Fluency versus conscious recollection in the word completion performance of amnesic patients

Neural correlates of the Dunning-Kruger effect

The Dunning-Kruger effect (DKE) is a metacognitive phenomenon of illusory superiority in which individuals who perform poorly on a task believe they performed better than others, yet individuals who performed very well believe they under-performed compared to others. This phenomenon has yet to be directly explored in episodic memory, nor explored for physiological correlates or reaction times. We designed a novel method to elicit the DKE via a test of item recognition while electroencephalography (EEG) was recorded. Throughout the task, participants were asked to estimate the percentile in which they performed compared to others. Results revealed participants in the bottom 25th percentile over-estimated their percentile, while participants in the top 75th percentile under-estimated their percentile, exhibiting the classic DKE. Reaction time measures revealed a condition-by-group interaction whereby over-estimators responded faster than under-estimators when estimating being in the top percentile and responded slower when estimating being in the bottom percentile. Between-group EEG differences were evident between over-estimators and under-estimators during Dunning-Kruger responses, which revealed FN400-like effects of familiarity supporting differences for over-estimators, whereas "old-new" memory event-related potential effects revealed a late parietal component associated with recollection-based processing for under-estimators that was not evident for over-estimators. Findings suggest over- and under-estimators use differing cognitive processes when assessing their performance, such that under-estimators may rely on recollection during memory while over-estimators may draw upon excess familiarity when over-estimating their performance. Episodic memory thus appears to play a contributory role in metacognitive judgements of illusory superiority.

Memory Processes in Classification Learning: An Investigation of Amnesic Performance in Categorization of Dot Patterns and Artistic Styles

The role of conscious memory retrieval in category learning was investigated, using amnesic patients and matched control subjects on two classification tasks. Subjects attempted to learn to categorize both dot patterns and the paintings of three Italian Renaissance artists. The amnesic patients were capable of normal classification performance on the dot-pattern stimuli, but were severely impaired at learning to categorize the paintings. On tests of recognition of the classification stimuli, the control subjects were very accurate on the paintings, and only moderately accurate on the dot patterns; the amnesic patients were poorer than the control subjects on both item types, though they were above chance in their recognition of the paintings. These data suggest that amnesic patients are capable of simple, perceptually based category learning, but that richer, more complex stimuli may demand memory retrieval processes that they lack.

Category cued recall evokes a generate-recognize retrieval process

The experiments reported here were designed to replicate and extend McCabe, Roediger, and Karpicke's (2011) finding that retrieval in category cued recall involves both controlled and automatic processes. The extension entailed identifying whether distinctive encoding affected 1 or both of these 2 processes. The first experiment successfully replicated McCabe et al., but the second, which added a critical baseline condition, produced data inconsistent with a 2 independent process model of recall. The third experiment provided evidence that retrieval in category cued recall reflects a generate-recognize strategy, with the effect of distinctive processing being localized to recognition. Overall, the data suggest that category cued recall evokes a generate-recognize retrieval strategy and that the subprocesses underlying this strategy can be dissociated as a function of distinctive versus relational encoding processes.

A critical role of the human hippocampus in an electrophysiological measure of implicit memory

The hippocampus has traditionally been thought to be critical for conscious explicit memory but not necessary for unconscious implicit memory processing. In a recent study of a group of mild amnesia patients with evidence of MTL damage limited to the hippocampus, subjects were tested on a direct test of item recognition confidence while electroencephalogram (EEG) was acquired, and revealed intact measures of explicit memory from 400 to 600 ms (mid-frontal old-new effect, FN400). The current investigation re-analyzed this data to study event-related potentials (ERPs) of implicit memory, using a recently developed procedure that eliminated declarative memory differences. Prior ERP findings from this technique were first replicated in two independent matched control groups, which exhibited reliable implicit memory effects in posterior scalp regions from 400 to 600 ms, which were topographically dissociated from the explicit memory effects of familiarity. However, patients were found to be dramatically impaired in implicit memory effects relative to control subjects, as quantified by a reliable condition × group interaction. Several control analyses were conducted to consider alternative factors that could account for the results, including outliers, sample size, age, or contamination by explicit memory, and each of these factors was systematically ruled out. Results suggest that the hippocampus plays a fundamental role in aspects of memory processing that are beyond conscious awareness. The current findings therefore indicate that both memory systems of implicit and explicit memory may rely upon the same neural structures - but function in different physiological ways.

