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1.  Lateral parietal cortex is modulated by amount of recollected verbal information 
Neuroreport  2009;20(14):1295-1299.
In two prior experiments we reported that activity in the left inferior posterior parietal cortex covaried with amount of information recollected. Given that the experimental materials in these two studies were exclusively pictorial, the question arises whether the findings generalize to other classes of recollected content. If, as we have argued, the left inferior parietal cortex supports the representation of recollected content in an amodal manner, then activity in this region should also be modulated by amount recollected when non-pictorial materials are employed. The current study addressed the question whether left inferior posterior parietal cortex is sensitive to amount of information recollected for verbal rather than pictorial information. At study, participants saw a series of word pairs, in each case generating a sentence that incorporated both words. At test, a mixture of old and new individual words were presented in a modified remember/know task. Participants made one response (R2) if they could recollect the test item and its studied pairmate, another response (R1) if they could recollect some information from the study episode but not the pairmate, a third response (K) if the test item was judged to have been studied in the absence of any recollection of study details, or a fourth, New, response. We assumed that trials where old items were given an R2 response were on average associated with recollection of more study information than when old items were given an R1 response. Thus, we operationally defined ‘amount recollected’ as the contrast between these two trial types (i.e., R2 hits > R1 hits). Using a small volume correction procedure, we identified a cluster within the same left inferior posterior parietal region identified as amount-sensitive in our prior study using the same test procedure. Thus, our prior findings generalize to non-pictorial stimulus materials and support the proposal that left inferior posterior parietal cortex plays a generic role in the maintenance or representation of recollected information.
PMCID: PMC2771458  PMID: 19668014
episodic memory; remember-know; recollection
2.  Dissociation of the neural correlates of recognition memory according to familiarity, recollection, and amount of recollected information 
Neuropsychologia  2007;45(10):2216-2225.
The present experiment used fMRI to investigate whether neural correlates of recognition memory behave in a manner consistent with the proposal that recognition decisions are based on a unidimensional memory strength variable. A modified remember/know recognition test was used in which participants could indicate two levels of recollection. Participants were required to indicate whether a test item was new, familiar (known), elicited recollection of general contextual details from the study episode (R1 response), or elicited a specific recollection of the item with which it was paired at study (R2 response). Little evidence could be found to support the view that Remember/Know/New judgments reflect variations along a single strength dimension. Instead, the findings replicated prior research in indicating that the neural correlates of recollection and familiarity can be doubly dissociated. Two recollection-sensitive regions - left lateral inferior parietal and left fusiform cortex - were found to be sensitive to amount of information recollected, as operationalized in the contrast between R2 and R1 responses. It is proposed that these regions may support the representation of recollected information.
PMCID: PMC1933497  PMID: 17449068
memory strength; fMRI; parietal; hippocampus; dual-process; brain imaging
3.  Attention during memory retrieval enhances future remembering 
Memory & cognition  2009;37(7):953-961.
Memory retrieval is a powerful learning event that influences whether an experience will be remembered in the future. Although retrieval can succeed in the presence of distraction, dividing attention during retrieval may reduce the power of remembering as an encoding event. In the present experiments, participants studied pictures of objects under full attention and then engaged in item recognition and source memory retrieval under full or divided attention. Two days later, a second recognition and source recollection test assessed the impact of attention during initial retrieval on long-term retention. On this latter test, performance was superior for items that had been tested initially under full versus divided attention. More importantly, even when items were correctly recognized on the first test, divided attention reduced the likelihood of subsequent recognition on the second test. The same held true for source recollection. Additionally, foils presented during the first test were also less likely to be later recognized if they had been encountered initially under divided attention. These findings demonstrate that attentive retrieval is critical for learning through remembering.
