each list was associated to a word, which was not presented at encoding (semantically associated non-studied lure; critical item), serving as the measure for false memory. Half of the lists were presented once, and half were repeated three times. The next day, participants underwent an implicit (stem completion and post hoc awareness measurements), and an explicit (free recall) task. Alcohol decreased veridical and false explicit memory for singularly presented lists compared to placebo; no group difference existed for repeated lists. Implicit veridical memory was not affected by alcohol. Awareness memory measures demonstrated in placebo participants an increased ability with repetition in rejecting false memories. The reverse was found in intoxicated participants who with repetition accepted more false memories. Alcohol appears to decrease semantic activation leading to a decline in false memories. Increased learning with repetition, which increases the rejection of false memories under placebo, is reversed under alcohol leading to a decrease in rejection of false memories. The latter effect of alcohol may be due to its ability to impair monitoring processes established at encoding.

Memory is prone to illusions. When people are presented with lists of words associated with a non-presented critical lure, they produce a high level of false recognitions (false memories) for non-presented related stimuli indistinguishable, at the explicit level, from presented words (DRM paradigm). We assessed whether true and false DRM memories can be distinguished at the implicit level by using the autobiographical IAT (aIAT), a novel method based on indirect measures that permits to detect true autobiographical events encoded in the respondent’s mind/brain. In our experiment, after a DRM task participants performed two aIATs: the first aimed at testing implicit memory for presented words (true-memories aIAT) and the second aimed at evaluating implicit memory for critical lures (false-memories aIAT). Specifically, the two aIATs assessed the association of presented words and critical lures with the logical dimension “true.” Results showed that the aIAT detected a greater association of presented words than critical lures with the logical dimension “true.” This result indicates that although true and false DRM memories are indistinguishable at the explicit level a different association of the true and false DRM memories with the logical dimension “true” can be detected at the implicit level, and suggests that the aIAT may be a sensitive instrument to detect differences between true and false DRM memories.

Insight accompanied by an 'aha!' experience has a mnemonic effect. Previous studies of insight have often focused on the mnemonic effect of insight on veridical memories, while the effect of insight on false memories is not known. More understanding of the mnemonic effect of insight on false memories could have implications for the mechanism of insightful mnemonic effects. The present research examined whether insight has a mnemonic effect on false memories. Participants were asked to perform Chinese verbal compound remote associate (CRA) tasks and then complete the Deese-Roediger-McDermott (DRM) task, the critical lure of which was also the solution to the Chinese CRA problem. Compared to non-insight, insight was associated with a lower critical lures rate in Experiment 1 and with lower critical lures and unrelated words rates in Experiment 2 when the presentation of DRM list words was random. Giving a warning before DRM tasks could reduce the critical lures rate of non-insight but had little effect on insightful solutions in Experiment 3. These findings indicate that insight can reduce false memories.

False memories represent distorted memories which are remembered incorrectly or didn’t happen at all in reality. In the present study, the period of time between encoding and testing has been manipulated, in order to explore the effects of delay on implicit and explicit false memories. Two groups of subjects were tested, using the DRM paradigm, for false implicit and explicit memories. One group had no delay period between encoding and test phases, the other group was tested at one week delay after the encoding phase. Results showed no significant differences between implicit and explicit false memories. The delay had significant effect only for true memories, which were significantly lower after one-week delay. Conclusions and future directions of research are discussed. Keywords: False memories, implicit false memories, explicit false memories, true memories, delay

Research on false memory in bilinguals using the DRM task has shown that false memories transfer across languages, but comparisons to within-language conditions have yielded mixed results. In two experiments, Spanish-English bilinguals completed standardized language assessments and a DRM task. Experiment 1 (N = 96) had several study-recall cycles before a final recognition test, and Experiment 2 (N = 72) only tested recognition. Relative to within-language conditions, more critical lures were recalled when the language changed from study to test and when words were studied in mixed-language sequences. With no prior recall test, the rate of critical lure recognition did not differ across language conditions. Language proficiency was not associated with the false-memory effects. Associations of false and veridical memory were negative in recall and positive in recognition. Overall, the findings indicate that proficient bilinguals can integrate information across their languages via a shared semantic network to form false memories.

In this study we report two experiments that investigate the acquisition of affective reactions. In Experiment 1, unfamiliar melodies were played to Korsakoff's syndrome patients and alcoholic and nonalcoholic control subjects who were matched with them according to age and education. Following a retention interval of 5 min, subjects received a preference test on old and new melodies. Korsakoff's syndrome patients showed the same increase in preference for old melodies as a consequence of prior exposures as control subjects did, but their recognition of melodies was significantly impaired in comparison with controls. In Experiment 2, the same subjects saw photographs of two men. Fictional biographical information depicted one as a "good guy" and the other as a "bad guy." After a retention interval of approximately 20 days, Korsakoffs recalled virtually none of the biographical information; however, 78% preferred the good guy, and impression ratings were less favorable for the bad guy. Korsakoff patients developed preferences and impressions even though they did not have voluntary access to the information on which the preferences were based. However, their impression ratings were less extreme than those of controls. The pattern of results of the two studies is discussed in terms of Johnson's (1983) MEM model of memory.