An investigation of implicit memory through left temporal lobectomy for epilepsy

Temporal lobe epilepsy patients have demonstrated a relative preservation in the integrity of implicit memory procedures. We examined performance in a verbal implicit and explicit memory task in left anterior temporal lobectomy patients (LATL) and healthy normal controls (NCs) while undergoing fMRI. We hypothesized that despite the relative integrity of implicit memory in both the LATL patients and normal controls, the two groups would show distinct functional neuroanatomic profiles during implicit memory. LATLs and NCs performed Jacoby's Process Dissociation Process (PDP) procedure during fMRI, requiring completion of word stems based on the previously studied words or new/unseen words. Measures of automaticity and recollection provided uncontaminated indices of implicit and explicit memory, respectively. The behavioral data showed that in the face of temporal lobe pathology implicit memory can be carried out, suggesting implicit verbal memory retrieval is non-mesial temporal in nature. Compared to NCs, the LATL patients showed reliable activation, not deactivation, during implicit (automatic) responding. The regions mediating this response were cortical (left medial frontal and precuneus) and striatal. The active regions in LATL patients have the capacity to implement associative, conditioned responses that might otherwise be carried out by a healthy temporal lobe, suggesting this represented a compensatory activity. Because the precuneus has also been implicated in explicit memory, the data suggests this structure may have a highly flexible functionality, capable of supporting implementation of either explicit memory, or automatic processes such as implicit memory retrieval. Our data suggest that a healthy mesial/anterior temporal lobe may be needed for generating the posterior deactivation perceptual priming response seen in normals.

Implicit memory in Korsakoff's syndrome: a review of procedural learning and priming studies

Korsakoff's syndrome (KS) is characterized by dense anterograde amnesia resulting from damage to the diencephalon region, typically resulting from chronic alcohol abuse and thiamine deficiency. This review assesses the integrity of the implicit memory system in KS, focusing on studies of procedural learning and priming. KS patients are impaired on several measures of procedural memory, most likely due to impairment in cognitive functions associated with alcohol-related neural damage outside of the diencephalon. The pattern of performance on tasks of implicit priming suggests reliance on a residual, non-flexible memory operating more or less in an automatic fashion. Our review concludes that whether measures of implicit memory reveal intact or impaired performance in individuals with KS depends heavily on specific task parameters and demands, including timing between stimuli, the specific nature of the stimuli used in a task, and the integrity of supportive cognitive functions necessary for performance.

Automatic memory processes in normal ageing and Alzheimer's disease

This study examined the contribution of automatic and controlled uses of memory to stem completion in young, middle-aged and older adults, and compared these data with a study involving patients with Alzheimer's disease (AD) who performed the same task (Hudson and Robertson, 2007). In an inclusion task participants aimed to complete three-letter word stems with a previously studied word, in an exclusion task the aim was to avoid using studied words to complete stems. Performances under inclusion and exclusion conditions were contrasted to obtain estimates of controlled and automatic memory processes using process-dissociation calculations (Jacoby, 1991). An age-related decline, evident from middle age was observed for the estimate of controlled processing, whereas the estimate of automatic processing remained invariant across the age groups. This pattern stands in contrast to what is observed in AD, where both controlled and automatic processes have been shown to be impaired. Therefore, the impairment in memory processing on stem completion that is found in AD is qualitatively different from that observed in normal ageing.

The use of indirect and opposition tests to detect simulated amnesia

Two experiments investigated the effect of instruction to simulate memory impairment on performance on a word stem completion task. In addition to the standard control group, a second control group (divided-attention group) studied the target words concurrently with a digit-monitoring task. Experiment 1, using the indirect instruction, did not discriminate clearly between the groups. Experiment 2 used the opposition instruction in which participants were required to complete stems with words they had not seen earlier. It showed that simulators and controls withheld significantly more studied target items than did the divided-attention group. Increasing the number of study list presentations further increased the difference between the performance of the simulating and control groups and the divided-attention group. These results suggest that the opposition method may be useful in detecting feigned memory impairment.