PMCID: PMC2776078  PMID: 19744935
4.  Déjà vu experiences in healthy subjects are unrelated to laboratory tests of recollection and familiarity for word stimuli 
Recent neuropsychological and neuroscientific research suggests that people who experience more déjà vu display characteristic patterns in normal recognition memory. We conducted a large individual differences study (n = 206) to test these predictions using recollection and familiarity parameters recovered from a standard memory task. Participants reported déjà vu frequency and a number of its correlates, and completed a recognition memory task analogous to a Remember-Know procedure. The individual difference measures replicated an established correlation between déjà vu frequency and frequency of travel, and recognition performance showed well-established word frequency and accuracy effects. Contrary to predictions, no relationships were found between déjà vu frequency and recollection or familiarity memory parameters from the recognition test. We suggest that déjà vu in the healthy population reflects a mismatch between errant memory signaling and memory monitoring processes not easily characterized by standard recognition memory task performance.
PMCID: PMC3842028  PMID: 24409159
déjà vu; memory; recognition; recollection; familiarity
5.  Remember and Know Judgments During Recognition in Chronic Schizophrenia 
Schizophrenia research  2007;100(1-3):181-190.
Deficits in learning and memory are among the most robust correlates of schizophrenia. It has been hypothesized that these deficits are in part due to reduced conscious recollection and increased reliance on familiarity assessment as a basis for retrieval. The Remember-Know (R-K) paradigm was administered to 35 patients with chronic schizophrenia and 35 healthy controls. In addition to making “remember” and “know” judgments, the participants were asked to make forced choice recognition judgments with regard to details about the learning episode. Analyses comparing response types showed a significant reduction in “remember” responses and a significant increase in “know” responses in schizophrenia patients relative to controls. Both patients and controls recalled more details of the learning episode for “remember” compared to “know” responses, although, in particular for “remember” responses, patients recalled fewer details compared with controls. Notably, patients recognized fewer inter-item but not intra-item stimulus features compared with controls. These findings suggest deficits in organizing and integrating relational information during the learning episode and/or using relational information for retrieval. A Dual-Process Signal Detection interpretation of these findings suggests that recollection in chronic schizophrenia is significantly reduced, while familiarity is not. Additionally, a unidimensional Signal Detection Theory interpretation suggests that chronic schizophrenia patients show a reduction in memory strength, and an altered criterion on the memory strength distribution for detecting new compared with old stimuli but not for detecting stimuli that are remembered versus familiar. Taken together, these findings are consistent with a deficit in recollection and increased reliance on familiarity in making recognition memory judgments in chronic schizophrenia.
PMCID: PMC2517628  PMID: 17964760
schizophrenia; psychosis; chronic; memory; episodic; recognition; recollection; familiarity; context; remember; know
6.  Familiarity is related to conceptual implicit memory: An examination of individual differences 
Psychonomic bulletin & review  2012;19(6):1154-1164.
Explicit memory is thought to be distinct from implicit memory. However, growing evidence has indicated that explicit familiarity-based recognition memory judgments rely on the same process that supports conceptual implicit memory. We tested this hypothesis by examining individual differences using a paradigm wherein we measured both familiarity and conceptual implicit memory within the same participants. In Experiments 1a and 1b, we examined recognition memory confidence ROCs and remember/know responses, respectively, to estimate recollection and familiarity, and used a free association task to measure conceptual implicit memory. The results demonstrated that, across participants, familiarity, but not recollection, was significantly correlated with conceptual priming. In contrast, in Experiment 2, utilizing a similar paradigm, a comparison of recognition memory ROCs and explicit associative cued-recall performance indicated that cued recall was related to both recollection and familiarity. These results are consistent with models assuming that familiarity-based recognition and conceptual implicit memory rely on similar underlying processes.