False memories have been extensively investigated over the past few decades using the Deese/Roediger-McDermott (DRM) paradigm. In this paradigm, participants study lists of words associatively related to a non-presented critical lure. During a memory test, these critical lures are falsely recalled or recognized. Most studies have focused on false memories that arise when both encoding and retrieval are conducted in the same language (i.e., within-language conditions), which is typically the participant's native or first language (L1). However, much less is known about false memories when critical lures appear in the memory test in a different language than the studied lists (i.e., between-language conditions), being one of them the participant's second language (L2). The main objective of this exhaustive review was to provide an overview of the current state of research on false recognition using the DRM paradigm in between-language conditions, where languages are switched between encoding and retrieval (i.e., L1L2 versus L2L1). The results revealed a language dominance effect in between-language false memories. In other words, false recognition rates were dependent on the study language, with a trend toward higher false recognition when words were enconded in the L1 (L1L2) compared to when words were encoded in the L2 (L2L1). This review enhances our understanding of how studying words in a first or second language affects false memory in the DRM paradigm, emphasizing the significance of investigating false memory in second language speakers and the necessity for further research in the field.

Test-item sequence affects false memory formation: An event-related potential study

The performance of amnesic Korsakoff patients in delay eyeblink classical conditioning was compared with that of recovered chronic alcoholic subjects and healthy normal control subjects. Normal control subjects exhibited acquisition of conditioned responses (CRs) to a previously neutral, conditioned tone stimulus (CS) following repeated pairings with an unconditioned air-puff stimulus, and demonstrated extinction of CRs when the CS was subsequently presented alone. Both amnesic Korsakoff patients and recovered chronic alcoholic subjects demonstrated an impairment in their ability to acquire CRs. These results indicate that the preservation of delay eyeblink conditioning in amnesia must depend on the underlying neuropathology of the amnesic syndrome. It is known that patients with amnesia caused by medial temporal lobe pathology have preserved conditioning. We have now demonstrated that patients with amnesia caused by Korsakoff's syndrome, as well as recovered chronic alcoholic subjects, have impaired conditioning. This impairment is most likely caused by cerebellar deterioration resulting from years of alcohol abuse.

False memories refer to falsely remembering something that did not happen or that happened differently. The effects of age on episodic memory underlie both the decline in real memories and the increase in false memories. But, what is the richness and what is the feeling of reality of false memories in the elderly? This mini-review on false memory in young and older adults presents the results from the literature using one of the most used paradigms in the laboratory to study false memories - the Deese-Roediger-McDermott paradigm. This paradigm generally consists in the presentation of semantically associated items-lists (words or images) related to a non-presented critical lure (e.g., bed, rest, awake …, the critical lure is sleep). During free recall or recognition tests, the participants regularly produce false memories (intrusions or false recognitions of the critical lures), increasingly with aging. We specifically ask the question of the richness of the false memory trace in young and older adults in terms of contextual associations (What-Where-When-Details binding) and phenomenological characteristics (remembering, knowing, guessing). We propose to examine this issue using a naturalistic episodic memory task via navigation in a virtual environment enriched with series of associated elements (e.g., vegetables stand) linked to non-presented critical lures (e.g., carrots). Based on preliminary results, we propose an integrative model of memory trace which can explain the differences observed between young and old people on the richness of their false memories.

In the Deese-Roediger-McDermott (DRM) paradigm, participants falsely recall or recognize a nonpresented word (critical lure), highly associated with previously studied words. As numerous DRM studies have found a robust false memory effect at the behavioural level, event-related potentials (ERPs) studies have searched for possible overlapping in brain electrical activity between true and false memory. Using the DRM paradigm, the present experiment manipulated the sensory modality of stimulus presentation (auditory vs. visual) in the study phase to analyse the effect of modality match between study and test on true and false recognition. Words were therefore presented either visually or auditorily at study and always visually at test. True recognition was found to be significantly higher in the modality 'match' condition (visual-visual) than in the 'mismatch' condition (auditory-visual), whereas there was no modality-match effect on false recognition of critical lures. A general, overlapping was found between ERP correlates of true and false recognition: FN400 (300-500 ms), left-parietal (400-800 ms) and late right-frontal (1000-1500 ms) old/new effects were similar for both studied words and critical lures. No sensory modality-match effect was associated with FN400 or left-parietal old/new effects. Only the late right-frontal activity was modulated by modality manipulation, with significantly more positive ERPs in the modality-match condition. Sensory modality match of stimulus presentation, therefore, dissociated true and false recognition memory only at the behavioural level but not at the ERP level. Overall, true and false recognition memories seem to share common underlying processes.

Magnetic resonance imaging in alcoholic Korsakoff's syndrome: Evidence for an association with alcoholic dementia