Recognition Memory Task Research Articles

Perceptual Similarity Can Drive Age-Related Elevation of False Recognition.

Older adults consistently show elevated rates of false recognition of new items that are related to studied items. This finding has been largely attributed to a greater tendency for older adults to rely on conceptual gist during memory recognition tasks. However, perceptual factors may also be implicated considering that related items are not only conceptually but also perceptually similar. While some findings do suggest that age-related increases in false recognitions can be driven by perceptual factors, little is known about the nature and circumstances under which these factors operate. To address this gap, we measured basic visual ability as well as false recognition for four different image categories (upright faces, inverted faces, chairs, houses) in younger (n = 34) and older (n = 34) adults. Each image category represented different levels of variability in perceptual similarity and pre-experimental exposure. Perceptual similarity was objectively defined on the basis of the low-level properties of the images. We found evidence that perceptual similarity can contribute to elevated rates of false recognition in older adults. Our results also suggest that declines in basic visual abilities influence elevated false recognition in older adults for perceptually similar but not perceptually dissimilar items. We conclude that both perceptual and conceptual similarity can drive age-related differences in false recognition.

Stronger Functional Connectivity in the Default Mode and Salience Networks Is Associated With Youthful Memory in Superaging.

"Superagers" are older adults who, despite their advanced age, maintain youthful memory. Previous morphometry studies revealed multiple default mode network (DMN) and salience network (SN) regions whose cortical thickness is greater in superagers and correlates with memory performance. In this study, we examined the intrinsic functional connectivity within DMN and SN in 41 young (24.5 ± 3.6 years old) and 40 older adults (66.9 ± 5.5 years old). Superaging was defined as youthful performance on a memory recall task, the California Verbal Learning Test (CVLT). Participants underwent a resting-state functional magnetic resonance imaging (fMRI) scan and performed a separate visual-verbal recognition memory task. As predicted, within both DMN and SN, superagers had stronger connectivity compared with typical older adults and similar connectivity compared with young adults. Superagers also performed similarly to young adults and better than typical older adults on the recognition task, demonstrating youthful episodic memory that generalized across memory tasks. Stronger connectivity within each network independently predicted better performance on both the CVLT and recognition task in older adults. Variation in intrinsic connectivity explained unique variance in memory performance, above and beyond youthful neuroanatomy. These results extend our understanding of the neural basis of superaging as a model of successful aging.

Closing eyes during auditory memory retrieval modulates alpha rhythm but does not alter tau rhythm

The alpha power increase that occurs when the eyes are closed is one of the most well-known effects in human electrophysiology. In particular, previous psychological studies have investigated whether eye closure can boost memory performance under certain circumstances, providing contradictory evidence across sensory input modalities. Although alpha power is modulated during different phases of memory and these modulations are correlated with performance, few studies have reported on the relationship between eye closure, memory, and alpha-band power. The present study investigates the influence of eye closure while participants (n = 21) performed an auditory recognition memory task with spoken words during the recording of magnetoencephalography (MEG) data. Our results showed no evidence for a behavioural effect of eye closure in the performance of the task. In addition, electrophysiological responses to the stimuli showed the expected alpha event-related desynchronization (ERD) 0.5–1 s and a high-alpha/beta event-related synchronization (ERS) 1–2 s after word onset. The data showed the expected memory effect, i.e. remembered words elicited greater 10 Hz ERD than forgotten words in the brain regions typically associated with the language network, suggesting a modulation of tau rhythm. Eye closure modulated alpha rhythm only in posterior-parietal and occipital regions. The lack of interaction and the different localizations found for modulations of tau and classical alpha rhythms suggests that these rhythms play distinct functional roles in memory performance.

Does the implicit outcomes expectancies shape learning and memory processes?

Does the explicit or implicit knowledge about the consequences of our choices shape learning and memory processes? This seems to be the case according to previous studies demonstrating improvements in learning and retention of symbolic relations and in visuospatial recognition memory when each correct choice is reinforced with its own unique and explicit outcome (the differential outcomes procedure, DOP). In the present study, we aim to extend these findings by exploring the impact of the DOP under conditions of non-conscious processing. To test for this, both the outcomes (Experiment 1A) and the sample stimuli (Experiment 1B) were presented under subliminal (non-conscious) and supraliminal conditions in a delayed visual recognition memory task. Results from both experiments showed a better visual recognition memory when participants were trained with the DOP regardless the awareness of the outcomes or even of the stimuli used for training. To our knowledge, this is the first demonstration that the DOP can be effective under unconscious conditions. This finding is discussed in the light of the two-memory systems model developed by Savage and colleagues to explain the beneficial effects observed on learning and memory when differential outcomes are applied.

