Segregation accuracy in item‐method directed forgetting across multiple tests

Two experiments examined recall across tests following item‐method directed‐forgetting instructions and the varying of presentation duration of items at study. For both immediate testing (Experiment 1) and delayed testing (Experiment 2), accurate recall of remember instruction items (R‐items) exceeded the accurate recall of forget instruction items (F‐items). However, some F‐items from study were inaccurately recalled as R‐items and R‐items from study as F‐items. Inaccurate recall persisted across tests for both immediate and delayed recall and increased across tests for immediate recall. We view the R‐item advantage in accurate recall as consistent with the account they receive more rehearsal at study than do F‐items. We view inaccurate recall as reflecting the bias to report items retrieved on an immediate test lacking instructional tags as F‐items. On delayed tests, items retrieved lacking instructional tags are first assessed against a criterion point on a memory‐strength continuum and those with strength above the criterion reported as R‐items and those below the criterion as F‐items.     

Incidental retrieval-induced forgetting of location information

Retrieval-induced forgetting (RIF) has been studied with different types of tests and materials. However, RIF has always been tested on the items' central features, and there is no information on whether inhibition also extends to peripheral features of the events in which the items are embedded. In two experiments, we specifically tested the presence of RIF in a task in which recall of peripheral information was required. After a standard retrieval practice task oriented to item identity, participants were cued with colors (Exp. 1) or with the items themselves (Exp. 2) and asked to recall the screen locations where the items had been displayed during the study phase. RIF for locations was observed after retrieval practice, an effect that was not present when participants were asked to read instead of retrieving the items. Our findings provide evidence that peripheral location information associated with an item during study can be also inhibited when the retrieval conditions promote the inhibition of more central, item identity information.     

Encoding location and serial order in auditory working memory: evidence for separable processes

In this study, we investigated the interactions between temporal and spatial information in auditory working memory. In two experiments, participants were presented with sequences of sounds originating from different locations in space and were then asked to recall either their position or their serial order. In Experiment 1, attention during encoding was manipulated by contrasting 'pure' blocks (i.e., location-only or serial-order-only trials) to 'mixed' blocks (i.e., different percentages of spatial and serial-order trials). In Experiment 2, 'pure' blocks were contrasted to blocks in which spatial and serial-order trials were intermixed with a third task requiring a semantic categorization of sounds. Results from both experiments showed that, whereas serial-order recall is linearly affected by the simultaneous encoding of a concurrent feature, the recall of position is mostly unaffected by concurrent feature encoding. Contrastingly, overall performance level was lower for spatial recall than serial recall. We concluded that serial order and location of items appear to be independently encoded in auditory working memory. Serial order is easier to recall, but strongly affected by the processing of concurrent item dimensions, while item location is more difficult to recall, but relatively automatic, as shown by its strong resistance to interfering dimensions in encoding.     

Serial Order in Spatial Immediate Memory

Serial order effects in spatial memory are investigated in three experiments. In the first an analysis of errors in recall data suggested that immediate transpositions were the most common error and that order errors over 2 or 3 adjacent items accounted for the majority of errors in recall. The first and last serial positions are less error-prone than is the middle position in sets of six and seven items. A second experiment investigated recognition of transpositions and found that immediate transpositions were hardest to recognize but that a traditional serial position effect was not found. This may be due to the difficulty of maintaining one set of spatial items when another set is presented for comparison. A probe experiment, in which subjects were asked to recognize whether a single item came from a memory set and then to assign it to its position in the set indicated that the first and last positions were remembered more accurately than were central positions. The combination of serial order data in recall and position data suggests that there are similarities between serial order and position effects in the verbal and spatial domains and that serial order in spatial sequences is position-based.     

Retention of word pairs as a function of level of processing,instruction to remember,and delay

ABSTRACT

Modern research on the efficacy of levels of processing (LoP) tasks on memory has focused on less than 1-day retention delays, while assuming that the observed benefits of deep tasks will continue across remote delays. However, direct tests of the continued benefits of deep processes for accuracy and organisation in remote memory are rare. The current set of experiments, using auditorily-presented lists of scrambled word pairs, tested whether deep LoP tasks produced better free recall and organisation over one week (Experiment 1) and four weeks (Experiments 2 and 3). All experiments revealed significant LoP effects on free recall and organisation at immediate and delayed test, with no effect of intention to remember. However, Experiments 2 and 3 revealed poor recall and organisation at the delayed tests among all of the LoP groups, suggesting that deep processing may not produce highly accessible memories over very long delays.     

