Involuntary conscious memory and the method of opposition

When trying to recall our past, all roads lead to Rome: More evidence for the multi-process retrieval theory of autobiographical memory

In this study, we tested elements of the multi-process retrieval account of autobiographical memory, retrieval multiplicity, and retrieval selectivity. The retrieval multiplicity states that multiple different retrieval strategies are used to recall autobiographical memories, while the retrieval selectivity states that such retrieval strategies will vary in accord with the cuing environment. We tested these hypotheses across two experiments with the retrieve-aloud procedure. In the retrieve-aloud procedure, participants were required to verbalize their thoughts while attempting to retrieve personal memories in response to phrase cues (e.g., listening to music). Experiments 1 and 2 found support for the retrieval multiplicity by showing that participants used a variety of different retrieval processes (eight different processes in total), while Experiment 1 found support for the retrieval selectivity by showing that retrieval strategies varied across different cue types. The implications of the findings are discussed with respect to autobiographical memory, as well as semantic memory.

The Directed Forgetting Effect in Word-fragment Completion: An Application of the Process Dissociation Procedure

In three experiments, subjects were asked to remember and forget study words. In line with previous studies, a directed forgetting effect was observed in a word-fragment completion task: Instructions to remember increased the completion of target fragments compared with instructions to forget (Experiment 1). Using the process dissociation procedure (Jacoby, 1991), it appeared that instructions to remember increased the estimates of intentional influences of memory but did not affect the estimates of automatic uses of memory (Experiments 1, 2 and 3). This suggests that directed forgetting effects in word-fragment completion reflect the surreptitious influence of explicit memory in a nominally implicit memory task. However, a meta-analysis indicated that directed forgetting instructions affected automatic and intentional influences of memory in opposite directions. This finding casts doubt on the assumption of independence between automatic and intentional uses of memory. The implications for use of the process dissociation procedure are discussed.

Effects of Saccade Induced Retrieval Enhancement on conceptual and perceptual tests of explicit & implicit memory

The effects of saccadic horizontal (bilateral) eye movements upon tests of both conceptual and perceptual forms of explicit and implicit memory were investigated. Participants studied a list of words and were then assigned to one of four test conditions: conceptual explicit, conceptual implicit, perceptual explicit, or perceptual implicit. Conceptual tests comprised category labels with either explicit instructions to recall corresponding examples from the study phase (category-cued recall), or implicit instructions to generate any corresponding examples that spontaneously came to mind (category-exemplar generation). Perceptual tests comprised of word-fragments with either explicit instructions to complete these with study items (word-fragment-cued recall), or implicit instructions to complete each fragment with the first word that simply 'popped to mind' (word-fragment completion). Just prior to retrieval, participants were required to engage in 30 s of bilateral vs. no eye movements. Results revealed that saccadic horizontal eye movements enhanced performance in only the conceptual explicit condition, indicating that Saccade-Induced Retrieval Enhancement is a joint function of conceptual and explicit retrieval mechanisms. Findings are discussed from both a cognitive and neuropsychological perspective, in terms of their potential functional and neural underpinnings.

Implicit Memory in Amnesic Patients: Impairment of Voice-Specific Priming

Amnesic patients generally exhibit spared priming effects on implicit memory tasks despite poor explicit memory In a previous study, we demonstrated normal auditory priming in amnesic patients on an identification-in-noise test in which the magnitude of priming is independent of whether the speaker's voice is the same or different at study and test In the present experiment, we examined auditory priming on a filter identification test in which the magnitude of priming in control subjects is higher when the speaker's voice is the same at study and test than when it is different Amnesic patients, by contrast, failed to exhibit more priming in a same-voice condition than in a different-voice condition Voice-specific priming may depend on a memory system that is impaired in amnesia

Implicit memory influences on metamemory during verbal learning after traumatic brain injury

PURPOSE

Prior research has shown that individuals with traumatic brain injury (TBI) may be overconfident in their judgments of learning (JOLs; online measures of self-monitoring of learning and memory). JOLs had been presumed to be driven by explicit processes, but recent research has also revealed implicit memory involvement. Given that implicit learning mechanisms are often intact in those with TBI, the purpose of this study was to investigate whether priming and antipriming of immediate and delayed JOLs in individuals with TBI might affect their overconfidence.