Temporary inactivation of the medial prefrontal cortex impairs the formation, but not the retrieval of social odor recognition memory in rats.

The hippocampus, medial dorsal thalamus and the perirhinal and entorhinal cortices are essential for visual recognition memory whereas the neural substrates underlying olfactory recognition memories are less well characterized. In the present study we combined chemogenetic inactivation with a social odor recognition memory (SORM) task to test the hypothesis that the medial prefrontal cortex (mPFC) is involved in recognition memory. We demonstrate that temporary chemogenetic inactivation of the mPFC prior to an encoding session impairs social odor recognition memory, whereas silencing the mPFC just prior to the recognition session was without effect. Our data support the critical role of the mPFC in the formation rather than retrieval of social odor memory.

Partitioning the sources of recognition confidence: The role of individual differences

Confidence ratings during old-new recognition memory tasks are thought to index the strength of memory evidence elicited by test probes. However, various subject-specific factors may also influence reported confidence, including perceived self-efficacy and idiosyncratic interpretation of the confidence scale. To measure the contribution of subject-specific variables to confidence ratings, we performed regression analyses on extant data from three recognition experiments encompassing procedural variations in encoding and stimuli, testing the degree to which the person making the judgment (the "subject" factor), versus whether or not the judgment is accurate, influences reported confidence. Overall, confidence was less linked to changes in accuracy, for "new" than for "old" judgments. Critically, the subject factor was at least as predictive of rated confidence as accuracy for "old" judgments, whereas for "new" judgments the subject factor was substantially more predictive of confidence than accuracy. These results suggest that measured confidence is largely a function of who is making the rating, especially when items are identified as "new." This suggests that the utility of confidence in predicting memory accuracy will be limited when stable estimates of subject contributions are unavailable, such as when each subject provides one or a few responses.

Age-Related Decreases in the Retrieval Practice Effect Directly Relate to Changes in Alpha-Beta Oscillations.

The retrieval (or testing) of information leads to better memory performance compared with reencoding. This phenomenon is known as "testing effect" or "retrieval practice effect" and has been primarily described in behavioral studies with healthy young subjects. However, possible age-related changes and their associated underlying neural processes, in particular neural oscillations, remain unclear. To address this issue, we used a previously established paradigm in healthy young (N = 27) and elderly (N = 28) male and female human adults while their brain activity was being recorded using EEG. Subjects viewed prefamiliarized scene images intermixed with new scenes and classified them as indoor versus outdoor (encoding task) or old versus new (retrieval task). Subsequently, subjects performed a recognition memory task 10 min and 24 h after encoding. Behaviorally, both age groups showed the testing effect at both time points but, importantly, it was less pronounced in the elderly. At the neural level, the retrieval compared with the encoding task was accompanied by power decreases in the alpha (9-12 Hz) and beta bands (13-30 Hz), possibly reflecting task demands, and this difference was more pronounced in the elderly. Finally, a correlation analysis revealed that those elderly who displayed a more pronounced testing effect exhibited a neural pattern that was more similar to the younger subjects. These findings provide evidence that the testing effect decreases across the life span, and they suggest that changes in alpha-beta oscillations play a direct role.SIGNIFICANCE STATEMENT Learning new and retrieving old information is part of everyday human life. Understanding how learning processes can be optimized therefore has direct applications in the realm of educational and rehabilitative contexts. Here, we show that retrieval practice is a strategy to optimize encoding into long-term memory in both young and elderly humans. Importantly, retrieval practice was significantly reduced in the elderly and closely related to changes in alpha (9-13 Hz) and beta band (13-30 Hz) oscillations. Our findings suggest that decreased retrieval practice effects across the life span contribute to, and may reflect, age-related declines in memory performance. They further provide new insights into the underlying neural mechanisms and point toward future avenues for neuro-modulatory interventions.

