Manipulations of List Type in the DRM Paradigm: A Review of How Structural and Conceptual Similarity Affect False Memory

Integrating word-form representations with global similarity computation in recognition memory

In recognition memory, retrieval is thought to occur by computing the global similarity of the probe to each of the studied items. However, to date, very few global similarity models have employed perceptual representations of words despite the fact that false recognition errors for perceptually similar words have consistently been observed. In this work, we integrate representations of letter strings from the reading literature with global similarity models. Specifically, we employed models of absolute letter position (slot codes and overlap models) and relative letter position (closed and open bigrams). Each of the representations was used to construct a global similarity model that made contact with responses and RTs at the individual word level using the linear ballistic accumulator (LBA) model (Brown & Heathcote Cognitive Psychology, 57 , 153-178, 2008). Relative position models were favored in three of the four datasets and parameter estimates suggested additional influence of the initial letters in the words. When semantic representations from the word2vec model were incorporated into the models, results indicated that orthographic representations were almost equally consequential as semantic representations in determining inter-item similarity and false recognition errors, which undermines previous suggestions that long-term memory is primarily driven by semantic representations. The model was able to modestly capture individual word variability in the false alarm rates, but there were limitations in capturing variability in the hit rates that suggest that the underlying representations require extension.

Comparison of semantic and phonological false memories in short- and long-term tests

The Deese-Roediger-McDermott (DRM) paradigm has been at the centre of false memory research. Whereas most work with this paradigm has examined memory at the long term and with semantically associated lists, the present study examines phonological and semantic false memories at both short- and long-term delays. In two experiments, participants studied short lists containing six (Experiment 1) or four (Experiment 2) items, either semantically or phonologically related to the same non-studied critical items (CI). Following each list, participants completed 36 trials of an immediate recognition task (short-term memory [STM]-only condition) only or they also completed a surprise recognition test after a 1-min delay after all 36 STM trials (STM + long-term memory [LTM] condition). In STM, false alarms were higher in phonological lists, whereas after the delay, false alarms were higher in semantic lists, reflecting differential sensitivity to the type of association as a function of delay. A third experiment examined LTM performance after controlling for prior testing and yielded highly similar results. Both the activation-monitoring framework (AMF) and fuzzy-trace theory (FTT) can explain the majority of the findings, with some remaining issues. These results confirm that information from the knowledge base (LTM) does influence accuracy in an STM task, albeit less so than perceptual level similarity.

Investigating the neural basis of schematic false memories by examining schematic and lure pattern similarity

ABSTRACTSchemas allow us to make assumptions about the world based upon previous experiences and aid in memory organisation and retrieval. However, a reliance on schemas may also result in increased false memories to schematically related lures. Prior neuroimaging work has linked schematic processing in memory tasks to activity in prefrontal, visual, and temporal regions. Yet, it is unclear what type of processing in these regions underlies memory errors. The current study examined where schematic lures exhibit greater neural similarity to schematic targets, leading to this memory error, as compared to neural overlap with non-schematic lures, which, like schematic lures, are novel items at retrieval. Results showed that patterns of neural activity in ventromedial prefrontal cortex, medial frontal gyrus, middle temporal gyrus, hippocampus, and occipital cortices exhibited greater neural pattern similarity for schematic targets and schematic lures than between schematic lures and non-schematic lures. As such, results suggest that schematic membership, and not object history, may be more critical to the neural processes underlying memory retrieval in the context of a strong schema.

Modelling orthographic similarity effects in recognition memory reveals support for open bigram representations of letter coding

A variety of letter string representations has been proposed in the reading literature to account for empirically established orthographic similarity effects from masked priming studies. However, these similarity effects have not been explored in episodic memory paradigms and very few memory models have employed orthographic representation of words. In the current work, through two recognition memory experiments employing word and pseudoword stimuli respectively, we empirically established a set of key orthographic similarity effects for the first time in recognition memory - namely the substitution effect, transposition effect and reverse effect in recognition memory of words and pseudowords, and a start-letter importance in recognition memory of words. Subsequently, we compared orthographic representations from the reading literature including slot coding, closed-bigram, open-bigram and the overlap model. Each of these representations was situated in a global matching model and fitted to recognition performance via Luce's choice rule in a hierarchical Bayesian framework. Model selection results showed support for the open-bigram representation in both experiments.