Automatic and Controlled Uses of Memory in Alzheimer's Disease

This study used the process-dissociation procedure (Jacoby, 1991) to examine the contribution of automatic and controlled uses of memory to a stem completion task in 16 patients with Alzheimer's disease (AD) and a matched group of healthy elderly subjects (EC). In an inclusion task subjects attempted to use a studied word to complete three-letter word stems, in an exclusion task they were instructed to complete stems with unstudied words. Relative to patients with AD, EC subjects produced more target word completions under inclusion conditions, and less target word completions under exclusion conditions. The probability of the AD group using studied words to complete stems was invariant across inclusion and exclusion conditions. Estimates derived from the process-dissociation calculations, showed that the performance of the AD patients was mediated entirely by automatic uses of memory, whereas for EC subjects controlled and automatic processes codetermined task performance. Both estimates of controlled and to a lesser extent automatic uses of memory were greater for the EC than the AD subjects, indicating that the stem completion impairment in AD may not be entirely attributable to a deficiency in controlled memory processes but also due to reduced automatic processing.

Memory and the Korsakoff syndrome: not remembering what is remembered

Following the distinction between involuntary unconscious memory, involuntary conscious memory, and intentional retrieval, the focus of the present paper is whether there is an impairment of involuntary conscious memory among Korsakoff patients. At study, participants generated associations versus counted the number of letters with enclosed spaces or the number of vowels in the target words (semantic versus perceptual processing). In the Direct tests, stems were to be used to retrieve the targets with either guessing or no guessing allowed; in the Opposition tests, the stems were to be completed with the first word that came to mind but using another word if that first word was a target word; and in the Indirect tests, no reference was made to the target words from the study phase. In the Direct tests, the performance of Korsakoff patients was not necessarily worse than the one of healthy controls, provided guessing was allowed. More critical for the Korsakoff patients was the deficient involuntary conscious memory. The deficiency explained the suppression failures in the Opposition tests, the absence of performance differences between the Indirect and Opposition tests, the absence of a beneficial effect in providing information about the status of the stem, the performance boost when allowed to guess, and the very low rate of "Know"/"Remember" responses.

Mis-attribution errors in Alzheimer's disease: the illusory truth effect

Patients with mild Alzheimer's disease (AD) and age-matched controls were compared on a series of tasks designed to measure errors of mis-attribution, the act of attributing a memory or idea to an incorrect source. Mis-attribution was indexed through the illusory truth effect, the tendency for participants to judge previously encountered information to be true. Cognitive theories have suggested that the illusory truth effect reflects the mis-attribution of experimentally produced familiarity (a nonspecific sense that an item has been previously encountered) to the veracity of previously encountered information. Consistent with earlier suggestions that AD impairs both familiarity and recollection (specific memory for contextual details of the study episode), AD patients demonstrated significantly fewer mis-attribution errors under conditions in which the illusory truth effect is thought to rely on relative familiarity (uncued condition), but more mis-attribution errors under conditions thought to rely on relative amounts of contextual recollection (cued condition). These results help further specify the precise nature of memory impairments in AD.

A dissociation between implicit and explicit verbal memory in left temporal lobe epilepsy

PURPOSE

Temporal lobe epilepsy patients are well known to present deficits on explicit verbal memory procedures (e.g., recall, recognition). The integrity of implicit memory procedures in these patients is not established. Previous studies in this area used implicit memory measures contaminated by the effects of explicit memory.

METHODS

We examined the integrity of verbal implicit and explicit memory in left temporal lobe epilepsy (LTLE) patients and hypothesized that a clear dissociation in performance would be found with a relative preservation of implicit memory. TLE patients (n = 15) and age- and education-matched healthy normal patients (n = 15) were shown a 40-word study list, followed by a test phase requiring completion of word stems based on the study words or new/unseen words. Experimental conditions involved instructions to provide either the old (study) words or novel/nonlist words when completing the stem. Measures of automaticity and recollection provided uncontaminated indices of implicit and explicit memory, respectively.