Does test delay eliminate collaborative inhibition?

Earlier research has demonstrated that collaborative groups recall more than individuals, but less than nominal groups (pooled performance of individuals), thus exhibiting collaborative inhibition. In two experiments, all participants were first asked to recall story material on their own. Some participants were then assigned to pairs and recalled the material collaboratively. On the other hand, the participants in the individual recall condition were asked to recall the material once again on their own. In Experiment 1, the collaborative pairs recalled less than the nominal pairs in accordance with previous studies. In Experiment 2, the timing of the initial individual recall was manipulated by inserting one week between the learning and the recall. The collaborative inhibition was eliminated in this situation. Sources of the collaborative inhibition in immediate recall and its disappearance in delayed recall are discussed in terms of the effect of cross cueing in collaborative remembering.     

The influence of acoustic similarity on serial recall of letter sequences

Acoustic similarity is known to impair short-term memory (STM) for letter sequences. The present series of experiments investigated the effects of acoustic similarity on long-term retention. In the first experiment, subjects were asked to learn one of two lists of 8 letters, the letters being either of high or low acoustic similarity. Lists were visually presented for three trials, with subjects responding after each trial. Then subjects participated in an immediate memory task for digits which lasted for 20 min. Finally, subjects tried to recall the list of letters they had learned previously. Lists having items of high acoustic similarity were more difficult to recall on the first trial, but were better recalled on the delayed retention test. In a second experiment, groups of subjects were again asked to learn one of two lists of 8 letters differing in acoustic similarity, using different orders of the letters used previously. The procedures were identical except that in two groups, a STM task for digits intervened between the presentation and test of the letters. This intervening task minimized the effects of STM and eliminated the differences in retention found previously. In a third experiment, better long-term retention for material having high acoustic similarity was also obtained when subjects used a backward recall procedure. In the last experiment 14 item lists were learned to a criterion of two correct trials, and retention was tested after each trial and at a delay of 20 min. and 23 hr. No effect of acoustic similarity was found and little retention loss occurred. These results suggest that reducing the STM component by introducing a STM control or by lengthening the list caused the effect of acoustic similarity to disappear.     

Hippocampal Activations during Repetitive Learning and Recall of Geometric Patterns

Hippocampal activation is required for episodic memory. Encoding and retrieval of novel and memorable items have been related to different locations in the hippocampus; however, the data remain ambiguous. The application of a newly designed keyboard allowed investigation of brain activation during encoding and free immediate and delayed recall with functional magnetic resonance imaging (fMRI) in young healthy controls (n=12). Because of the repetitive learning and recall conditions, an individual learning gradient was used to contrast neural activity at different individual levels of novelty. During learning, subjects were asked to memorize 10 geometric patterns requiring the establishment of intra-item associations for memorization. After learning, subjects were asked to recall the items actively via the keyboard. Learning and recall were alternated five times. Delayed recall was scanned about 15 min after the fifth immediate recall condition without subjects having seen the items again. Left-sided anterior hippocampal activity was observed during conditions of initial learning as well as maximum recall. Neural activity during delayed recall did not reveal hippocampal responses and was characterized by a transition of neural activity from occipitoparietal regions to bilateral temporal cortices. We conclude that both lateralization and segregation depend on the specific relational characteristics of the stimuli requiring establishment of intra-item associations for encoding as well as retrieval. The absence of hippocampal activation during delayed recall together with the increase of lateral temporal involvement possibly corresponds with an emerging transition from episodic to long-term memory.     

Effects of list organization and retrieval cues on children's delayed recall.

Developmental differences in recall were investigated as a function of mode of presentation (blocked vs. random), recall condition (cued vs. noncued), and time of recall (immediate vs. delayed). Ninety-six second graders and 96 fourth graders were the subjects, and the stimuli were 20 pictured items from five categories. Data on three dependent variables (item recall, category recall, and clustering score) were analyzed. Immediate recall was better than delayed recall, the fourth graders' overall performance was superior to that of the second graders, and the blocked presentation of items and the presence of retrieval cues at recall enhanced recall and organization in recall. Furthermore, an analysis of a three-way interaction on two dependent measures indicated that, in the noncued condition, immediate recall was better than delayed recall for children in both grades. However, in the cued condition, the fourth graders performed better during delayed recall than during immediate recall, whereas the second graders did better during immediate recall than during delayed recall.     