PMCID: PMC3518453  PMID: 22833341
Familiarity; Recollection; Implicit memory; Conceptual priming; Associative cued recall
7.  The hippocampus supports both recollection and familiarity when memories are strong 
Recognition memory is thought to consist of two component processes – recollection and familiarity. It has been suggested that the hippocampus supports recollection, while adjacent cortex supports familiarity. However, the qualitative experiences of recollection and familiarity are typically confounded with a quantitative difference in memory strength (recollection > familiarity). Thus, the question remains whether the hippocampus might in fact support familiarity-based memories whenever they are as strong as recollection-based memories. We addressed this problem in a novel way using the Remember/Know procedure where we could explicitly match the confidence and accuracy of Remember and Know decisions. As in earlier studies, recollected items had higher accuracy and confidence than familiar items, and hippocampal activity was higher for recollected items than for familiar items. Furthermore hippocampal activity was similar for familiar items, misses, and correct rejections. When the accuracy and confidence of recollected and familiar items were matched, the findings were dramatically different. Hippocampal activity was now similar for recollected and familiar items. Importantly, hippocampal activity was also greater for familiar items than for misses or correct rejections (as well as for recollected items vs. misses or correct rejections). Our findings suggest that the hippocampus supports both recollection and familiarity when memories are strong.
PMCID: PMC3220416  PMID: 22049412
learning and memory; hippocampus; fMRI; imaging; remember; know
8.  Functional Significance of Retrieval-related Activity in Lateral parietal cortex: Evidence from fMRI and ERPs 
Human brain mapping  2009;30(5):1490-1501.
The present study addressed the question whether neural activity in left lateral parietal cortex is modulated by amount of information recollected. In two experiments (one using fMRI, the other ERPs) subjects first studied pairs of pictures presented for either one or six seconds. They then performed a standard ‘Remember/Know’ recognition memory test in which the old items comprised one of the pictures from each studied pair. In both experiments, a surprise post-test indicated that subjects recollected more details about the study presentation of the items presented for the longer duration. In the fMRI experiment, recollection- and familiarity-based recognition elicited activity in distinct cortical networks. Additionally, recollection-related activity in left inferior parietal cortex was of greater magnitude for test items presented for six seconds than for one second. In the ERP study the ‘left-parietal old/new effect’ – a putative correlate of successful recollection – was likewise modulated by amount of information retrieved. Together, these findings provide further support for dual-process models of recognition memory and add weight to the proposal that retrieval-related activity in left inferior parietal cortex reflects processes supporting the online representation of retrieved episodic information.
PMCID: PMC2670940  PMID: 18649352
episodic memory; recognition memory; remember-know; event-related potential; episodic buffer
9.  Behavioral and neural evidence for masked conceptual priming of recollection 
Previous research has found that masked repetition primes, presented immediately prior to the test item in a recognition memory test, increase the likelihood that participants think that the item was present in a previous study phase, even if it was not. This memory illusion is normally associated with a feeling of familiarity, rather than recollection (e.g., as indexed by Remember/Know judgments), and has been explained in terms of an increased fluency of processing the test item, which, in the absence of awareness of the cause of that fluency (i.e., the masked prime), is attributed instead to prior exposure in the study phase. Recently however, we have found that masked conceptual primes (semantically rather than associatively related to the test item) have the opposite effect of increasing Remember but not Know judgments. This result appears difficult to explain in terms of existing theories of recollection and familiarity. Here we report data from a functional magnetic resonance imaging study using the same design, in which we replicate our previous behavioral findings, and find converging evidence for increased activity following conceptual primes in brain regions associated with recollection. This neural evidence supports an account in terms of “true” recollection (for example, conceptual primes reactivating semantically related information that was generated at encoding), rather than an artifact of the mutually-exclusive nature of the Remember/Know procedure.
PMCID: PMC3690477  PMID: 23026757
Recollection; Familiarity; fMRI; Conceptual priming; Repetition priming
10.  Could masked conceptual primes increase recollection? The subtleties of measuring recollection and familiarity in recognition memory 
Neuropsychologia  2012;50(13):3027-3040.