METHOD

A standard 3-field masked priming paradigm was combined with a paired-associate learning task with JOLs and administered to individuals with TBI and matched controls (18 per group). In each trial, a subliminal masked stimulus was immediately followed by supraliminal presentation of a word pair for study; participants also made immediate and delayed JOLs, with cued-recall testing 10 min after study and judgment.

RESULTS

Antipriming significantly lowered JOLs and overconfidence for both groups, whereas delaying JOLs significantly improved recall for both groups.

CONCLUSIONS

The results suggest that JOLs may be influenced by subliminal implicit memory. Clinical implications include the possible use of antipriming to reduce overconfidence after brain injury and delaying JOLs to improve recall.

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.

Imagery in the aftermath of viewing a traumatic film: using cognitive tasks to modulate the development of involuntary memory

BACKGROUND AND OBJECTIVES

Involuntary autobiographical memories that spring unbidden into conscious awareness form part of everyday experience. In psychopathology, involuntary memories can be associated with significant distress. However, the cognitive mechanisms associated with the development of involuntary memories require further investigation and understanding. Since involuntary autobiographical memories are image-based, we tested predictions that visuospatial (but not other) established cognitive tasks could disrupt their consolidation when completed post-encoding.

METHODS

In Experiment 1, participants watched a stressful film then immediately completed a visuospatial task (complex pattern tapping), a control-task (verbal task) or no-task. Involuntary memories of the film were recorded for 1-week. In Experiment 2, the cognitive tasks were administered 30-min post-film.

RESULTS

Compared to both control and no-task conditions, completing a visuospatial task post-film reduced the frequency of later involuntary memories (Expts 1 and 2) but did not affect voluntary memory performance on a recognition task (Expt 2).

LIMITATIONS

Voluntary memory was assessed using a verbal recognition task and a broader range of memory tasks could be used. The relative difficulty of the cognitive tasks used was not directly established.

CONCLUSIONS

An established visuospatial task after encoding of a stressful experience selectively interferes with sensory-perceptual information processing and may therefore prevent the development of involuntary autobiographical memories.

Distinct frontoparietal networks set the stage for later perceptual identification priming and episodic recognition memory

Recent imaging evidence suggests that a network of brain regions including the medial temporal lobe, ventrolateral prefrontal cortex, and dorsal posterior parietal cortex supports the successful encoding of long-term memories. Other areas, like the ventral posterior parietal and dorsolateral prefrontal cortices, have been associated with encoding failure rather than success. In line with the transfer-appropriate processing view, we hypothesized that distinct neural networks predict successful encoding depending on whether the later memory test draws primarily on perceptual or conceptual memory representations. Following an encoding phase, memory was assessed in a combined incidental perceptual identification and intentional recognition memory test. We found that during encoding, activation in ventral posterior parietal and dorsolateral prefrontal cortex predicted successful perceptual identification priming, whereas activation in ventrolateral prefrontal and dorsal posterior parietal cortex predicted successful recognition memory. Extending recent theories of attention to memory, the results suggest that ventral parietal regions support stimulus-driven attention to perceptual item features, forming memories accessed by later perceptual memory tests, whereas dorsal parietal regions support attention to meaningful item features, forming memories accessed by later conceptual memory tests.

Priming effects from young-old to very old age on a word-stem completion task: minimizing explicit contamination

We investigated the size of repetition priming effects from young-old to very old age using a newly developed Word-Stem Completion (WSC) task. Retrospectively, we examined the role of explicit, intentional retrieval strategies in priming. We constructed our task by taking factors into account that were known to complicate the measurement of significant and valid priming effects. Within our sample of 170 cognitively healthy elderly persons of 55-94 years old, we found no effects on priming of age, gender, education, intelligence, cognitive status, memory complaints, or depressive symptoms. Participants that subsequent to task administration reported awareness of the study-test relationship obtained higher priming scores. However, analysis of stem-completion times showed that explicit contamination during the task was unlikely. The results suggest that WSC priming is age-invariant up to very old age. This task with increased validity might contribute to the differentiation with Alzheimer's disease by improving specificity of assessment.