Education as a Science

Developmental differences in recall were investigated as a function of mode of presentation (blocked vs. random), recall condition (cued vs. noncued), and time of recall (immediate vs. delayed). Ninety-six second graders and 96 fourth graders were the subjects, and the stimuli were 20 pictured items from five categories. Data on three dependent variables (item recall, category recall, and clustering score) were analyzed. Immediate recall was better than delayed recall, the fourth graders' overall performance was superior to that of the second graders, and the blocked presentation of items and the presence of retrieval cues at recall enhanced recall and organization in recall. Furthermore, an analysis of a three-way interaction on two dependent measures indicated that, in the noncued condition, immediate recall was better than delayed recall for children in both grades. However, in the cued condition, the fourth graders performed better during delayed recall than during immediate recall, whereas the second graders did better during immediate recall than during delayed recall.     

Planning paths to multiple targets: memory involvement and planning heuristics in spatial problem solving

For large numbers of targets, path planning is a complex and computationally expensive task. Humans, however, usually solve such tasks quickly and efficiently. We present experiments studying human path planning performance and the cognitive processes and heuristics involved. Twenty-five places were arranged on a regular grid in a large room. Participants were repeatedly asked to solve traveling salesman problems (TSP), i.e., to find the shortest closed loop connecting a start location with multiple target locations. In Experiment 1, we tested whether humans employed the nearest neighbor (NN) strategy when solving the TSP. Results showed that subjects outperform the NN-strategy, suggesting that it is not sufficient to explain human route planning behavior. As a second possible strategy we tested a hierarchical planning heuristic in Experiment 2, demonstrating that participants first plan a coarse route on the region level that is refined during navigation. To test for the relevance of spatial working memory (SWM) and spatial long-term memory (LTM) for planning performance and the planning heuristics applied, we varied the memory demands between conditions in Experiment 2. In one condition the target locations were directly marked, such that no memory was required; a second condition required participants to memorize the target locations during path planning (SWM); in a third condition, additionally, the locations of targets had to retrieved from LTM (SWM and LTM). Results showed that navigation performance decreased with increasing memory demands while the dependence on the hierarchical planning heuristic increased.     

Can intentional forgetting reduce false memory? Effects of list-level and item-level forgetting

This study examined whether false memory produced by the learning of lists of categorized and associative materials could be reduced by directed forgetting. The number of items within a list that participants were asked to remember or forget was manipulated, while the length of the list remained constant. Experiment 1a used categorized lists and Experiment 1b used associative lists; the participants performed immediate free recall and cued recall tests. For both the categorized and associative lists, the rate of false recall increased upon increasing the proportion of "forget" (F) words. After removing the immediate recall test, Experiment 2 found that intentionally forgetting part of the studied list reduced false memory, whereas forgetting the whole studied list did not. The results are discussed in terms of the list-level-vs.-item-level inhibition in semantic activation and the role of monitoring in reducing false memory.     

Articulatory suppression and the grouping of successive stimuli

Summary Two experiments required subjects to memorise for immediate recall lists of nine items, presented visually and grouped by threes. As each item followed the previous one in the same spatial location, it must have been temporarily stored until the whole group had arrived. In one experiment the items were digits; grouping could be detected by the fact that recall of the last two items in a group was heavily contingent upon recall of the first item. In the second experiment the items were letters, and some of the lists were made up of meaningful triplets of letters such as UNO. Grouping could be detected by the size of the difference between these lists and the meaningless ones. In each experiment, the extent of grouping was just as great if the subjects were asked to repeat an irrelevant sequence of sounds while memorising; although the recall under both conditions was of course depressed.It appears therefore that the temporary memory, in which the items are held before grouping, is not impaired by articulatory suppression; nor in these conditions could it have been a sensory store. The result is supportive evidence for the existence of an abstract, non-sensory, non-motor, working memory.Both authors are employed, and their research supported, by the Medical Research Council     

Spatial clustering and hierarchical coding in immediate serial recall

Four experiments are reported that demonstrate the benefits of clustering by spatial proximity in spatial serial recall and provide support for the notion that hierarchical coding underpins the retention of clustered sequences in spatial working memory. Sequences segregated by spatial clusters increased serial recall performance at different levels of sequence length in a variation of the Corsi test and produced a faster initial response time (RT), which indicates that they afforded data reducing processes. RT at cluster boundary increased in parallel with the number of items forming the clusters, suggesting that subroutines of different length were responsible for the ordering of items within clusters of different size. Evidence for hierarchical coding was also obtained in a serial recognition task, indicating this type of representation pertains to the retention of the sequences rather than exclusively to the organisation of the motor plan for the reproduction of the sequences.     