We begin with a theoretical overview of the concepts of recollection and familiarity, focusing, in the spirit of this special issue, on the important contributions made by Andrew Mayes. In particular, we discuss the issue of when the generation of semantically-related information in response to a retrieval cue might be experienced as recollection rather than familiarity. We then report a series of experiments in which two different types of masked prime, presented immediately prior to the test cue in a recognition memory paradigm, produced opposite effects on Remember vs. Know judgments. More specifically, primes that were conceptually related to the test item increased the incidence of Remember judgments, though only when intermixed with repetition primes (which increased the incidence of Know judgments instead, as in prior studies). One possible explanation—that the fluency of retrieval of item–context associations can be experienced as recollection, even when the source of that fluency is unknown—is counter to conventional views of recollection and familiarity, though it was anticipated by Andrew in his writings nearly two decades ago.
► We review the estimation of recollection and familiarity, inspired by Andrew Mayes. ► In a recognition memory experiment, masked primes were shown before test cue words. ► Repetition primes increased ‘familiar’ responses, both hits and false alarms. ► Conceptual primes increased remember' responses (recollection), for hits only.
PMCID: PMC3500693  PMID: 22898644
Remember/know; Source memory; Context; Episodic; Priming
11.  Repetition priming affects guessing not familiarity 
The claim that recollection and familiarity based memory processes have distinct retrieval mechanisms is based partly on the observation that masked repetition and semantic priming influence estimates of familiarity derived from know responses but have no effect on estimates of recollection derived from remember responses. Close inspection of the experiments on which this claim is based reveal the effect size to be small, potentially the result of a type-2 error, and/or inflated due to participants not having the opportunity to report guesses. This paper re-evaluates these claims by attempting a partial replication of two such Experiments.
In Experiment 1 participants made remember, know, and guess responses following primed and unprimed target words. In Experiment 2 participants made sure, unsure, and guess following primed and unprimed target words.
In Experiment 1 the repetition priming effect occurred only for guess responses and only for unstudied items. In Experiment 2 the priming effect occurred for both unsure and guess responses, but again only for unstudied items.
The data are consistent with the view that remembering and knowing do not correspond to confidence ratings; and suggest that contrary to earlier findings, recollection and familiarity do not differ in retrieval mechanisms. As such the effects of repetition priming on subjective reports of remembering should not be cited as evidence for the distinction between recollection and familiarity based memory processes.
PMCID: PMC1988817  PMID: 17697339
12.  Dissociation of Recollection-Related Neural Activity in Ventral Lateral Parietal Cortex 
Cognitive neuroscience  2012;3(3-4):142-149.
fMRI responses to recognition memory test items in two regions of ventral lateral parietal cortex—the angular gyrus and temporo-parietal junction (TPJ)—are enhanced when recognition is accompanied by recollection. According to the ‘episodic buffer’ hypothesis, ventral parietal recollection effects reflect processes involved in maintaining or representing recollected information. According to the ‘attention to memory’ hypothesis, however, the effects reflect attentional re-orienting to the products of recollection. The present experiment addressed the question whether these operations map on to the angular gyrus and TPJ, respectively. Subjects were scanned during a memory test that required a Remember/Know/New and a source memory judgment, allowing recollected items to be segregated by amount of contextual information recollected. Angular gyrus activity tracked amount of recollected information, whereas activity in the TPJ was enhanced for items endorsed as recollected, but was insensitive to amount of information recollected. Thus, the two regions likely support functionally dissociable processes.
PMCID: PMC3462819  PMID: 23049621
Human episodic memory; fMRI; Lateral parietal cortex; Source memory; Recollection; Confidence
13.  Emotion Enhances the Subjective Feeling of Remembering, Despite Lower Accuracy for Contextual Details 
Emotion (Washington, D.C.)  2011;11(3):10.1037/a0024246.
Emotion strengthens the subjective experience of recollection. However, these vivid and confidently remembered emotional memories may not necessarily be more accurate. We investigated whether the subjective sense of recollection for negative stimuli is coupled with enhanced memory accuracy for contextual details using the remember/know paradigm. Our results indicate a double-dissociation between the subjective feeling of remembering, and the objective memory accuracy for details of negative and neutral scenes. “Remember” judgments were boosted for negative relative to neutral scenes. In contrast, memory for contextual details and associative binding was worse for negative compared to neutral scenes given a “remember” response. These findings show that the enhanced subjective recollective experience for negative stimuli does not reliably indicate greater objective recollection, at least of the details tested, and thus may be driven by a different mechanism than the subjective recollective experience for neutral stimuli.