Number of solutions effects in stem decision: Support for the distinction between identification and production processes in priming

Three experiments explored the distinction between identification and production processes (e.g., Gabrieli et al., 1999). A stem decision test was introduced, in which participants were asked to state whether there were any English words that began with the presented three-letter stems. In Experiment 1, stem decision priming was robust for single-solution stems, but much reduced for many-solution stems. In Experiment 2, the solutions effect in stem decision was replicated in a within-subjects design, as was the contrast between the presence of priming in a many-solution stem completion test and the absence of priming in a many-solution stem decision test. In Experiment 3, for each critical many-solution stem in the stem decision test, participants studied three words that began with those three letters. Again, priming was not observed. These results were consistent with the notions that (a) many-solution stem completion relies on production processes, (b) the stem decision test eliminates production processes, and (c) single-solution priming relies on identification processes, regardless of whether the test is stem completion or stem decision.

Aging and implicit memory: examining the contribution of test awareness

The study examined whether test awareness contributes to age effects in priming. Younger and older adults were given two priming tests (word-stem completion and category production). Awareness was assessed using both a standard post-test questionnaire and an on-line measure. Results from the on-line awareness condition showed that, relative to older adults, younger adults showed higher levels of priming and awareness, and a stronger relationship between the two, suggesting that awareness could account for age differences in priming. In contrast, in the post-test questionnaire condition, there was no age effect in word-stem completion or category production priming, despite the fact that awareness was greater in younger than older adults in the word-stem completion test and that category production priming was dependent on awareness in both age groups. These results suggest that awareness may mediate age effects in priming, but only under conditions of relatively high levels of awareness.

Event-related potential evidence that automatic recollection can be voluntarily avoided

Voluntary control processes can be recruited to facilitate recollection in situations where a retrieval cue fails to automatically bring to mind a desired episodic memory. We investigated whether voluntary control processes can also stop recollection of unwanted memories that would otherwise have been automatically recollected. Participants were trained on cue-associate word-pairs, then repeatedly presented with the cue and asked to either recollect or avoid recollecting the associate, while having the event-related potential (ERP) correlate of conscious recollection measured. Halfway through the phase, some cues switched instructions so that participants had to start avoiding recall of associates they had previously repeatedly recalled, and vice versa. ERPs during recollection avoidance showed a significantly reduced positivity in the correlate of conscious recollection, and switching instructions reversed the ERP effect even for items that had been previously repeatedly recalled, suggesting that voluntary control processes can override highly practiced, automatic recollection. Avoiding recollection of particularly prepotent memories was associated with an additional, earlier ERP negativity that was separable from the later voluntary modulation of conscious recollection. The findings have implications for theories of memory retrieval by highlighting the involvement of voluntary attentional processes in controlling conscious recollection.

The frequency of voluntary and involuntary autobiographical memories across the life span

In the present study, ratings of the memory of an important event from the previous week on the frequency of voluntary and involuntary retrieval, belief in its accuracy, visual imagery, auditory imagery, setting, emotional intensity, valence, narrative coherence, and centrality to the life story were obtained from 988 adults whose ages ranged from 15 to over 90. Another 992 adults provided the same ratings for a memory from their confirmation day, when they were at about age 14. The frequencies of involuntary and voluntary retrieval were similar. Both frequencies were predicted by emotional intensity and centrality to the life story. The results from the present study-which is the first to measure the frequency of voluntary and involuntary retrieval for the same events-are counter to both cognitive and clinical theories, which consistently claim that involuntary memories are infrequent as compared with voluntary memories. Age and gender differences are noted.

