Effects of environmental support on overt and covert visuospatial rehearsal

People can rehearse to-be-remembered locations either overtly, using eye movements, or covertly, using only shifts of spatial attention. The present study examined whether the effectiveness of these two strategies depends on environmental support for rehearsal. In Experiment 1, when environmental support (i.e., the array of possible locations) was present and participants could engage in overt rehearsal during retention intervals, longer intervals resulted in larger spans, whereas in Experiment 2, when support was present but participants could only engage in covert rehearsal, longer intervals resulted in smaller spans. When environmental support was absent, however, longer retention intervals resulted in smaller memory spans regardless of which rehearsal strategies were available. In Experiment 3, analyses of participants’ eye movements revealed that the presence of support increased participants’ fixations of to-be-remembered target locations more than fixations of non-targets, and that this was associated with better memory performance. Further, although the total time fixating targets increased, individual target fixations were actually briefer. Taken together, the present findings suggest that in the presence of environmental support, overt rehearsal is more effective than covert rehearsal at maintaining to-be-remembered locations in working memory, and that having more time for overt rehearsal can actually increase visuospatial memory spans.     

Ontogeny of early event memory: I. Forgetting and retrieval by 2- and 3-month-olds

In 2 experiments, 2-month-olds, trained in the mobile conjugate reinforcement paradigm for two daily sessions, showed retrieval deficits relative to 3-month-olds. In Experiment 1, tests of simple forgetting administered to 2-month-olds after retention intervals of 1, 3, 6, and 9 days (a period over which 3-month-olds remember the contingency) indicated that their forgetting was complete after delays greater than 1 day. In Experiment 2, reactivation treatments administered to 2- and 3-month-olds alleviated forgetting after a retention interval of 28, but not 35, days in the 3-month-old group only. Previously, alleviated forgetting by a reactivation treatment had been demonstrated in 2-month-olds after a delay of 18 days. In both of the present experiments, performance of the two age groups did not differ during the immediate retention test at the end of training. These results suggest that neither the age of the infant nor the age of the memory determines memory retrieval after long delays; instead, it appears to be determined by the length of time that a memory has been inaccessible (i.e., forgotten). We propose that factors which delay simple forgetting will correspondingly increase the length of the interval over which a retrieval cue can still be effective in a reactivation paradigm, irrespective of the age of the infant or the age of the memory.     

Long-term memory,forgetting, and deferred imitation in 12-month-old infants

Long-term recall memory, as indexed by deferred imitation, was assessed in 12-month-old infants. Independent groups of infants were tested after retention intervals of 3 min, 1 week and 4 weeks. Deferred imitation was assessed using the ‘observation-only’ procedure in which infants were not allowed motor practice on the tasks before the delay was imposed. Thus, the memory could not have been based on re-accessing a motor habit, because none was formed in the first place. After the delay, memory was assessed either in the same or a different environmental context from the one in which the adult had originally demonstrated the acts. In Experiments 1 and 3, infants observed the target acts while in an unusual environment (an orange and white polka-dot tent), and recall memory was tested in an ordinary room. In Experiment 2, infants observed the target acts in their homes and were tested for memory in a university room. The results showed recall memory after all retention intervals, including the 4 week delay, with no effect of context change. Interestingly, the forgetting function showed that the bulk of the forgetting occurred during the first week. The findings of recall memory without motor practice support the view that infants as young as 12 months old use a declarative (nonprocedural) memory system to span delay intervals as long as 4 weeks.     

Forgetting in spatial memories acquired in a virtual environment

This study examined forgetting in spatial memories acquired in a virtual environment. In the two experiments, participants learned the locations of eight objects. In Experiment 1, the objects were presented as photographs in either a laboratory or in an equivalent virtual environment. Irrespective of learning condition, accuracy of recall of the locations was found to deteriorate after a retention interval of approximately 1 week. In Experiment 2, following virtual learning, three groups of participants performed a series of non‐spatial tasks of low, intermediate or high difficulty. The tasks were presented in a retention interval of 2 hours. A comparison of recall accuracy before and after presentation of the interference tasks indicated that that the groups were not differentially affected by the difficulty of the retroactive interference tasks. However, the groups differed in their subjective assessment of the mental workload involved in the tasks. The results are discussed with reference to a prominent theory of forgetting. Copyright © 2007 John Wiley & Sons, Ltd.     