PMCID: PMC3864593  PMID: 21668106
emotion; memory; subjective sense of remembering; remember/know; confidence
14.  Sex Differences in the Use of Anticipatory Brain Activity to Encode Emotional Events 
Women and men differ in the way they experience emotional events. Previous work has indicated that the impact of an emotional event depends on how it is anticipated. Separately, it has been shown that anticipation affects memory formation. Here, we assessed whether anticipatory brain activity influences the encoding of emotional events into long-term memory and, in addition, how biological sex affects the use of such activity. Electrical brain activity was recorded from the scalps of healthy men and women while they performed an incidental encoding task (indoor/outdoor judgments) on pleasant, unpleasant and neutral pictures. Pictures were preceded by a cue that indicated the valence of the upcoming item. Memory was tested after a 20-min delay with a recognition task incorporating the remember/know procedure. Brain activity before picture onset predicted later memory of an event. Crucially, the role of anticipatory activity depended entirely on the valence of a picture and the sex of an individual. Right-lateralized anticipatory activity selectively influenced the encoding of unpleasant pictures in women, but not in men. These findings indicate that anticipatory processes influence the way in which women encode negative events into memory. The selective use of such activity may indicate that anticipatory activity is one mechanism by which individuals regulate their emotions.
PMCID: PMC3173860  PMID: 21865478
Prestimulus activity; emotion; anticipation; long-term memory; encoding; biological sex
15.  Recollection can be Weak and Familiarity can be Strong 
The Remember/Know procedure is widely used to investigate recollection and familiarity in recognition memory, but almost all of the results obtained using that procedure can be readily accommodated by a unidimensional model based on signal-detection theory. The unidimensional model holds that Remember judgments reflect strong memories (associated with high confidence, high accuracy, and fast reaction times), whereas Know judgments reflect weaker memories (associated with lower confidence, lower accuracy, and slower reaction times). Although this is invariably true on average, a new two-dimensional account (the Continuous Dual-Process model) suggests that Remember judgments made with low confidence should be associated with lower old/new accuracy, but higher source accuracy, than Know judgments made with high confidence. We tested this prediction – and found evidence to support it – using a modified Remember/Know procedure in which participants were first asked to indicate a degree of recollection-based or familiarity-based confidence for each word presented on a recognition test and were then asked to recollect the color (red or blue) and screen location (top or bottom) associated with the word at study. For familiarity-based decisions, old/new accuracy increased with old/new confidence, but source accuracy did not (suggesting that stronger old/new memory was supported by higher degrees of familiarity). For recollection-based decisions, both old/new accuracy and source accuracy increased with old/new confidence (suggesting that stronger old/new memory was supported by higher degrees of recollection). These findings suggest that recollection and familiarity are continuous processes and that participants can indicate which process mainly contributed to their recognition decisions.
PMCID: PMC3345268  PMID: 21967320
16.  Not all repetition is alike: Different benefits of repetition in amnesia and normal memory 
While it is well known that repetition can enhance memory in amnesia, little is known about which forms of repetition are most beneficial. This study compared the effect on recognition memory of repetition of words in the same semantic context and in varied semantic contexts. To gain insight into the mechanisms by which these forms of repetition affect performance, participants were asked to make Remember/Know judgments during recognition. These judgments were used to make inferences about the contribution of recollection and familiarity to performance. For individuals with intact memory, the two forms of repetition were equally beneficial to overall recognition, and were associated with both enhanced Remember and Know responses. However, varied repetition was associated with a higher likelihood of Remember responses than was fixed repetition. The two forms of repetition also conferred equivalent benefits on overall recognition in amnesia, but in both cases, this enhancement was manifest exclusively in enhanced Know responses. We conclude that the repetition of information, and especially repetition in varied contexts, enhances recollection in individuals with intact memory, but exclusively affects familiarity in patients with severe amnesia.