Investigating the neural basis of schematic false memories by examining schematic and lure pattern similarity

Schemas allow us to make assumptions about the world based upon previous experiences and aid in memory organization and retrieval. However, a reliance on schemas may also result in increased false memories to schematically related lures. Prior neuroimaging work has linked schematic processing in memory tasks to activity in prefrontal, visual, and temporal regions. Yet, it is unclear what type of processing in these regions underlies memory errors. The current study examined where schematic lures exhibit greater neural similarity to schematic targets, leading to this memory error, as compared to neural overlap with non-schematic lures, which, like schematic lures, are novel items at retrieval. Results showed that patterns of neural activity in ventromedial prefrontal cortex, medial frontal gyrus, middle temporal gyrus, hippocampus, and occipital cortices exhibited greater neural pattern similarity for schematic targets and schematic lures than between schematic lures and non-schematic lures. As such, results suggest that schematic membership, and not object history, may be more critical to the neural processes underlying memory retrieval in the context of a strong schema.

Misspelled logotypes: the hidden threat to brand identity

Brand names are valuable company assets often accompanied by a unique graphical composition (i.e., as logotypes). Recent research has demonstrated that this uniqueness makes brand names and logotypes susceptible to counterfeiting through misspelling by transposition in tasks that require participants to identify correct spellings. However, our understanding of how brand names are incidentally processed when presented as logotypes is incomplete. To address this gap in knowledge, we conducted a virtual reality experiment to explore the transposed-letter confusability effect on brand name recognition. Participants were immersed in a virtual reality setting and incidentally exposed to logotypes that had correctly spelled brand names or included letter transpositions. Offline analyses revealed that participants were more accurate at recognizing brand names that had been presented with correct spellings than those that had been misspelled. Furthermore, participants exhibited false memories for misspelled logotypes, recalling them as if they had been spelled correctly. Thus, our findings revealed that the incidental processing of misspelled logotypes (e.g., SASMUNG) affects the accuracy of logotype identity recognition, thereby underscoring the challenges faced by individuals when identifying brand names and the elements that make counterfeits so effective.

Hippocampal activity predicts contextual misattribution of false memories

Failure of contextual retrieval can lead to false recall, wherein people retrieve an item or experience that occurred in a different context or did not occur at all. Whereas the hippocampus is thought to play a crucial role in memory retrieval, we lack understanding of how the hippocampus supports retrieval of items related to a target context while disregarding related but irrelevant information. Using direct electrical recordings from the human hippocampus, we investigate the neural process underlying contextual misattribution of false memories. In two large datasets, we characterize key physiological differences between correct and false recalls that emerge immediately prior to vocalization. By differentiating between false recalls that share high or low contextual similarity with the target context, we show that low-frequency activity (6 to 18 Hz) in the hippocampus tracks similarity between the current and retrieved context. Applying multivariate decoding methods, we were able to reliably predict the contextual source of the to-be-recalled item. Our findings elucidate one of the hallmark features of episodic memory: our ability to distinguish between memories that were formed on different occasions.

Context-dependent memory recall in HMD-based immersive virtual environments

The article introduces an original VR-based experiment which explores context-dependent memory recall in humans. It specifically examines the recall of correct and falsely induced semantic memories. With the aid of VR head-mounted displays, 92 students of psychology were placed in a computer-generated indoor virtual environment and asked to memorize the presented lists of words. Afterwards, the participants were placed in the same indoor virtual environment or an alternative outdoor virtual environment and asked to recall the words. The number of correct and falsely induced words was then measured. On average, women recalled significantly more correct words from the list than men, regardless of the environmental context. Despite the assumptions, we did not observe a separate effect of exposure to different environments during learning and recall of material on memory performance. Likewise, we did not detect any effects of the learning context or biological sex in the case of the production of false memories. These results provide a novel insight into previous knowledge regarding the memory processes that occur in virtual environments. Although we failed to confirm the role of context in recalling learned material in general, we found a hint that this context might interact with specific memory processes of biological sexes. However, the design of this study only captured the effect of changing the environment during memory recall and did not address the role of specific context in remembering learning material. Further research is therefore needed to better investigate these phenomena and examine the role of biological sex in context-dependent memory processes.

