Retrieval practice enhances the accessibility but not the quality of memory

Numerous studies have demonstrated that retrieval from long-term memory (LTM) can enhance subsequent memory performance, a phenomenon labeled the retrieval practice effect. However, the almost exclusive reliance on categorical stimuli in this literature leaves open a basic question about the nature of this improvement in memory performance. It has not yet been determined whether retrieval practice improves the probability of successful memory retrieval or the quality of the retrieved representation. To answer this question, we conducted three experiments using a mixture modeling approach (Zhang & Luck, 2008) that provides a measure of both the probability of recall and the quality of the recalled memories. Subjects attempted to memorize the color of 400 unique shapes. After every 10 images were presented, subjects either recalled the last 10 colors (the retrieval practice condition) by clicking on a color wheel with each shape as a retrieval cue or they participated in a control condition that involved no further presentations (Experiment 1) or restudy of the 10 shape/color associations (Experiments 2 and 3). Performance in a subsequent delayed recall test revealed a robust retrieval practice effect. Subjects recalled a significantly higher proportion of items that they had previously retrieved relative to items that were untested or that they had restudied. Interestingly, retrieval practice did not elicit any improvement in the precision of the retrieved memories. The same empirical pattern also was observed following delays of greater than 24 hours. Thus, retrieval practice increases the probability of successful memory retrieval but does not improve memory quality.     

Hypothesis generation,probability judgment,and individual differences in working memory capacity

This research examined the role of working memory (WM) in probability judgment and hypothesis generation using a simulated task that involved estimating the likelihood that particular menu items would be ordered by customers at a dinner. Five main findings were observed. First, judgments of the likelihood of individual items were made relative to alternatives retrieved from long-term memory. Second, the number of alternatives retrieved was positively correlated with a measure of WM-capacity (the operation-span task). Third, participants' probability judgments were subadditive (summing to well over 100%). Fourth, the degree to which participants' judgments were subadditive was affected by the number and strength of the alternatives retrieved from long-term memory. Fifth, the degree to which participants were subadditive was negatively correlated with WM-capacity. The results suggest that individual differences in WM-capacity are fundamental to hypothesis generation and probability judgment.     

The phonological loop in task alternation and task repetition

It has recently been proposed that task repetition is easier than task alternation because the appropriate task settings are already present in working memory, whereas during task alternation task settings must be retrieved from long-term memory (Mayr & Kliegl, 2000). The present study tested whether the phonological loop is involved in keeping the relevant task settings active in working memory. It may then be expected that concurrent articulatory suppression would diminish the facilitation associated with task repetition because the phonological loop could no longer maintain the appropriate task settings active in working memory. Both during task repetition and task alternation the relevant task settings should then be retrieved from long-term memory. Three dual-task experiments were conducted. The results of Experiment 1 were in support of our prediction. Experiment 2 replicated the findings of Experiment 1 and showed that the task settings probably represent the adequate response mappings. Experiment 3 ruled out the involvement of the visuo-spatial sketchpad and more general coordination demands during dual tasking.     

The phonological loop in task alternation and task repetition

It has recently been proposed that task repetition is easier than task alternation because the appropriate task settings are already present in working memory, whereas during task alternation task settings must be retrieved from long-term memory (Mayr & Kliegl, 2000). The present study tested whether the phonological loop is involved in keeping the relevant task settings active in working memory. It may then be expected that concurrent articulatory suppression would diminish the facilitation associated with task repetition because the phonological loop could no longer maintain the appropriate task settings active in working memory. Both during task repetition and task alternation the relevant task settings should then be retrieved from long-term memory. Three dual-task experiments were conducted. The results of Experiment 1 were in support of our prediction. Experiment 2 replicated the findings of Experiment 1 and showed that the task settings probably represent the adequate response mappings. Experiment 3 ruled out the involvement of the visuo-spatial sketchpad and more general coordination demands during dual tasking.     

Boundaries of the relation between conscious recollection and source memory for perceptual details

The relation between conscious recollection and source memory for perceptual details was investigated in three experiments that combined the remember-know paradigm with a multidimensional source monitoring test. Experiment 1 replicated that source memory for perceptual details is better in the case of "remember" than "know" judgments. Experiment 2 showed that the relation between "remember" judgments and source memory for perceptual details is diminished by a semantic orienting task during encoding. Experiment 3 demonstrated that "remember" judgments are related to enhanced source memory for specific and unique kinds of perceptual source information, whereas memory for incomplete and global perceptual source information does not differentiate between "remember" and "know" judgments. The results show that the attentional focus during encoding and the specificity of retrieved source information form boundary conditions for the use of source memory for perceptual details as a basis of "remember" judgments.     