Are awareness questionnaires valid? Investigating the use of posttest questionnaires for assessing awareness in implicit memory tests

Two experiments--one employing a perceptual implicit memory test and the other a conceptual implicit memory test--investigated the validity of posttest questionnaires for determining the incidence of awareness in implicit memory tests. In both experiments, a condition in which none of the studied words could be used as test responses (i.e., the none-studied condition) was compared with a standard implicit test condition. Results showed that reports of awareness on the posttest questionnaire were much less frequent in the none-studied condition than in the standard condition. This was especially true after deep processing at study. In both experiments, 83% of the participants in the none-studied condition stated they were unaware even though there were strong demands for claiming awareness. Although there was a small bias in the questionnaire (i.e., 17% of the participants in the none-studied condition stated they were aware), overall, there was strong support for the validity of awareness questionnaires.

Episodic remembering creates access to involuntary conscious memory: demonstrating involuntary recall on a voluntary recall task

The idea that involuntary memory retrieval might occur during voluntary memory retrieval can be traced back to Ebbinghaus (1885/1964). However, methodological challenges have stood in the way of testing this idea. Recent diary studies of naturally occurring involuntary memories have provided insights into how this idea could be tested (Berntsen, 1998; Mace, 2005b, 2006). These studies have shown that the contents of an involuntary memory sometimes trigger additional involuntary memories, a process called chaining. It was hypothesised that chaining should also occur on autobiographical memory tasks, and this was tested in the present study by asking participants in an autobiographical memory task to report the presence of involuntary memories while they were performing the task. The results showed that involuntary memories did occur when participants were recalling the past. The results also showed involuntary memories dissociating from voluntary memories on two independent measures, thereby enhancing the credibility of the results.

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.

Effects of Age and Divided Attention on Memory Components Derived for the Category Exemplar Generation Task

Age differences in memory performances on a conceptually driven task, the category exemplar generation (CEG) test, were investigated. Thirty-six younger adults and 36 healthy older adults studied word lists in full and divided attention conditions. Recall was tested with category names. The process-dissociation procedure was used to derive estimates of controlled and automatic memory. Old-old adults (70-84 years) exhibited poorer conscious recollection than both younger (18-24) and young-old adults (59-69). In contrast, no age differences were found in estimates of automatic memory. For the younger and older adults, the divided encoding manipulation reduced both the consciously controlled and automatic estimates of memory. The results suggest that the few prior findings of age deficits in priming on the CEG may have been an artifact of contamination from conscious retrieval processes. They also indicate that the opportunity for greater semantic processing enhances the conceptual priming of both younger and older adults.

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.

Priming involuntary autobiographical memories

Involuntary autobiographical memories occur frequently in daily life and are usually triggered by cues in one's environment. This study investigated the possibility that priming plays a role in the production of involuntary memories. In Study 1, participants recorded their involuntary memories in a diary for 14 days and then completed a questionnaire assessing their cognitive activity during the recording period. Participants indicating frequent thought about significant others on the questionnaire showed significantly more involuntary memories related to such individuals than a control group. In Studies 2 and 3, participants recorded their involuntary memories in diaries for 14 days and were primed with recall sessions in the laboratory during that period (recalling episodes from high school, Study 1, the past year, or ages 13-16, Studies 2 & 3). The results of both studies showed significant priming effects in the involuntary memories of participants for all of the periods primed. The possibility that priming plays a significant role in the daily production of involuntary memories is discussed.

Neuroanatomical dissociation of encoding processes related to priming and explicit memory

Priming is a facilitation of cognitive processing with stimulus repetition that can occur without explicit memory. Whereas the functional neuroanatomy of perceptual priming at retrieval is established, encoding processes that initiate priming and explicit memory have not yet been anatomically separated, and we investigated them using event-related functional magnetic resonance imaging. Activations predicting later explicit memory occurred in the bilateral medial temporal lobe (MTL) and left prefrontal cortex (PFC). Activity predicting later priming did not occur in these areas, but rather in the bilateral extrastriate cortex, left fusiform gyrus, and bilateral inferior PFC, areas linked with stimulus identification. Surprisingly, these regions showed response reductions. Our results demonstrate that priming and explicit memory have distinct functional neuroanatomies at encoding, with MTL activations being specific for explicit memory, and suggest that priming is initiated by sharpness of neural responding in stimulus identification areas, consistent with recent electrophysiological evidence regarding priming-related neural oscillations at encoding. We tentatively suggest that this sharpened responding at encoding may set the stage for increased neural processing efficiency at retrieval, with these different neural mechanisms both leading to observed priming-related hemodynamic decreases, and argue that neural measurements at encoding, and not just at retrieval, will be critical in resolving the debate about the neural mechanisms of learning that underlie priming.