Neural markers of category-based selective working memory in aging

Working memory (WM) is essential for normal cognitive function, but shows marked decline in aging. The importance of selective attention in guiding WM performance is increasingly recognized. Studies so far are inconclusive about the ability to use selective attention during WM in aging. To investigate the neural mechanisms supporting selective attention in WM in aging, we tested a large group of older adults using functional magnetic resonance imaging whilst they performed a category-based (faces/houses) selective-WM task. Older adults were able to use attention to encode targets and suppress distractors to reach high levels of task performance. A subsequent, surprise recognition-memory task showed strong consequences of selective attention. Attended items in the relevant category were recognized significantly better than items in the ignored category. Neural measures also showed reliable markers of selective attention during WM. Purported control regions including the dorsolateral and inferior prefrontal and anterior cingulate cortex were reliably recruited for attention to both categories. Activation levels in category-sensitive visual cortex showed reliable modulation according to attentional demands, and positively correlated with subsequent memory measures of attention and WM span. Psychophysiological interaction analyses showed that activity in category-sensitive areas were coupled with non-sensory cortex known to be involved in cognitive control and memory processing, including regions in the prefrontal cortex and hippocampus. In summary, we found that older adults were able to recruit a network of brain regions involved in top-down attention during selective WM, and individual differences in attentional control corresponded to the degree of attention-related modulation in the brain.

Evidence for the incorporation of temporal duration information in human hippocampal long-term memory sequence representations

There has been much interest in how the hippocampus codes time in support of episodic memory. Notably, while rodent hippocampal neurons, including populations in subfield CA1, have been shown to represent the passage of time in the order of seconds between events, there is limited support for a similar mechanism in humans. Specifically, there is no clear evidence that human hippocampal activity during long-term memory processing is sensitive to temporal duration information that spans seconds. To address this gap, we asked participants to first learn short event sequences that varied in image content and interval durations. During fMRI, participants then completed a recognition memory task, as well as a recall phase in which they were required to mentally replay each sequence in as much detail as possible. We found that individual sequences could be classified using activity patterns in the anterior hippocampus during recognition memory. Critically, successful classification was dependent on the conjunction of event content and temporal structure information (with unsuccessful classification of image content or interval duration alone), and further analyses suggested that the most informative voxels resided in the anterior CA1. Additionally, a classifier trained on anterior CA1 recognition data could successfully identify individual sequences from the mental replay data, suggesting that similar activity patterns supported participants' recognition and recall memory. Our findings complement recent rodent hippocampal research, and provide evidence that long-term sequence memory representations in the human hippocampus can reflect duration information in the order of seconds.

Detecting the neural correlates of episodic memory with mobile EEG: Recollecting objects in the real world

Episodic memory supports recognition of the details of complex real world experiences, providing a continuous record of events embedded within spatial and temporal context. Despite the inherently dynamic nature of real events, the bulk of neuroscientific research to date examines recognition in absence of the detailed contextual information that is known to be a defining characteristic. Given the importance of environmental context for episodic memory, examining ERP correlates of memory in more naturalistic settings is vital for progress in understanding how retrieval operates in daily life. The current study capitalized on recent advances in mobile EEG technology to address this issue and is the first to investigate ERP correlates of episodic retrieval in real world contexts. Participants were guided around a pre-defined route inside a building on campus, while performing a recognition memory task, which paired images of objects with actual physical locations in the building to provide context. Importantly, the findings clearly demonstrate that it is possible to observe reliable neural correlates of memory in real world contexts. Replicating two well established ERP correlates of episodic retrieval reported in prior laboratory based studies, we detected FN400 old/new effects traditionally associated with familiarity between 300 and 500 ms, and a late posterior negativity (LPN) often linked to reconstructive processing or evaluation of retrieval outcomes between 500 and 800 ms. Moreover, the FN400 effect was found to be sensitive to retrieval of context, with more sustained effects for objects encountered in a different context at study and test. Overall, the current work highlights the power of mobile EEG technology for examining complex cognitive functions in more naturalistic real world settings.

Effects of Acute Aerobic Exercise on Cognition and Constructs of Decision-Making in Adults With and Without Hypertension.