Need for Cognition and false recall

Two experiments investigated whether Need for Cognition (NFC) affected false recall in the Deese-Roediger-McDermott (DRM) paradigm. In the first experiment, participants were presented with DRM lists and given one attempt to recall the items. In the second experiment, participants were presented with DRM lists under full or divided attention and were given three consecutive recall tests. In Experiment 2, high-NFC individuals exhibited increased false recall across successive recall attempts in both the full and divided attention conditions whereas low-NFC individuals did not. Furthermore, high-NFC individuals in the full attention condition exhibited increased levels of true recall across successive tests. These results show that the individual differences in the ways in which individuals process information can affect true and false recall in the DRM task.     

Short-term memory for spatial and temporal information

Two experiments examined the probed recall of visually presented letter sequences in which the items appeared at different spatial locations. Three types of probe were compared: (1) spatial position; (2) temporal association; and (3) combined position and association. In the first experiment, in which the spatial locations of the items were correlated with their temporal order, spatial probes were more effective than temporal association probes. In the second experiment spatial location was uncorrelated with temporal order, and spatial probes were less effective than temporal association probes. Regardless of the probe, errors tended to be items presented close in time to correct responses: spatial proximity was far less important. The results are discussed in terms of a storage system in which items and their spatial locations are organized within a temporal format. Both experiments showed superior combined probe performance, demonstrating that short-term retrieval is not limited to the use of one type of cue at a time. Secondary aspects of the results showed additionally that subjects can “edit” their responses to avoid making obvious mistakes, and that spatial location can be partially forgotten rather than being completely lost.     

The testing effect in free recall is associated with enhanced organizational processes

In two experiments with categorized lists, we asked whether the testing effect in free recall is related to enhancements in organizational processing. During a first phase in Experiment 1, subjects studied one list over eight consecutive trials, they studied another list six times while taking two interspersed recall tests, and they learned a third list in four alternating study and test trials. On a test 2 days later, recall was directly related to the number of tests and inversely related to the number of study trials. In addition, increased testing enhanced both the number of categories accessed and the number of items recalled from within those categories. One measure of organization also increased with the number of tests. In a second experiment, different groups of subjects studied a list either once or twice before a final criterial test, or they studied the list once and took an initial recall test before the final test. Prior testing again enhanced recall, relative to studying on the final test a day later, and also improved category clustering. The results suggest that the benefit of testing in free recall learning arises because testing creates retrieval schemas that guide recall.     

Time-limited effects of emotional arousal on item and source memory

Two experiments investigated the time-limited effects of emotional arousal on consolidation of item and source memory. In Experiment 1, participants memorized words (items) and the corresponding speakers (sources) and then took an immediate free recall test. Then they watched a neutral, positive, or negative video 5, 35, or 50?min after learning, and 24 hours later they took surprise memory tests. Experiment 2 was similar to Experiment 1 except that (a) a reality monitoring task was used; (b) elicitation delays of 5, 30, and 45?min were used; and (c) delayed memory tests were given 60?min after learning. Both experiments showed that, regardless of elicitation delay, emotional arousal did not enhance item recall memory. Second, both experiments showed that negative arousal enhanced delayed item recognition memory only at the medium elicitation delay, but not in the shorter or longer delays. Positive arousal enhanced performance only in Experiment 1. Third, regardless of elicitation delay, emotional arousal had little effect on source memory. These findings have implications for theories of emotion and memory, suggesting that emotion effects are contingent upon the nature of the memory task and elicitation delay.     

Interference in immediate spatial memory

It has been suggested that maintenance in visuospatial immediate memory involves implicit motor processes that are analogous to the articulatory loop in verbal memory. An alternative account, which is explored here, is that maintenance is based on shifts of spatial attention. In four experiments, subjects recalled spatial memory span items after an interval, and in a fifth experiment, digit span was recalled after an interval. The tasks carried out during the interval included touching visual targets, repeating heard words, listening to tones from spatially sepa-rated locations, pointing to these tones, pointing to visual targets, and categorizing spatial tar-gets as being from the left or right. Spatial span recall was impaired if subjects saw visual tar-gets or heard tones, and this impairment was increased if either a motor response or a categorical response was made. Repeating words heard in different spatial locations did not impair recall, but reading visually presented words did interfere. For digit span only, the tasks involving a verbal response impaired recall. The results are interpreted within a framework in which active spatial attention is involved in maintaining spatial items in order in memory, and is interfered with by any task (visual, auditory, perceptual, motor) that also makes demands on spatial attention.