Does priming with awareness reflect explicit contamination? An approach with a response-time measure in word-stem completion

The present experiment investigates the involvement of awareness in functional dissociations between explicit and implicit tests. In the explicit condition, participants attempted to recall lexically or semantically studied words using word stems. In the implicit condition, they were instructed to complete each stem with the first word which came to mind. Subjective awareness was subsequently measured on an item-by-item basis. As voluntary retrieval strategies are known to be time consuming, the time taken to complete each stem was recorded. In the explicit task, semantically studied words were associated with higher levels of recall and faster response times than lexically studied words. By contrast, in the implicit task, these effects failed to reach significance, although deep encoding made the contents of memory more accessible to awareness. As expected, performance was slower in the explicit than in the implicit task, but in the latter condition, times to produce old words with and without awareness were comparable, and both of these responses were produced more quickly than control words. This finding suggests that although participants may become aware in implicit paradigms, they do not adopt voluntary retrieval strategies.

Measuring automatic retrieval: a comparison of implicit memory, process dissociation, and speeded response procedures

Using the stem completion task, we compared estimates of automatic retrieval from an implicit memory task, the process dissociation procedure, and the speeded response procedure. Two standard manipulations were employed. In Experiment 1, a depth of processing effect was found on automatic retrieval using the speeded response procedure although this effect was substantially reduced in Experiment 2 when lexical processing was required of all words. In Experiment 3, the speeded response procedure showed an advantage of full versus divided attention at study on automatic retrieval. An implicit condition showed parallel effects in each study, suggesting that implicit stem completion may normally provide a good estimate of automatic retrieval. Also, we replicated earlier findings from the process dissociation procedure, but estimates of automatic retrieval from this procedure were consistently lower than those from the speeded response procedure, except when conscious retrieval was relatively low. We discuss several factors that may contribute to the conflicting outcomes, including the evidence for theoretical assumptions and criterial task differences between implicit and explicit tests.

Abstractionist versus exemplar-based theories of visual word priming: a subsystems resolution

Three experiments addressed abstractionist versus exemplar-based theories of the visual representations underlying word priming. Participants first read centrally presented whole words (each displayed in all lowercase or in all uppercase letters), and then they completed laterally presented word stems (each displayed in all lowercase or in all uppercase letters). Word stem completion priming was letter-case specific (greater for same-case primed items than for different-case primed items) when stems were presented directly to the right cerebral hemisphere but not when stems were presented directly to the left cerebral hemisphere. This interaction was not influenced by the typicality of the test stems, but it was observed only for stems composed of letters with visually dissimilar lowercase and uppercase structures (e.g., bea/BEA) and not for stems composed of letters with visually similar lowercase and uppercase structures (e.g., sco/SCO). In contrast, cued recall was letter-case specific when similar-case or dissimilar-case stems were presented directly to the right hemisphere. Results do not support strongly abstractionist or exemplar-based theories. Instead, they suggest a resolution to these differing perspectives: Relatively independent neural subsystems operate in parallel to underlie abstract-category and specific-exemplar priming of word forms.

Explicit Contamination Contributes to Aging Effects in Episodic Priming: Behavioral and ERP Evidence

We examined the impact of explicit contamination on age-related changes in episodic priming. We recorded event-related brain potentials (ERPs) from older and younger adults to primed and unprimed nouns tested in a recognition memory task. Results revealed that the magnitude of priming was greater in the younger adults. ERPs revealed a priming effect in the younger adults that was absent in older adults. Findings suggest that explicit contamination may account for the reported aging effect: Item memory was correlated with episodic priming and ERP priming in younger adults, but not older adults; item memory was associated with episodic priming after aging effects were controlled for; and the topographies of the young's priming and item memory effects were indistinguishable. Given the apparent vulnerability to contamination by explicit memory, we suggest caution when researchers use an episodic priming paradigm to assess aging effects in implicit memory.