Hypertension accelerates brain aging, resulting in cognitive dysfunction with advancing age. Exercise is widely recommended for adults with hypertension to attenuate cognitive dysfunction. Whether acute exercise benefits cognitive function in this at-risk population is unknown. The purpose of this study was to compare the effects of acute aerobic exercise on cognitive function in 30 middle-aged hypertensive (HTN) and 30 age, sex, and body mass index (BMI)-matched non-HTN adults (56 ± 6 years, BMI 28.2 ± 2.9 kg/m2; 32 men). Subjects underwent cognitive testing pre/post 30-min cycling (≈55% peak oxygen consumption). Cognition was assessed using standard metrics of accuracy and reaction time (RT) across memory recognition, 2-back, and Flanker tasks. Behavioral data was further analyzed using drift-diffusion modeling to examine underlying components of decision-making (strength of evidence, caution, bias) and RT (non-decision time). Exercise elicited similar changes in cognitive function in both HTN and non-HTN groups (p > 0.05). Accuracy was unaltered for Flanker and 2-back tasks, while hits and false alarms increased for memory recognition post-exercise (p < 0.05). Modeling results indicated changes in memory hits/false alarms were due to significant changes in stimulus bias post-exercise. RT decreased for Flanker and memory recognition tasks and was driven by reductions in post-exercise non-decision time (p < 0.05). Our data indicate acute exercise resulted in similar, beneficial cognitive responses in both middle-age HTN and non-HTN adults, marked by unaltered task accuracy, and accelerated RT post-exercise. Additionally, drift-diffusion modeling revealed that beneficial acceleration of cognitive processing post-exercise (RT) is driven by changes in non-decision components (encoding/motor response) rather than the decision-making process itself.

Aesthetic Stimuli Attract Visual Spatial Attention

We investigated the relationship between attention and the aesthetic appearance of visual stimuli. In a first study, we evaluated the aesthetic value of pictures depicting chairs by means of a questionnaire. These pictures were categorized as aesthetic, neutral, or non-aesthetic and used in a second study, in which we employed a dot-probe task and a recognition memory task. In the dot-probe task, two pictures of chairs were presented to the left and to the right of fixation, followed by a dot at one of the chair pictures’ positions. Participants decided at which side the dot had been presented. To investigate the relation between the aesthetic value of the chairs and the orientation of attention, we paired either aesthetic or non-aesthetic pictures with neutral pictures. The results showed that participants reacted faster when the dot appeared at the position of the aesthetic chair than when it appeared at the position of the neutral one. Such a ‘congruency’ effect was absent for non-aesthetic chairs. This interactive pattern of results shows that aesthetic stimuli capture attention. In the recognition memory task, in which participants were asked to decide whether a chair had been presented before or not, aesthetic chairs were more accurately and faster recognized than neutral or non-aesthetic ones. Taken together, these results show that aesthetic stimuli entail prioritized cognitive processing. In a final study, we investigated which particular features of the aesthetic stimuli might be important for this effect by correlating the aesthetic evaluation of the pictures with their Gestalt impression.

Saying “yes” when you want to say “no” - pupil dilation reflects evidence accumulation in a visual working memory recognition task

A number of studies have shown that the pupil dilates during stimuli recognition and decision-making. Yet, little is known about the interaction between recognition memory and decision processes. Here, we investigated the possible link between pupil response and decision-related factors during a visual recognition task. Forty-eight volunteers took part in the study. The experimental task was based on the Deese–Roediger–McDermott paradigm designed to study false recognitions. Participants were shown different sets of two meaningless objects. After seeing each set, they were asked to determine whether the subsequent probe (positive, lure or negative) was already presented. We had found that the pupil dilated more and slower, and the reaction time was extended, when the upcoming choice was against individual response bias. Such a result indicates that recognition and rejection in memory tasks could be seen as two behavioral alternatives supported by evidence accumulation, in line with decision-making models. This interpretation was upheld with the drift-diffusion modelling based on pupil data. A similar pattern was observed for errors - larger pupil sizes before incorrect responses were accompanied by longer reaction times. Furthermore, before correct reactions, especially in participants differentiating more accurately between the old and new stimuli, pupil dilation was increasing faster, indicating swifter evidence accumulation. Taking into account the link between cognitive pupillary reflex and norepinephrine release, we conclude that similarly to decision making, reactions in memory tasks may partly depend on the locus coeruleus activity, which is the principal site for norepinephrine synthesis.

Talker-familiarity benefit in non-native recognition memory and word identification: The role of listening conditions and proficiency.