RESULTS

The data showed a significant difference (p < 0.001) between the patients (Recollection, 0.12; SD, 0.18) and controls (0.50, SD, 0.15) on the measure of explicit memory. In contrast, the patients (Automaticity, 0.51; SD, 0.11) and controls (0.45, SD, 0.18) performed similarly on the implicit memory measure, with patient scores clearly at normative levels based on other Process Dissociation Procedure data.

CONCLUSIONS

The data demonstrate the integrity of implicit memory in LTLE patients. Finding a dissociation between the two forms of verbal memory in LTLE patients provides evidence that they rely on different neuroanatomic systems.

Part-list cuing in amnesic patients: evidence for a retrieval deficit

Part-list cuing--the detrimental effect of the presentation of a subset of learned items on recall of the remaining items--was examined in amnesic patients and healthy control subjects. Subjects studied two types of categorized item lists: lists in which each category consisted of strong and moderate items and lists in which each category consisted of weak and moderate items. The subjects recalled a category's strong and weak items in either the presence of or absence of the moderate items serving as retrieval cues. In healthy subjects, part-list cuing impaired recall of the strong items but not of the weak items; in amnesics, part-list cuing impaired recall of both types of items. Part-list cuing is often attributed to a change in the retrieval process from a more effective one when cues are absent to a less effective one when they are present. On the basis of this view, our results indicate that part-list cuing causes a stronger retrieval inefficiency in amnesic patients than in healthy people.

The relationship between recall and recognition in amnesia: effects of matching recognition between patients with amnesia and controls

To examine the relationship between recall and recognition memory in amnesia, the authors conducted 2 experiments in which recognition memory was equated between patients with amnesia and control participants. It was then determined whether recall was also similar across groups. In Experiment 1, recognition was equated by providing amnesic patients with additional study exposures; in Experiment 2, recognition was equated by testing controls following a longer delay. These different methods of equating recognition across groups led to divergent results because amnesic patients' recall performance was lower than controls' recall performance in Experiment 1 but not in Experiment 2. These findings are accounted for by considering the differential contribution of recollection and familiarity to the performance of amnesic patients and controls in the 2 experiments.

Memory dissociation and metamemory in multiple sclerosis

A previous study by Scarrabelotti and Carroll [60] was the first to use Jacoby's process dissociation procedure [31] with an MS group to investigate memory function, and the first to obtain metamemory judgments about recall under inclusion and exclusion instructions. Twelve months later using different words, 49 MS and 39 matched controls were readministered a word stem completion task, and made metamemory judgments about their performance. The California Verbal Learning Test (CVLT) [18], Stroop [64], and Reitan's Word Finding Test (WFT) [57], tests considered to particularly rely on conscious processing, were also readministered. At year one testing no group differences were identified in word stem completion under indirect, inclusion, or exclusion instructions, nor in conscious and automatic estimates. By contrast in year two, MS subjects remembered significantly fewer words under inclusion, and employed significantly less conscious processing than the control group to achieve remembering. However, estimates of automatic memory processing were the same for both groups. MS subjects equalled controls in the prospective and retrospective monitoring of words they consciously recalled under inclusion instructions, in both years. By contrast, each group was poor at monitoring words completed automatically under exclusion instructions; and by year two, MS subjects were even less able to monitor such material than controls. Finally by the second year, reduced conscious processing was also related to reduced performance on the Stroop, WFT, and CVLT recall and use of semantic clustering. Taken together, these findings indicate that automatic memory processing is intact in MS, but impairment in memory, metamemory, and other cognitive tasks becomes evident over time when they rely on conscious processes.