PMCID: PMC2396955  PMID: 18419835
neuropsychology; amnesia; memory disorders; anoxia; encephalitis; Korsakoff syndrome
17.  Aging reduces veridical remembering but increases false remembering: Neuropsychological test correlates of remember–know judgments 
Neuropsychologia  2008;47(11):2164-2173.
In 1985 Tulving introduced the remember–know procedure, whereby subjects are asked to distinguish between memories that involve retrieval of contextual details (remembering) and memories that do not (knowing). Several studies have been reported showing age-related declines in remember hits, which has typically been interpreted as supporting dual-process theories of cognitive aging that align remembering with a recollection process and knowing with a familiarity process. Less attention has been paid to remember false alarms, or their relation to age. We reviewed the literature examining aging and remember/know judgments and show that age-related increases in remember false alarms, i.e., false remembering, are as reliable as age-related decreases in remember hits, i.e., veridical remembering. Moreover, a meta-analysis showed that the age effect size for remember hits and false alarms are similar, and larger than age effects on know hits and false alarms. We also show that the neuropsychological correlates of remember hits and false alarms differ. Neuropsychological tests of medial-temporal lobe functioning were related to remember hits, but tests of frontal-lobe functioning and age were not. By contrast, age and frontal-lobe functioning predicted unique variance in remember false alarms, but MTL functioning did not. We discuss various explanations for these findings and conclude that any comprehensive explanation of recollective experience will need to account for the processes underlying both remember hits and false alarms.
PMCID: PMC3319377  PMID: 19100756
Human memory; Episodic memory; Cognitive aging; Remember–know; Meta-analysis; Frontal functioning; Medial-temporal functioning; Signal detection
18.  Changes in Familiarity and Recollection across the Lifespan: An ERP Perspective 
Brain research  2009;1310C:124-141.
The ability to recognize previous experience depends on two neurocognitive processes, familiarity, fast-acting and relatively automatic, and recollection, slower-acting and more effortful. Familiarity appears to mature relatively early in development and is maintained with aging, whereas recollection shows protracted development and deteriorates with aging. To assess this model, ERP and behavioral data were recorded in children (9-10 years), adolescents (13-14), young (20-30) and older (65-85) adults during a recognition memory task in which the same items were studied and tested over four cycles. Participants decided whether each item was old or new and then whether the decision was associated with (Remember, R) or without (Know, K) contextual detail. Memory sensitivity was greatest in young adults, although all groups showed increases in memory sensitivity and R judgments with repetition. Familiarity-based processes (mid-frontal episodic memory, EM, effect) appeared to be used by adolescents, young and older adults, but apparently not to the same extent by children. Recollection-based processes (parietal EM effect) were recruited by children, adolescents and young adults, but to a much lesser extent by older adults. Repetition enhanced the parietal effect in all but older adults. However, post-hoc analyses indicated that reduced recollective processing was confined to poor-performing older adults. By contrast, children appeared to rely mainly on recollection concordant with their conservative decision criteria across tests. We conclude that episodic-memory development reflects the increasingly flexible and interchangeable use of familiarity and recollection with a breakdown in the latter at older ages, perhaps limited to poor-performing older adults.
PMCID: PMC2812671  PMID: 19914220
ERP episodic memory effect; lifespan; cognitive development; cognitive aging; familiarity; recollection
19.  The Contribution of Familiarity to Associative Memory in Amnesia 
Neuropsychologia  2006;44(10):1859-1865.