Native listeners benefit from talker familiarity in recognition memory and word identification, especially in adverse listening conditions. The present study addresses the talker familiarity benefit in non-native listening, and the role of listening conditions and listeners' lexical proficiency in the emergence of this benefit. Dutch non-native listeners of English were trained to identify four English talkers over 4 days. Talker familiarity benefit in recognition memory was investigated using a recognition memory task with "old" and "new" words produced by familiar and unfamiliar talkers presented either in the clear or in noise. Talker familiarity benefit in word identification was investigated by comparing non-native listeners' performances on the first and the last day in identifying words in different noise levels, produced by either a trained (included in the voice recognition training) or by an untrained talker (not included in the voice recognition training). Non-native listeners demonstrated a talker familiarity benefit in recognition memory, which was modulated by listening conditions and proficiency in the non-native language. No talker familiarity benefit was found in word identification. These results suggest that, similar to native listening, both linguistic and indexical (talker-specific) information influence non-native speech perception. However, this is dependent on the task and type of speech recognition process involved.

ROC Modelling Data of the Word Frequency Effect: A Formal Model of Visual Word Recognition

This article presents a formal statistical model for assessing the word frequency effect in recognition memory. This topic is relevant because word frequency is the best predictor of performance in recognition memory tasks. Signal Detection Theory was applied using high-frequency and low-frequency words as item-signals. Signal Detection Theory test assumes orthogonality of responses: hits, false alarms, correct rejections, and incorrect rejections. Ninety-six adult male and female students participated in two experiments: one conducted in the laboratory and the other in the class-room. The selected words for memory contained 3 to 5 letters and 1 or 2 syllables to control for length. Significant differences were found between high-frequency and low-frequency words in the number of false alarms for the two experiments. The differences were statistically significant in two experiments. The Cohen effect size was 0.6 and 0.45 respectively. The word frequency effect in first- and second-experiments was F (1, 46) = 4.13, MCE. = 2.34, p = 0.003 and F (1, 46) = 3.71, MCE. = 12.36, p = 0. 01 respectively. A formal model is presented based on the Receiver Operating Characteristic data to assess data trends for high- and low frequency words. Two differentiated models were obtained: a continuous model based on high frequency stimuli and a threshold model based on low frequency stimuli.

SOLID-Similar object and lure image database

Stimulus selection is a critical part of experimental designs in the cognitive sciences. Quantifying and controlling item similarity using a unified scale provides researchers with the tools to eliminate item-dependent effects and improve reproducibility. Here we present a novel Similar Object and Lure Image Database (SOLID) that includes 201 categories of grayscale objects, with approximately 17 exemplars per set. Unlike existing databases, SOLID offers both a large number of stimuli and a considerable range of similarity levels. A common scale of dissimilarity was obtained by using the spatial-arrangement method (Exps. 1a and 1b) as well as a pairwise rating procedure to standardize the distances (Exp. 2). These dissimilarity distances were then validated in a recognition memory task, showing better performance and decreased response times as dissimilarity increased. These methods were used to produce a large stimulus database (3,498 images) with a wide range of comparable similarities, which will be useful for improving experimental control in fields such as memory, perception, and attention. Enabling this degree of control over similarity is critical for high-level studies of memory and cognition, and combining this strength with the option to use it across many trials will allow research questions to be addressed using neuroimaging techniques.

Episodic reconstruction contributes to high-confidence false recognition memories in older adults: Evidence from event-related potentials

Older adults demonstrate greater susceptibility to high-confidence memory distortions. Cognitive processes underlying memory errors in older adults remain unclear. Here, in a categorized pictures paradigm, we used the event-related potential (ERP) to examine the electrophysiological correlates of false recognition. Young and older participants were presented with categorized pictures during study and subsequently completed an old/new recognition memory task that included studied pictures, lure pictures from studied categories, and new pictures. Behavioral results showed proportionally similar but higher-confidence false memories in older adults compared to young adults. ERP results revealed that false recognition elicited a significant early frontal old/new effect indexing familiarity in young adults, while older adults exhibited a reliable late posterior negativity during false recognition. These findings suggest that episodic reconstruction contributes to high-confidence false memories in older adults.

Post-Encoding Amygdala-Visuosensory Coupling Is Associated with Negative Memory Bias in Healthy Young Adults.