Working memory capacity and retrieval from long-term memory: the role of controlled search

In two experiments, the role of working memory capacity (WMC) in the controlled search of long-term memory was examined. Participants performed a prolonged category fluency task that required them to retrieve as many animals as possible in 5 min. The results suggested that WMC differences arose in the numbers of animals retrieved, the numbers of clusters retrieved, and the rates of the retrieval (Exp. 1). However, no differences were found in terms of how participants initiated retrieval or in the nature of the clusters generated. Furthermore, an examination of differences in retrieval strategies suggested that high-WMC individuals were more strategic than low-WMC individuals and that these differences in retrieval strategies accounted for the overall differences in the numbers of animals retrieved. Additionally, presenting participants with retrieval cues eliminated WMC differences in the numbers of animals retrieved (Exp. 2). These results suggest that low-WMC individuals are less able than high-WMC individuals to select and utilize appropriate retrieval strategies to self-generate cues to access information in long-term memory. Collectively, the results are consistent with research suggesting that WMC is important for controlled search from long-term memory.     

Post-retrieval effects of icv infusions of hemicholinium in mice are dependent on the age of the original memory

CF-1 male mice were trained in an inhibitory avoidance task using a high footshock (1,2 mA, 50 Hz, 1 sec) in order to reduce the influence of extinction on retention performance. At 2, 7, 14, or 30 d after training, the first retention test was performed and hemicholinium (HC-3, 1.0 microg/mice), a specific inhibitor of high-affinity choline uptake in brain cholinergic neurons, was given intracerebroventricularly immediately after. Twenty four hours after treatment, mice were tested in an inhibitory avoidance task during five consecutive days, each 24 h apart. Retention performance was impaired by HC-3 when the first re-exposure took place at 2, 7, or 14 d, but the effect was no longer seen when re-exposure occurred 30 d after training. We did not find spontaneous recovery 21 d after training, when memory was retrieved 2 d after training and HC-3 was given immediately after. Although we cannot definitively discard a retrieval deficit, this lack of spontaneous recovery is in accordance with the storage-deficit interpretation. These results confirm and extend previous ones, suggesting that central cholinergic mechanisms are involved in the hypothetical reconsolidation memory processes of an inhibitory avoidance task in mice and also suggest that this participation depends on the "age" of the original memory trace. This implies that the vulnerability of a reactivated memory to a specific treatment, as the one used in this study, inversely correlates with the age of the original memory, and it is likely to determine memory reconsolidation processes.     

PET studies of encoding and retrieval: The HERA model

We review positron emission tomography (PET) studies whose results converge on the hemispheric encoding/retrieval asymmetry (HERA) model of the involvement of prefrontal cortical regions in the processes of human memory. The model holds that the left prefrontal cortex is differentially more involved in retrieval of information from semantic memory, and in simultaneously encoding novel aspects of the retrieved information into episodic memory, than is the right prefrontal cortex. The right prefrontal cortex, on the other hand, is differentially more involved in episodic memory retrieval than is the left prefrontal cortex. This general pattern holds for different kinds of information (e.g., verbal materials, pictures, faces) and a variety of conditions of encoding and retrieval.     

When the "I" looks at the "Me": autobiographical memory, visual perspective, and the self

This article presents a theoretical model of the self processes involved in autobiographical memories and proposes competing hypotheses for the role of visual perspective in autobiographical memory retrieval. Autobiographical memories can be retrieved from either the 1st person perspective, in which individuals see the event through their own eyes, or from the 3rd person perspective, in which individuals see themselves and the event from the perspective of an external observer. A growing body of research suggests that the visual perspective from which a memory is retrieved has important implications for a person’s thoughts, feelings, and goals, and is integrally related to a host of self-evaluative processes. We review the relevant research literature, present our theoretical model, and outline directions for future research.     