In Experiment 1, using the remember/know paradigm with control participants, we compared the contribution of recollection and familiarity to associative recognition for compound stimuli and for unrelated word pairs. It was demonstrated that familiarity makes a greater contribution to associative recognition of compound stimuli than to associative recognition of unrelated word pairs. In Experiment 2, we examined associative recognition memory in medial temporal lobe amnesics, diencephalic amnesics, and control participants for the stimuli employed in Experiment 1. Whereas associative recognition for compounds and unrelated words was nearly identical in control participants, associative recognition was higher for compounds than for unrelated word pairs in amnesic patients. This pattern was observed in the medial temporal amnesic group as well as in the diencephalic amnesic group. These results suggest that associative recognition in amnesia is enhanced to the extent that performance can be supported by study-induced familiarity for the studied pair.
PMCID: PMC1698551  PMID: 16643967
associative memory; recognition; amnesia; recollection; familiarity; hippocampus; medial temporal lobe; diencephalon
20.  The Neural Substrates of Memory Suppression: A fMRI Exploration of Directed Forgetting 
PLoS ONE  2012;7(1):e29905.
The directed forgetting paradigm is frequently used to determine the ability to voluntarily suppress information. However, little is known about brain areas associated with information to forget. The present study used functional magnetic resonance imaging to determine brain activity during the encoding and retrieval phases of an item-method directed forgetting recognition task with neutral verbal material in order to apprehend all processing stages that information to forget and to remember undergoes. We hypothesized that regions supporting few selective processes, namely recollection and familiarity memory processes, working memory, inhibitory and selection processes should be differentially activated during the processing of to-be-remembered and to-be-forgotten items. Successful encoding and retrieval of items to remember engaged the entorhinal cortex, the hippocampus, the anterior medial prefrontal cortex, the left inferior parietal cortex, the posterior cingulate cortex and the precuneus; this set of regions is well known to support deep and associative encoding and retrieval processes in episodic memory. For items to forget, encoding was associated with higher activation in the right middle frontal and posterior parietal cortex, regions known to intervene in attentional control. Items to forget but nevertheless correctly recognized at retrieval yielded activation in the dorsomedial thalamus, associated with familiarity-based memory processes and in the posterior intraparietal sulcus and the anterior cingulate cortex, involved in attentional processes.
PMCID: PMC3253105  PMID: 22238671
21.  Positive and negative remember judgments and ROCs in the plurals paradigm: Evidence for alternative decision strategies 
Memory & cognition  2010;38(5):541-554.
Using old-new ratings and remember-know judgments we explored the plurals paradigm, in which studied words must be distinguished from plurality-changed lures. The paradigm allowed us to investigate negative remembering, that is, the remembering of a plural-altered study item; capacity for this judgment was found to be poorer than or equivalent to the conventional positive remembering. A response-bias manipulation affected positive but not negative remembering. The ratings were used to construct ROC curves and test the prediction of the most common dual-process theory of recognition memory (Yonelinas, 2001) that the amount of recollection can be independently estimated from ROC curves and from remember judgments. By fitting the individual data with pure signal-detection (SDT) models and dual-process models that combined SDT and threshold components (HTSDT), we identified two types of subjects. For those who were better described by HTSDT, the predicted convergence of remember-know and ROC measures was observed. For those who were better described by SDT the ROC intercept could not predict the remember rate. The data are consistent with the idea that all subjects rely on the same representation but base their decisions on different partitions of a decision space.
PMCID: PMC2887610  PMID: 20551335
22.  The contribution of familiarity to recognition memory is a function of test format when using similar foils 
Patient Y.R., who suffered hippocampal damage that disrupted recollection but not familiarity, was impaired on a yes/no (YN) object recognition memory test with similar foils. However, she was not impaired on a forced-choice corresponding (FCC) version of the test that paired targets with corresponding similar foils (Holdstock et al. 2002). This dissociation is explained by the Complementary Learning Systems (CLS) neural-network model (Norman & O'Reilly 2003) if recollection is impaired but familiarity is preserved. The CLS model also predicts that participants relying exclusively on familiarity should be impaired on forced-choice non-corresponding (FCNC) tests, where targets are presented with foils similar to other targets. The present study tests these predictions for all three test formats (YN, FCC, FCNC) in normal participants using two variants of the remember/know procedure. As predicted, performance using familiarity alone was significantly worse than standard recognition on the YN and FCNC tests, but not on the FCC test. Recollection in the form of recall-to-reject was the major process driving YN recognition. This adds support to the interpretation of patient data according to which, hippocampal damage causes a recollection deficit that leads to poor performance on the YN test relative to FCC.