The episodic nature of involuntary autobiographical memories

Involuntary autobiographical memories are conscious and unintended recollections of personal experiences. In Study 1, involuntary memories were compared with voluntary word-cued memories, both retrieved in naturalistic settings via a self-paced procedure. The involuntary memories more frequently referred to specific episodes, came with more physical reaction, had more impact on mood, and dealt with more unusual and less positive events. Study 2 demonstrated that these differences were not due to differences between verbal and nonverbal cues, by using Francis Galton's "memory walk" as a nonverbal method to cue voluntary memories. In both studies, systematic differences were found between specific and nonspecific memories. The findings show that the way autobiographical memories are sampled greatly affects the findings and that involuntary retrieval more often provides access to memories of specific episodes and associated emotional states.

Stem-completion tasks (indirect, direct inclusion and exclusion) are differently affected by equipotent doses of lorazepam and flunitrazepam

This study was designed to explore the effects on performance in stem-completion tasks of two benzodiazepines (BZ) in equipotent doses: lorazepam, a drug that atypically disrupts perceptual priming, and flunitrazepam, a compound with standard BZ effects. The study followed a placebo-controlled, double-blind, parallel-group design. Thirty-six young and healthy subjects carried out three completion tasks at theoretical peak-plasma concentrations of drugs: (a) indirect tasks, in which the subjects were instructed to complete stems with the first word that came to mind; (b) direct inclusion tasks/cued recall, in which the participants had to try to use words seen at study as completions; and (c) direct exclusion tasks, in which words seen at study were to be avoided. The PDP was applied to the results in the inclusion and exclusion tasks, to obtain indices of explicit/controlled (C) and implicit/automatic (A) memory. The C index was lowered by both BZs and A was equivalent in all treatments, confirming the general amnestic action of BZs. However, lorazepam led to decreases in completions in the indirect and inclusion tasks, while flunitrazepam impaired performance in the exclusion task. The qualitative differences between the drugs in their effects on performance suggest that these BZs may lead to differences in response bias.

Process dissociation using a guided procedure

A method for achieving process dissociation is described that places less emphasis on participants' understanding and remembering interpretations of test cues than does the standard procedure. The proposed method, called the guided procedure, tests memory with a sequence of two prompts, one requesting word-stem recognition, followed by another for word-stem completion. Inclusion and exclusion conditions are produced by requesting completion of recognized stems to form previously presented or new words, respectively. Estimates of automatic and conscious memory produced by the standard and the guided procedures are compared in studies modeled after Toth, Reingold, and Jacoby (1994). Although not significantly different in many aspects, the outcomes differ in ways that may reflect less reliance on a generate-recognize strategy of participants tested with the guided procedure. Additional measures of memory available only with the guided procedure are presented.

Level of processing and the process-dissociation procedure: elusiveness of null effects on estimates of automatic retrieval

We describe two experiments that used the process-dissociation procedure to investigate the effects of level of processing on estimates of controlled and automatic retrieval processes in word-stem completion tasks. Despite our best endeavours, we found the null effect of level of processing on estimates of automatic retrieval reported by Toth, Reingold, and Jacoby (1994) elusive. Estimates of automatic retrieval were not independent of level of processing but inversely related to it. In part, the reason was that, following deeper levels of processing, instructions to exclude recollected words led to floor effects. But the inverse relationship persisted even when floor effects were avoided. Only participants who were not given strict instructions in the exclusion task-and who also qualified as lax responders based on answers in a structured post-test interview-showed no effect of level of processing on estimates of automatic retrieval. This null effect apparently occurred because these participants failed to exclude words that they in fact recollected from the study list. This finding violates the critical assumption that in this task participants exclude recollected words. The results are therefore paradoxical. Successful replication of the null effect occurred only under conditions that preclude the very use of the procedure. This paradox has important implications for views on how consciousness should be conceived in relation to memory.