Lay Definitions of Intelligence, Knowledge, and Memory: Inter- and Independence of Constructs

The present study examined how lay participants define the following concepts used widely in psychology: being intelligent, knowing, and remembering. In the scientific community, knowledge overlaps with the contents of semantic memory, crystallized intelligence reflects the accumulation of knowledge, knowledge and event memory interact, and fluid intelligence and working memory correlate. Naturally, the lay public has implicit theories of these constructs. These theories mainly distinguish between intelligent and unintelligent behaviors and tend to include characteristics outside psychometric studies of intelligence, such as emotional intelligence. Here, we asked lay participants from the online platform Prolific to explain "what does being intelligent mean to you?" as well as "knowing" and "remembering" to understand their degree of alignment with theoretical conceptualizations in the research community. Qualitative coding of participant definitions showed that intelligence and knowledge are closely related, but asymmetrically-when defining what it means to be intelligent, participants reference knowledge, but intelligence is not considered in explaining knowing. Although participants note that intelligence is multi-faceted and related to problem-solving, there is an emphasis (in terms of frequency of mentions) on the crystallized side of intelligence (i.e., knowledge). A deeper understanding of lay participants' mental models of these constructs (i.e., their metacognitions) is essential for bridging gaps between experts and the general public.

Short-Term Phantom Recollection in 8–10-Year-Olds and Young Adults

Illusory conscious experience of the “presentation” of unstudied material, called phantom recollection, occurs at high levels in long-term episodic memory tests and underlies some forms of false memory. We report an experiment examining, for the first time, the presence of phantom recollection in a short-term working memory (WM) task in 8- to 10-year-old children and young adults. Participants studied lists of eight semantically related words and had to recognize them among unpresented distractors semantically related and unrelated to the studied words after a retention interval of a few seconds. Regardless of whether the retention interval was filled with a concurrent task that interfered with WM maintenance, the false recognition rate for related distractors was very high in both age groups, although it was higher in young adults (47%) than children (42%) and rivaled the rate of target acceptance. The conjoint recognition model of fuzzy-trace theory was used to examine memory representations underlying recognition responses. In young adults, phantom recollection underpinned half of the false memories. By contrast, in children, phantom recollection accounted for only 16% of them. These findings suggest that an increase in phantom recollection use may underlie the developmental increase in short-term false memory.

Dynamics of working memory process revealed by independent component analysis in an fMRI study

Human memory is prone to errors in many everyday activities but also when cultivating hobbies such as traveling and/or learning a new language. For instance, while visiting foreign countries, people erroneously recall foreign language words that are meaningless to them. Our research simulated such errors in a modified Deese-Roediger-McDermott paradigm for short-term memory with phonologically related stimuli aimed at uncovering behavioral and neuronal indices of false memory formation with regard to time-of-day, a variable known to influence memory. Fifty-eight participants were tested in a magnetic resonance (MR) scanner twice. The results of an Independent Component Analysis revealed encoding-related activity of the medial visual network preceding correct recognition of positive probes and correct rejection of lure probes. The engagement of this network preceding false alarms was not observed. We also explored if diurnal rhythmicity influences working memory processes. Diurnal differences were seen in the default mode network and the medial visual network with lower deactivation in the evening hours. The GLM results showed greater activation of the right lingual gyrus, part of the visual cortex and the left cerebellum in the evening. The study offers new insight into the mechanisms associated with false memories, suggesting that deficient engagement of the medial visual network during the memorization phase of a task results in short-term memory distortions. The results shed new light on the dynamics of working memory processes by taking into account the effect of time-of-day on memory performance.

Within-category similarity negatively affects associative memory performance in both younger and older adults

Associative memory involves the ability to encode and remember the relationship between individual items. This ability can become diminished when there is a high degree of similarity between stimuli that are being learned. Associative memory errors often stem from the fact that lures include a high degree of item familiarity as well as mnemonic similarity with the original associative episode. The current set of experiments examined how this overlap, in the form of within-category similarity, affects veridical and false retrieval in both younger and older adults. Across three experiments, results suggest that mnemonic overlap between targets and lures is detrimental to the ability to discriminate between highly similar information. Specifically, shared category membership for targets and lures led to increased false associative memories across age groups. These results have implications for scenarios where there is a high degree of overlap between target and lure events and indicate that these types of associative memory distinctions are difficult irrespective of age.

Is there a survival processing effect in metacognition?