PMCID: PMC3001278  PMID: 19096990
familiarity; recollection; recognition memory; hippocampus; remember/know
23.  Does the Butcher-on-the-Bus Phenomenon Require a Dual-Process Explanation? A Signal Detection Analysis 
The butcher-on-the-bus is a rhetorical device or hypothetical phenomenon that is often used to illustrate how recognition decisions can be based on different memory processes (Mandler, 1980). The phenomenon describes a scenario in which a person is recognized but the recognition is accompanied by a sense of familiarity or knowing characterized by an absence of contextual details such as the person’s identity. We report two recognition memory experiments that use signal detection analyses to determine whether this phenomenon is evidence for a recollection plus familiarity model of recognition or is better explained by a univariate signal detection model. We conclude that there is an interaction between confidence estimates and remember-know judgments which is not explained fully by either single-process signal detection or traditional dual-process models.
PMCID: PMC3383109  PMID: 22745631
episodic memory; recognition; signal detection; context; faces
24.  Directed Forgetting in Post-Traumatic-Stress-Disorder: A Study of Refugee Immigrants in Germany 
People with post-traumatic stress disorder (PTSD) often suffer from memory disturbances. In particular, previous studies suggest that PTSD patients perform atypically on tests of directed forgetting, which may be mediated by an altered emotional appraisal of the presented material. Also, a special role of dissociative symptoms in traumatized individuals’ memory performance has been suggested. Here, we investigate these issues in traumatized immigrants in Germany. In an item-method directed forgetting task, pictures were presented individually, each followed by an instruction to either remember or forget it. Later, recognition memory was tested for all pictures, regardless of initial instruction. Overall, the PTSD group’s discrimination accuracy was lower than the control group’s, as PTSD participants produced fewer hits and more false alarms, but the groups did not differ in directed forgetting itself. Moreover, the more negatively participants evaluated the stimuli, the less they were able to discriminate old from new items. Participants with higher dissociation scores were particularly poor at recognizing to-be-forgotten items. Results confirm PTSD patients’ general discrimination deficits, but provide no evidence for a distinct directed forgetting pattern in PTSD. Furthermore, data indicate that, in general, more negatively perceived items are discriminated with less accuracy than more positively appraised ones. Results are discussed in the larger context of emotion and stress-related modulations of episodic memory, with particular focus on the role of dissociative symptoms.
PMCID: PMC3736047  PMID: 23966914
directed forgetting; post-traumatic stress disorder; emotion; dissociation
25.  Identifying the ERP correlate of a recognition memory search attempt 
Previous recognition memory studies have looked for differences in brain activity during recollection- and familiarity-based responding. Although an ERP component correlated with recollection success has been reported, no analogous component related to search initiation has been found. We argue that such a component has not been discovered because studies have compared trials in which participants have made a search attempt and failed (such as Know responses) with those in which the search attempt is successful (such as Remember responses). In the current study, we compared a task that required judgments of lifetime familiarity (differentiating famous from nonfamous names) with one that required judgments of episodic information (deciding whether a name was seen previously in the experiment). By comparing a task on which familiarity judgments were made with no search attempt to a second task in which a search attempt was likely to occur, we identified a component that may reflect the initiation of a memory search. This effect, maximal between 190 and 235 ms, is correlated with Old judgments in the episodic task. Previous ERP findings (e.g., FN400, parietal old/new effect) were also replicated in the present study.
PMCID: PMC2387216  PMID: 15885990
Recognition memory; Search process; Recollection; Familiarity

Results 1-25 (655812)