Process-dissociation procedure: a testable model for considering assumptions about the stochastic relation between consciously controlled and automatic processes

This paper presents an extension of the process-dissociation procedure with wordstem completion, which makes possible the measurement of the stochastic relationship between consciously controlled and automatic processes. By means of an indirect wordstem completion test, the conditional probabilities of conscious remembering with and without automatic processes can be successfully determined. A multinomial model for the evaluation of this extended process-dissociation procedure is presented. This model makes the distinction between voluntary and involuntary conscious memory processes possible and has been applied to two experiments discussed in this paper. The results show that the assumption of stochastic independence is often violated, albeit not as strongly as predicted by the redundancy or exclusivity model variants. Two conscious processes were found, voluntary and involuntary conscious memory processes, each with a different probability of occurrence.

Perceptual priming versus explicit memory: dissociable neural correlates at encoding

We addressed the hypothesis that perceptual priming and explicit memory have distinct neural correlates at encoding. Event-related potentials (ERPs) were recorded while participants studied visually presented words at deep versus shallow levels of processing (LOPs). The ERPs were sorted by whether or not participants later used studied words as completions to three-letter word stems in an intentional memory test, and by whether or not they indicated that these completions were remembered from the study list. Study trials from which words were later used and not remembered (primed trials) and study trials from which words were later used and remembered (remembered trials) were compared to study trials from which words were later not used (forgotten trials), in order to measure the ERP difference associated with later memory (DM effect). Primed trials involved an early (200-450 msec) centroparietal negative-going DM effect. Remembered trials involved a late (900-1200 msec) right frontal, positive-going DM effect regardless of LOP, as well as an earlier (600-800 msec) central, positive-going DM effect during shallow study processing only. All three DM effects differed topographically, and, in terms of their onset or duration, from the extended (600-1200 msec) fronto-central, positive-going shift for deep compared with shallow study processing. The results provide the first clear evidence that perceptual priming and explicit memory have distinct neural correlates at encoding, consistent with Tulving and Schacter's (1990) distinction between brain systems concerned with perceptual representation versus semantic and episodic memory. They also shed additional light on encoding processes associated with later explicit memory, by suggesting that brain processes influenced by LOP set the stage for other, at least partially separable, brain processes that are more directly related to encoding success.

How ”Implicit\ Are Implicit Color Effects in Memory?

Abstract. Processing colored pictures of objects results in a preference to choose the former color for a specific object in a subsequent color choice test ( Wippich & Mecklenbräuker, 1998 ). We tested whether this implicit memory effect is independent of performances in episodic color recollection (recognition). In the study phase of Experiment 1, the color of line drawings was either named or its appropriateness was judged. We found only weak implicit memory effects for categorical color information. In Experiment 2, silhouettes were colored by subjects during the study phase. Performances in both the implicit and the explicit test were good. Selections of ”old\ colors in the implicit test, though, were almost completely confined to items for which the color was also remembered explicitly. In Experiment 3, we applied the opposition technique in order to check whether we could find any implicit effects regarding items for which no explicit color recollection was possible. This was not the case. We therefore draw the conclusion that implicit color preference effects are not independent of explicit recollection, and that they are probably based on the same episodic memory traces that are used in explicit tests.

The role of explicit memory processes in cross-modal priming: an investigation of stem completion priming in amnesia

To clarify the role of explicit memory processes in cross-modal priming, two experiments examined the status of cross-modal stem completion priming in amnesia. Experiment 1 used a standard behavioral paradigm in which stems corresponding to studied and unstudied words were intermixed. Amnesic patients showed intact within- and cross-modal priming, but, in contrast to controls, they recognized very few of their completions as having been on the study list. This finding suggests that memorial awareness is not necessary for cross-modal priming to occur. Experiment 2 used a paradigm modeled after functional imaging studies, in which stems corresponding to studied and unstudied words were blocked. Amnesic patients showed intact within-modal priming, but impaired cross-modal priming. This finding is consistent with the notion that a blocked format induces voluntary retrieval strategies in normal participants.