The contribution of disengagement to temporal discriminability

The present study examines the idea that time-based forgetting of outdated information can lead to better memory of currently relevant information. This was done using the visual arrays task, along with a between-subjects manipulation of both the retention interval (1?s vs. 4?s) and the time between two trials (1?s vs. 4?s). Consistent with prior work [Shipstead, Z., &; Engle, R. W. (2013). Interference within the focus of attention: Working memory tasks reflect more than temporary maintenance. Journal of Experimental Psychology: Learning, Memory, and Cognition, 39, 277–289; Experiment 1], longer retention intervals did not lead to diminished memory of currently relevant information. However, we did find that longer periods of time between two trials improved memory for currently relevant information. This replicates findings that indicate proactive interference affects visual arrays performance and extends previous findings to show that reduction of proactive interference can occur in a time-dependent manner.     

Looking forward: the effects of photographs on the qualities of future thinking

Future episodic thinking relies on the reconstruction of remembered experiences. Photographs provide one means of remembering, acting as a “cognitive springboard” for generating related memory qualities. We wondered whether photographs would also invite embellishment of future thought qualities, particularly in the presence (or absence) of associated memories. In two studies participants generated future events in familiar (associated memories) and novel (no associated memories) locations. Half of the participants viewed scene location photographs during event generation. All participants then imagined the events for one minute and completed a self-report measure of content qualities. Results of the current set of studies suggested that for novel locations, no differences in qualities emerged; however, for familiar locations, photographs did not enhance qualities and, in some cases, actually constrained perceptual (Experiments 1 and 2) and sensory (Experiment 1) detail ratings of future thoughts. Thus, photographs did not invite embellishment of future thought details.     

Time-dependent forgetting in visual short-term memory

ABSTRACT

Whether visual short-term memory can be lost over an unfilled delay, in line with time-dependent forgetting, is controversial and prior work has yielded mixed results. The present study explored time-dependent forgetting in visual short-term memory in relation to other factors. In three experiments, participants compared single target and probe objects over a 2 s or 10 s retention interval. The objects across trials were either similar or dissimilar (Experiment 1) and had to be remembered in the presence of an additional distractor (Experiment 2) or under conditions where the amount of time separating trials varied (Experiment 3). In all experiments, the retention interval manipulation made the biggest contribution to performance, with accuracy decreasing as the retention interval was lengthened from 2 s to 10 s. These results pose problems for interference and temporal distinctiveness models of memory but are compatible with temporal forgetting mechanisms such as decay.     

Are Asians forgetful? Perception, retention, and recall in episodic remembering

Cross-cultural studies have shown that Asians exhibit less accessibility to episodic memories than Euro-Americans. This difference is often attributed to differential cognitive and social influences on memory retention, although there have been no empirical data concerning the underlying mechanism. Three studies were conducted to examine encoding and retention processes that may underlie the cultural difference in episodic recall. While Asians recalled fewer personal event episodes than Euro-Americans across different retention intervals, the two groups showed similar forgetting functions over time (Study 1). Asians also recalled fewer episodes of fictional events than Euro-Americans when the retention interval was kept to a minimum (Study 2). Finally, Asians perceived fewer discrete episodes than Euro-Americans when reading events in a narrative text (Study 3). Collectively, these findings suggest that the cultural difference in episodic recall may not be a mere consequence of memory retention but culture-specific perceptual processing and encoding. They have great theoretical, developmental, and clinical relevance.     

Faster forgetting contributes to impaired spatial memory in the PDAPP mouse: Deficit in memory retrieval associated with increased sensitivity to interference?

Two experiments were conducted to investigate the possibility of faster forgetting by PDAPP mice (a well-established model of Alzheimer's disease as reported by Games and colleagues in an earlier paper). Experiment 1, using mice aged 13-16 mo, confirmed the presence of a deficit in a spatial reference memory task in the water maze by hemizygous PDAPP mice relative to littermate controls. However, after overtraining to a criterion of equivalent navigational performance, a series of memory retention tests revealed faster forgetting in the PDAPP group. Very limited retraining was sufficient to reinstate good memory in both groups, indicating that their faster forgetting may be due to retrieval failure rather than trace decay. In Experiment 2, 6-mo-old PDAPP and controls were required to learn each of a series of spatial locations to criterion with their memory assessed 10 min after learning each location. No memory deficit was apparent in the PDAPP mice initially, but a deficit built up through the series of locations suggestive of increased sensitivity to interference. Faster forgetting and increased interference may each reflect a difficulty in accessing memory traces. This interpretation of one aspect of the cognitive deficit in human mutant APP mice has parallels to deficits observed in patients with Alzheimer's disease, further supporting the validity of transgenic models of the disease.     