Memory systems serve an adaptive function for the fitness of organisms. A good example of this is the Survival Processing Effect (SPE) which points to increased retention of information when it is processed in a survival context compared to other contexts. Survival processing may also affect metacognitive processes, by increasing confidence judgments as well as increasing metacognitive sensitivity. No previous study, however, has directly examined whether processing information for survival also has an effect on metacognitive processes. Here we ask whether SPE extends to the metacognitive system in terms of both metacognitive sensitivity and confidence bias. In Experiment 1 participants were asked to rate a list of words in terms of relevance in a survival scenario or a moving scenario. In a surprise old/new recognition test, they were given one word at a time and asked to indicate if they have rated the presented word before and state how confident they are in that choice. Surprisingly, the results did not reveal a SPE, which may have been due to high overall performance in the recognition task. In Experiment 2 we increased the level of difficulty of the memory task, which resulted in a robust SPE, but could not find this effect in metacognitive monitoring. Together, these results suggest that survival processing may not affect metacognitive processes in a reliable fashion.

False memory confidence depends on the prefrontal reinstatement of true memory

For confidence of memory, a neural basis such as traces of stored memories should be required. However, because false memories have never been stored, the neural basis for false memory confidence remains unclear. Here we monitored the brain activity in participants while they viewed learned or novel objects, subsequently decided whether each presented object was learned and assessed their confidence levels. We found that when novel objects are presented, false memory confidence significantly depends on the shared representations with learned objects in the prefrontal cortex. However, such a tendency was not found in posterior regions including the visual cortex, which may be involved in the processing of perceptual gist. Furthermore, the confidence-dependent shared representations were not observed when participants correctly answered novel objects as non-learned objects. These results demonstrate that false memory confidence is critically based on the reinstatement of high-level semantic gist of stored memories in the prefrontal cortex.

Item-specific encoding reduces false recognition of homograph and implicit mediated critical lures

We evaluated the effects of item-specific and relational encoding instructions on false recognition for critical lures that originated from homograph and mediated study lists. Homograph lists contained list items that were taken from two meanings of the same critical lure (e.g., autumn, trip, harvest, stumble; for fall) which disrupted thematic/gist consistency of the list. Mediated lists contained unrelated list items (e.g., slippery, spicy, vent, sleigh) that were indirectly related to a critical lure (e.g., cold), through a set of non-presented mediators (e.g., wet, hot, air, snow), and had no thematic/gist consistency. In two experiments, item-specific and relational encoding improved correct recognition relative to a read-only control task, but only item-specific encoding reduced false recognition of critical lures. Signal-detection analyses indicated that the item-specific reduction increased test-based monitoring. The item-specific reduction for homograph and mediated critical lures is consistent with the activation-monitoring framework given gist-based processes are reduced or eliminated on these list types.

Transcranial Direct Current Stimulation Over the Right Anterior Temporal Lobe Does Not Modulate False Recognition

Non-invasive transcranial direct current stimulation (tDCS) over the left anterior temporal lobe (ATL) has been shown to cause a reduction in the rate of false memories with semantically related words. Such a reduction seems to be specific to false memories induced by the study of associative lists, but is not observed when the studied lists are categorical in nature. These findings are interpreted as evidence that the left ATL functions as an integration hub that is crucial for the binding of semantic information into coherent representations of concepts. In order to investigate whether the right ATL might also contribute to semantic integration in the processing of verbal associative material, a follow-up tDCS study was conducted with the stimulation at study lateralized on the right ATL. A sample of 75 undergraduate students participated in an experiment in which they studied 8 associative lists and 8 categorical lists. One third of the participants studied all their word lists under anodal stimulation, another third studied under cathodal stimulation and the other third under sham stimulation. Results showed that stimulation of the right ATL by tDCS does not modulate false recognition for either association-related critical words or category-related critical words. These results provide preliminary support to views positing asymmetric connectivity between the anterior temporal lobes and the semantic representational network, and provide evidence for understanding bilateral brain dynamics and the nature of semantically induced memory distortions.

Questioning the Role of Forward Associative Strength in False Memories: Evidence From Deese-Roediger-McDermott Lists With Three Critical Lures

We report an experiment examining the factors that produce false recognition in the Deese-Roediger-McDermott (DRM) paradigm. We selectively manipulated the probability that critical lures produce study items in free association, known as forward associative strength (FAS), while controlling the probability that study items produce critical lures in free association, known as backward associative strength (BAS). Results showed that false recognition of critical lures failed to differ between strong and weak FAS conditions. Follow-up correlational analyses further supported this outcome, showing that FAS was not correlated with false recognition, despite substantial variability in both variables across our stimulus sets. However, these correlational analyses did produce a significant and strong relationship between BAS and false recognition. These results support views that propose false memory is produced by activation spreading from study items to critical lures during encoding, which leads critical lures to be confused with episodically-experienced events.