Verschwinden Dissoziationen zwischen implizitem und explizitem Gedächtnis, wenn die Reliabilität der Tests vergleichbar ist? Ein Beispiel

Zusammenfassung. Implizite Gedächtnistests tendieren dazu, weniger reliabel als explizite Gedächtnistests zu sein. Daraus folgt, dass Dissoziationen aufgrund unterschiedlicher Reliabilität der Aufgabe zustande kommen können. In der vorliegenden Studie wird der Effekt der Verarbeitungstiefe auf einen impliziten und einen expliziten Gedächtnistest bei einer Stichprobe von 200 Versuchspersonen untersucht. Als impliziter Test wurde die Benennung fragmentierter Objekte, als expliziter Test eine Rekognitionsaufgabe verwendet. Beide Testarten wiesen eine vergleichbare Reliabilität auf. Es zeigte sich ein Effekt der Verarbeitungstiefe auf beide Tests, aber keine Interaktion zwischen Testart und Verarbeitungstiefe. Dieser Befund bestärkt die Notwendigkeit der Berücksichtigung der Reliabilität für die Interpretation von Dissoziationen zwischen implizitem und explizitem Gedächtnis.

Measuring automatic retrieval

A variety of procedures have been used to assess automatic retrieval effects on memory, including implicit memory tests and the process dissociation approach. Theoretical concerns with each are summarized prior to describing a procedure for evaluating automatic retrieval that is based on retrieval speed. Specifically, in a speeded implicit task, participants were encouraged to complete word stems using strictly automatic retrieval by presenting several practice test trials that did not allow responding based on previously studied items and by encouraging speed of responding. This speeded implicit task was compared with a condition in which conscious retrieval of studied information was not possible and a condition in which conscious retrieval was required, providing converging evidence to support the hypothesis that the speeded implicit procedure can yield pure estimates of automatic retrieval. Furthermore, evidence from a standard implicit memory task yielded comparable data that suggests that participants engaged automatic retrieval processes on this task also.

Implicit memory: intention and awareness revisited

One of the major developments in memory research in the past decade or so has been a growing interest in implicit memory - task performance that is not accompanied by conscious or intentional recollection. In this article, we examine evidence for perceptual and conceptual implicit memory, using the accepted definitions, and suggest that there is in fact a lack of strong evidence for implicit memory in normal subjects. If more convincing evidence cannot be obtained, one solution might be to modify the current terminology. We suggest that the term implicit memory might have outgrown its usefulness as an overall descriptor.

Perceptual specificity in visual object priming: functional magnetic resonance imaging evidence for a laterality difference in fusiform cortex

Seeing an object on one occasion may facilitate or prime processing of the same object if it is later again encountered. Such priming may also be found -- but at a reduced level -- for different but perceptually similar objects that are alternative exemplars or 'tokens' of the initially presented object. We explored the neural correlates of this perceptual specificity using event-related functional magnetic resonance imaging (fMRI) procedures, contrasting neural activity when participants made object classification decisions (size judgments) regarding previously presented objects (repeated same), alternative exemplars of previously presented objects (repeated different), or entirely new objects (novel). Many frontal regions (including bilateral frontal operculum, bilateral posterior inferior frontal/precentral, left anterior inferior frontal, and superior frontal cortices) and multiple late visual and posterior regions (including middle occipital, fusiform, fusiform-parahippocampal, precuneus, and posterior cingulate, all bilaterally), demonstrated reduced neural activity for repeated compared to novel objects. Greater repetition-induced reductions were observed for same than for different exemplars in several of these regions (bilateral posterior inferior frontal, right precuneus, bilateral middle occipital, bilateral fusiform, bilateral parahippocampal and bilateral superior parietal). Additionally, right fusiform (occipitotemporal) cortex showed significantly less priming for different versus same exemplars than did left fusiform. These findings converge with behavioral evidence from divided visual field studies and with neuropsychological evidence underscoring the key role of right occipitotemporal cortex in processing specific visual form information; possible differences in the representational-functional role of left fusiform are discussed.