The amygdala is well documented as the critical nexus of emotionally enhanced memory, yet its role in the creation of negative memory biases, better memory for negative compared with positive stimuli, has not been clarified. Although prior work suggests valence-specific effects at the moment of "online" encoding and retrieval, with enhanced visuosensory processes supporting negative memories in particular, here we tested the novel hypothesis that the amygdala engages with distant cortical regions after encoding in a manner that predicts inter-individual differences in negative memory biases in humans. Twenty-nine young adults (males and females) were scanned while they incidentally encoded negative, neutral, and positive scenes, each preceded by a line-drawing sketch of the scene. Twenty-four hours later, participants were scanned during an Old/New recognition memory task with only the line-drawings presented as retrieval cues. We replicated and extended our prior work, showing that enhanced online visuosensory recapitulation supports negative memory. Critically, resting-state scans flanked the encoding task, allowing us to show for the first time that individual differences in "off-line" increases in amygdala resting-state functional connectivity (RSFC) immediately following encoding relate to negative and positive memory bias at test. Specifically, post-encoding increases in amygdala RSFC with visuosensory and frontal regions were associated with the degree of negative and positive memory bias, respectively. These findings provide new evidence that valence-specific negative memory biases can be linked to the way that sensory processes are integrated into amygdala-centered emotional memory networks.SIGNIFICANCE STATEMENT Decades of research has placed the amygdala at the center of the emotional memory network. Despite the clinical importance of disproportionate memory for negative compared with positive events, it is not known whether post-encoding increases in amygdala-cortical coupling, possibly reflective of early consolidation processes, bear any influence on the degree or direction of such emotional memory biases. We demonstrate that, across participants, increases in post-encoding amygdala coupling with visuosensory and frontal regions are associated with more pronounced negative and positive memory biases, respectively. These findings provide the first evidence linking post-encoding amygdala modulation to the degree of negative or positive memory bias, emphasizing the need for valence-based accounts of the amygdala's role in emotional memory.

Effects of talker continuity and speech rate on auditory working memory.

Speech processing is slower and less accurate when listeners encounter speech from multiple talkers compared to one continuous talker. However, interference from multiple talkers has been investigated only using immediate speech recognition or long-term memory recognition tasks. These tasks reveal opposite effects of speech processing time on speech recognition - while fast processing of multi-talker speech impedes immediate recognition, it also results in more abstract and less talker-specific long-term memories for speech. Here, we investigated whether and how processing multi-talker speech disrupts working memory maintenance, an intermediate stage between perceptual recognition and long-term memory. In a digit sequence recall task, listeners encoded seven-digit sequences and recalled them after a 5-s delay. Sequences were spoken by either a single talker or multiple talkers at one of three presentation rates (0-, 200-, and 500-ms inter-digit intervals). Listeners' recall was slower and less accurate for sequences spoken by multiple talkers than a single talker. Especially for the fastest presentation rate, listeners were less efficient when recalling sequences spoken by multiple talkers. Our results reveal that talker-specificity effects for speech working memory are most prominent when listeners must rapidly encode speech. These results suggest that, like immediate speech recognition, working memory for speech is susceptible to interference from variability across talkers. While many studies ascribe effects of talker variability to the need to calibrate perception to talker-specific acoustics, these results are also consistent with the idea that a sudden change of talkers disrupts attentional focus, interfering with efficient working-memory processing.

Recovering the variance of d' from hit and false alarm statistics.

Sometimes the reports of primary studies that are potentially analyzable within the signal detection theory framework do not report sample statistics for its main indexes, especially the sample variance of d'. We describe a procedure for estimating the variance of d' from other sample statistics (specifically, the mean and variance of the observed rates of hit and false alarm). The procedure acknowledges that individuals can be heterogeneous in their sensitivity and/or decision criteria, and it does not adopt unjustifiable or needlessly complex assumptions. In two simulation studies reported here, we show that the procedure produces certain biases, but, when used in meta-analysis, it produces very reasonable results. Specifically, the weighted estimate of the mean sensitivity is very accurate, and the coverage of the confidence interval is very close to the nominal confidence level. We applied the procedure to 20 experimental groups or conditions from seven articles (employing recognition memory or attention tasks) that reported statistics for both the hit and false alarm rates, as well as for d'. In most of these studies the assumption of homogeneity was untenable. The variances estimated by our method, based on the hit and false alarm rates, approximate reasonably to the variances in d' reported in those articles. The method is useful for estimating unreported variances of d', so that the associated studies can be retained for meta-analyses.