Contributions of the medial temporal lobe to declarative memory retrieval: manipulating the amount of contextual retrieval

We investigated how the hippocampus and its adjacent mediotemporal structures contribute to contextual and noncontextual declarative memory retrieval by manipulating the amount of contextual information across two levels of the same contextual dimension in a source memory task. A first analysis identified medial temporal lobe (MTL) substructures mediating either contextual or noncontextual retrieval. A linearly weighted analysis elucidated which MTL substructures show a gradually increasing neural activity, depending on the amount of contextual information retrieved. A hippocampal engagement was found during both levels of source memory but not during item memory retrieval. The anterior MTL including the perirhinal cortex was only engaged during item memory retrieval by an activity decrease. Only the posterior parahippocampal cortex showed an activation increasing with the amount of contextual information retrieved. If one assumes a roughly linear relationship between the blood-oxygenation level-dependent (BOLD) signal and the associated cognitive process, our results suggest that the posterior parahippocampal cortex is involved in contextual retrieval on the basis of memory strength while the hippocampus processes representations of item-context binding. The anterior MTL including perirhinal cortex seems to be particularly engaged in familiarity-based item recognition. If one assumes departure from linearity, however, our results can also be explained by one-dimensional modulation of memory strength.     

Distinct prefrontal molecular mechanisms for information storage lasting seconds versus minutes

The prefrontal cortex (PFC) is known to actively hold information "online" for a period of seconds in working memory for guiding goal-directed behavior. It has been proposed that relevant information is stored in other brain regions, which is retrieved and held in working memory for subsequent assimilation by the PFC in order to guide behavior. It is uncertain whether PFC stores information outside the temporal limits of working memory. Here, we demonstrate that although enhanced cAMP-dependent protein kinase A (PKA) activity in the PFC is detrimental to working memory, it is required for performance in tasks involving conflicting representations when memory storage is needed for minutes. This study indicates that distinct molecular mechanisms within the PFC underlie information storage for seconds (working memory) and for minutes (short-term memory). In addition, our results demonstrate that short-term memory storage within the prefrontal cortex is required for guiding behavior in tasks with conflicts and provides a plausible mechanism by which the prefrontal cortex executes cognitive control.     

Attention on our mind: The role of spatial attention in visual working memory

The current study shows that spatial visual attention is used to retrieve information from visual working memory. Participants had to keep four colored circles in visual working memory. While keeping this information in memory we asked whether one of the colors was present in the array. While retrieving this information, on some trials a probe dot was presented. When this probe dot was presented at the location of the color that had to be retrieved, participants responded faster than when it was presented at another location. Our findings further elaborate the role of visual attention in working memory: not only is attention the mechanism by which information is stored into working memory, it is also the mechanism by which information is retrieved from visual working memory.     

Protein synthesis underlies post-retrieval memory consolidation to a restricted degree only when updated information is obtained

Consolidation theory proposes that through the synthesis of new proteins recently acquired memories are strengthened over time into a stable long-term memory trace. However, evidence has accumulated suggesting that retrieved memory is susceptible to disruption, seeming to consolidate again (reconsolidate) to be retained in long-term storage. Here we show that intracortical blockade of protein synthesis in the gustatory cortex after retrieval of taste-recognition memory disrupts previously consolidated memory to a restricted degree only if the experience is updated. Our results suggest that retrieved memory can be modified as part of a mechanism for incorporating updated information into previously consolidated memory.     

The cost in remembering of ruminating on negative memories

This study investigated retrieval mechanisms that may be involved in memory for distressing stimuli. Forty-one nonclinical participants watched a video clip depicting the immediate aftermath of a serious car accident. Following this, half of the participants were instructed to focus attention on the victims of the accident and to consider the negative sequelae of their injuries. The remaining participants were not given any instructions. Following the Victim Focus/Control period, all participants completed a cued-recall task assessing their memory of the video clip. Overall, victim-related details were better recalled than nonvictim related details. It is important to note that participants in the Victim Focus condition retrieved fewer peripheral details than participants in the Control condition. These results suggest that people focusing attention on distressing aspects of an event can experience a cost in remembering other aspects of the event. These findings may be interpreted in terms of enhanced recollection of central events or retrieval-induced forgetting mechanisms to explain patterns of diminished memory for aspects of distressing events.     

Interactive visual and postvisual processes and their roles in form-specific memory.

Effects of depth of encoding on form-specific memory were examined. After viewing words (e.g., "bear") presented centrally during initial encoding, participants completed word stems (e.g., "BEA") presented laterally and pattern masked during subsequent test. When the encoding task was perceptual, letter-case specific memory was not observed, unlike in previous experiments without pattern masking. However, when the encoding task required both perceptual and conceptual processing, letter-case specific memory was observed in direct right-hemisphere, but not in direct left-hemisphere, test presentations, like in previous studies without pattern masking. Results were not influenced by whether stems were completed to form the first words that came to mind or words explicitly retrieved from encoding. Depth of encoding may influence form-specific memory through interactive processing of visual and postvisual information.     