Fluency versus conscious recollection in category-production performance: the performance of schizophrenic patients

The purpose of this study was to investigate the relative contribution in schizophrenics of automatic processes (fluency) and conscious processes (conscious recollection) for the control of preencoded material in category production tasks. In one condition (Exclusion condition), subjects were told specifically not to produce previously presented words during the category-production task. This condition was compared with a standard category-production task in which subjects were told to produce the six first words that came to mind for a semantic category (Inclusion condition). In the inclusion condition, the effects of conscious control and automatic processes operated in the same direction, whereas in the exclusion condition automatic influences and conscious control were opposed. A recognition task followed the category-production tasks. Since the exclusion condition required conscious control of encoded items, we hypothesized that schizophrenic patients would be less able than control subjects to avoid producing study list items. These results indicated that schizophrenics' performance differed from these of control subjects in the exclusion condition but not in inclusion condition. Recognition performance was similar in both the schizophrenic and the control groups. These results suggest a defective conscious control in schizophrenic patients and confirm the data from the literature on explicit memory in these patients.

Awareness of remembering achieved through automatic and conscious processes in multiple sclerosis

Fifty multiple sclerosis (MS) and forty-one matched control subjects were administered a word stem completion task and the California Verbal Learning. Test (CVLT). As predicted, priming in a conventional "implicit" task did not differ for MS and control groups, and under "explicit" instructions verbal list recall was significantly lower in the MS group with recognition intact. Application of the process dissociation procedure (Jacoby, Toth, & Yonelinas, 1993) to the word stem task demonstrated that conscious and unconscious processes both contribute to remembering in MS. Exploratory analyses found no group differences in words remembered under inclusion nor exclusion conditions, though preliminary estimates for MS automatic processing exceeded those for controls. As predicted, prospective metamemory judgments reflected subsequent performance for both groups in the inclusion but not the exclusion condition. By contrast, retrospective monitoring for both groups reflected memory performance in both conditions. However post hoc analyses demonstrated that those MS subjects who employed more automatic processing were less aware retrospectively of their successful remembering under exclusion than MS subjects who used less automatic processing.

Neuropsychological dissociation between recognition familiarity and perceptual priming in visual long-term memory

The present study examined whether the same brain region mediates visual-perceptual repetition priming and a familiarity component of visual recognition memory. In two experiments, familiarity-based recognition was measured in an individual (M.S.) with impaired visual repetition priming due to a lesion of right occipital cortex. In both experiments, M.S. demonstrated intact recognition familiarity despite his visual nondeclarative memory impairment. These results converge with other behavioral results to indicate that recognition familiarity does not depend on the same memory system that mediates perceptual priming.

Controlled and automatic memory process in Alzheimer's disease

The aim of this study was to examine the contribution of controlled (or conscious) and automatic (or unconscious) memory processes to the performance of a stem-completion recall task by persons with Alzheimer's disease and a matched group of healthy elderly individuals. The recall task made use of the process dissociation procedure of Jacoby (1991), which allows the separate estimation of conscious and unconscious influences on memory. Recollection was found to be severely impaired in the community dwelling demented patients. Further, the estimates of the automatic processing were also found to be reduced, although there was considerable overlap in the performance of the two groups on this parameter. It was found that the residual capacity of Alzheimer's patients to recall previously learned information was supported to a substantial degree by their automatic memory processes.

Automatic influences of memory in Alzheimer's disease

Automatic and controlled influences of memory were examined in 12 patients with early Alzheimer's disease (AD) and 12 control subjects. The subjects studied a list of words and then received three-letter word stems in three different retrieval tasks. In an indirect memory task (word-stem completion priming), they were asked to produce the first word that came to mind in response to each stem. In an inclusion task, they were required to produce a studied word in response to each stem, and in an exclusion task they were asked to produce a new, unstudied word for each stem. The performance of the subjects with AD was equal in the inclusion and exclusion conditions, showing no evidence of controlled recollection for the studied words, while their automatic memory as well as priming were preserved. The results provide neuropsychological support for the distinction between controlled and automatic memory processes.