Interactions between working memory, attention and eye movements

This paper reviews the recent findings on working memory, attention and eye movements. We discuss the research that shows that many phenomena related to visual attention taking place when selecting relevant information from the environment are similar to processes needed to keep information active in working memory. We discuss new data that show that when retrieving information from working memory, people may allocate visual spatial attention to the empty location in space that used to contain the information that has to be retrieved. Moreover, we show that maintaining a location in working memory not only may involve attention rehearsal, but might also recruit the oculomotor system. Recent findings seem to suggest that remembering a location may involve attention-based rehearsal in higher brain areas, while at the same time there is inhibition of specific motor programs at lower brain areas. We discuss the possibility that working memory functions do not reside at a special area in the brain, but emerge from the selective recruitment of brain areas that are typically involved in spatial attention and motor control.     

Retrieval processes in restructuring: Answer to Keane

In a comment on the attempt by Ohlsson (1984) to interpret the Gestalt theory of restructuring and insight in information processing terms, Keane argues that memory retrieval is central to restructuring and that Ohlsson ignores higher-order memory organizations. Careful comparison between Ohlsson's and Keane's hypotheses about what kind of retrieval occurs in restructuring reveals that they take different stands on three well-known issues in the study of knowledge representation: semantic vs. episodic memory, declarative vs. procedural knowledge, and "small" vs. "large" memory units. Since humans obviously have several types of memory units, both types of retrieval processes may be involved in restructuring.     

When Knowing Becomes Remembering: Individual Differences in Susceptibility to Suggestion

In two experiments, the authors explored factors that might influence a person's tendency to make source-monitoring errors about autobiographical memories. In the first experiment, undergraduates retrieved a memory from childhood (a) that was known about but not remembered, (b) that was remembered, or (c) for which they were unsure of their memory's source. After writing down the memory, experimental groups listened to a guided visualization tape and answered questions about the event—interventions designed to help them focus on details of their memory. Controls also retrieved and wrote down a memory; however, instead of visualizing the memory, they were instructed to conduct a visual search task. Results indicated that guided visualization led participants to rate known memories closer to remembered events. A second experiment examined individual difference variables that might be related to this know-to-remember shift. Results indicated that extraversion, external locus of control, a memory that conveyed fear, and overall affective content predicted this rating. The applicability of these findings to the psychotherapy process is discussed.     

When knowing becomes remembering: individual differences in susceptibility to suggestion

In two experiments, the authors explored factors that might influence a person's tendency to make source-monitoring errors about autobiographical memories. In the first experiment, undergraduates retrieved a memory from childhood (a) that was known about but not remembered, (b) that was remembered, or (c) for which they were unsure of their memory's source. After writing down the memory, experimental groups listened to a guided visualization tape and answered questions about the event--interventions designed to help them focus on details of their memory. Controls also retrieved and wrote down a memory; however, instead of visualizing the memory, they were instructed to conduct a visual search task. Results indicated that guided visualization led participants to rate known memories closer to remembered events. A second experiment examined individual difference variables that might be related to this know-to-remember shift. Results indicated that extraversion, external locus of control, a memory that conveyed fear, and overall affective content predicted this rating. The applicability of these findings to the psychotherapy process is discussed.     

Organization in autobiographical memory

Three experiments investigated timed autobiographical memory retrieval to cue words and phrases. In the first experiment, subjects retrieved memories to cues that named semantic category members and were primed with the superordinate category name or with a neutral word. No prime effects were observed. In the second experiment, subjects retrieved memories to primed and unprimed semantic category cues and to personal primes and personal history cues. Personal primes named lifetime periods (e.g., “school days”) and personal history cues named general events occurring in those lifetime periods for each subject (e.g., “holiday in Italy”). Only personal primes were found to significantly facilitate memory retrieval. A third experiment replicated this finding and also failed to find any prime effects to primes and cues naming activities not directly related to an individual’s personal history. In this experiment, characteristics of recalled events (e.g,, personal importance, frequency of rehearsal, pleasantness, and specificity of the memory) were found to be strongly associated with memories retrieved to personal cues and only mildly associated with memories retrieved to other types of cues. These findings suggest that one way in which autobiographical memories may be organized is in terms of a hierarchically structured abstracted personal history.