Unconscious influences on amnesics' word-stem completion

Amnesic patients and control subjects were asked to complete three-letter word-stems under one of three retrieval conditions. In a direct condition, they were told to use the stems as retrieval cues for words that had just been presented in a study list. In an indirect condition, they were told to use the first word that came to mind with no reference made to the study list. Finally, in an oppositional condition, they were told to use the first word that came to mind unless it had appeared on the study list. During the study list presentation, the patients and controls had analyzed each word according to either semantic (associating to each word) or graphemic (counting letters with enclosed spaces) instructions. The results revealed that the control subjects produced a different number of study words during retrieval as a function of retrieval instructions and encoding condition. The amnesics, however, did not vary their performance as a function of retrieval instructions. Under all conditions, they completed the word-stems far more frequently with words from the study list than would be expected by chance and they consistently produced more semantic than graphemic responses. We concluded that semantic analysis might affect the fluency with which an item occurs for the amnesic, but that the item itself remains independent of the source of that fluency for these patients. Thus, the level of analysis performed on a word during study can affect the unconscious performance of amnesic patients but is unavailable for use during conscious retrieval.

A positive approach to viewing processing deficit theories of amnesia

This reply is admittedly a defence of the encoding-deficits theory of amnesia. However, it attempts to go further by proposing that this deficit, which was originally designed just to explain amnesics' explicit episodic memory disorder, might be viewed as being but one instance of a more general disorder characteristic of all aspects of amnesic patients' information processing. It is proposed that amnesic patients' inability to perform more consciously controlled conceptual analyses results not only in explicit recall deficits, but sometimes also in instances of below normal implicit memory and recognition ability. Their ability to perform automatic, perceptual-level processing produces normal performance on some implicit and some recognition tasks, but it is not sufficient for all tasks.

Parkinson's disease affects automatic and spares intentional verbal learning. A stochastic approach to explicit learning processes

We studied word list and paired associates learning in patients with idiopathic Parkinson's disease and normal controls by means of a two-stage stochastic model, which allows independent measurements of encoding, storage and retrieval abilities. We preliminarily ascertained that the model components were both sufficient and necessary to account for the overall performance of the subjects, and then compared the learning abilities between the two groups. Parkinson's disease patients were selectively impaired in identifying well-known engrams, for which learning is superfluous, and in automatic retrieval, namely in abilities that do not need attentional effort. By contrast, they were unimpaired in encoding and intentional retrieval, which require a purposeful effort. The automatic-voluntary dissociation of Parkinson's disease patients' motor behaviour is, therefore, paralleled by some features of their memory performance.

The word frequency effect in recognition memory versus repetition priming

The role of word frequency in recognition memory and repetition priming was investigated by using a manipulation of attention. In Experiment 1, the lexical decision task produced greater repetition priming for low-frequency words than for high-frequency words following either the attended or the unattended study condition. The recognition memory test, on the other hand, showed a low-frequency word advantage only following the attended study condition. Furthermore, this advantage was limited to the measure of recognition memory based on conscious recollection of the study episode. In Experiment 2, a speeded recognition memory test replicated the pattern obtained with the unspeeded recognition memory test in Experiment 1. These results argue against the view that the word frequency effects in recognition memory and repetition priming have the same origin. Instead, the results suggest that the word frequency effect in recognition memory has its locus in conscious recollection.

Involuntary conscious memory and the method of opposition

Priming in an indirect test of stem completion should reflect involuntary memory, but can be accompanied by conscious awareness of the past (involuntary conscious memory) or unaccompanied by such awareness (involuntary unconscious memory). We adapted the method of opposition developed by Jacoby, Woloshyn, and Kelley (1989) to obtain a measure of stem-completion priming that should reflect only involuntary unconscious memory. Subjects completed stems with the first word coming to mind, but wrote down a different word if the word that came to mind first had been previously encountered. Facilitatory priming was expected only when involuntary unconscious influences outweighed inhibitory effects of involuntary conscious memory, or of intentional retrieval. We observed a facilitation effect for items processed graphemically at encoding, in conjunction with an inhibition effect for items processed semantically at encoding. In contrast, a standard indirect test showed similar levels of priming following graphemic and semantic encoding, whereas a direct test showed a strong advantage of semantic over graphemic encoding. We argue that the two encoding activities produced approximately equivalent involuntary influences of memory, but that items encoded semantically were associated with involuntary conscious memory to a greater extent than were items encoded graphemically. Comparing indirect and opposition test performance can provide a quantitative index of relative levels of involuntary conscious and involuntary unconscious memory.