Differential time-dependent effects of emotion on recollective experience and memory for contextual information

Emotion has been suggested to slow forgetting via a mechanism that enhances memory consolidation. Here, we investigate whether this time dependent process influences the subjective experience of recollection as well as the ability to retrieve specific contextual details of the study event. To do so we examined recognition for emotional and neutral pictures at two retention intervals and collected remember/know reports and reports about the task that had been performed with the item during encoding. Recollective experience was enhanced for emotional compared to neutral photos after a 24-h delay, but not immediately after encoding. In contrast, memory for the task performed during encoding did not differ between emotional and neutral photos at either time point. The findings indicate that emotion slows the effects of forgetting on the recollective experience associated with studied events, without necessarily slowing the forgetting of specific contextual details of those events.     

Need probability affects retention: A direct demonstration

Recent memory theory has emphasized the concept ofneed probability—that is, the probability that a given piece of learned information will be tested at some point in the future. It has been proposed that, in real-world situations, need probability declines over time and that the memory-loss rate is calibrated to match the progressive reduction in need probability (J. R. Anderson & Schooler, 1991). The present experiments were designed to examine the influence of the slope of the need-probability curve on the slope of the retention curve. On each of several trials, subjects memorized a list of digits, then retained the digits in memory for 1, 2, 4, 8, or 16 sec. Some trials ended with a recall test; other trials ended with the message, “no test.” In Experiment 1, the likelihood of encountering a memory test (i.e., the need probability) was made to either increase or decrease as the retention interval increased; in Experiment 2, need probability either was flat (invariant across retention intervals) or decreased as the retention interval increased. The results indicated that the shape of the need-probability curve influenced the slope of the retention curve (Experiment 1) and that the effect became larger as the experimental session progressed (Experiment 2). The findings support the notion that memory adapts to need probabilities and that the rate of forgetting is influenced by the slope of the need-probability curve. In addition, all of the forgetting curves approximated a power function, suggesting that need probability influences the slope but not the form of forgetting.     

A test of the reward-value hypothesis

Rats retain source memory (memory for the origin of information) over a retention interval of at least 1 week, whereas their spatial working memory (radial maze locations) decays within approximately 1 day. We have argued that different forgetting functions dissociate memory systems. However, the two tasks, in our previous work, used different reward values. The source memory task used multiple pellets of a preferred food flavor (chocolate), whereas the spatial working memory task provided access to a single pellet of standard chow-flavored food at each location. Thus, according to the reward-value hypothesis, enhanced performance in the source memory task stems from enhanced encoding/memory of a preferred reward. We tested the reward-value hypothesis by using a standard 8-arm radial maze task to compare spatial working memory accuracy of rats rewarded with either multiple chocolate or chow pellets at each location using a between-subjects design. The reward-value hypothesis predicts superior accuracy for high-valued rewards. We documented equivalent spatial memory accuracy for high- and low-value rewards. Importantly, a 24-h retention interval produced equivalent spatial working memory accuracy for both flavors. These data are inconsistent with the reward-value hypothesis and suggest that reward value does not explain our earlier findings that source memory survives unusually long retention intervals.     

Dissociating familiarity from recollection in human recognition memory: Different rates of forgetting over short retention intervals

Two functionally distinct forms of recognition memory have been identified in human and nonhuman species—the ability to recollect qualitative information about previous events, and the ability to differentiate between familiar and novel stimuli. Separate dual-process theories have been developed in the animal and human literatures to account for these findings. However, it is not clear whether these theories describe the same two underlying memory processes. On the basis of animal studies of medial temporal lobe function, familiarity is expected to exhibit disproportionately fast forgetting compared with recollection over short retention intervals. We tested this prediction in healthy human subjects by examining recognition forgetting rates across a range of 8–32 intervening items and found significant forgetting in the accuracy of familiarity-based discriminations and no evidence of forgetting in the accuracy of recollection-based discriminations. In agreement with the results from nonhuman species, the present results indicate that item familiarity decreases more rapidly than recollection over short retention intervals.     

Short-term memory for temporal intervals: Contrasting explanations of the choose-short effect in pigeons

To better understand short-term memory for temporal intervals, we re-examined the choose-short effect. In Experiment 1, to contrast the predictions of two models of this effect, the subjective shortening and the coding models, pigeons were exposed to a delayed matching-to-sample task with three sample durations (2, 6 and 18 s) and retention intervals ranging from 0 to 20 s. Consistent with the coding model, the results suggested a sudden forgetting of memories for duration. In Experiment 2, to test the confusion hypothesis, the characteristics of the ITI and the retention interval differed. Contrary to the confusion hypothesis, a choose-short effect was obtained. In both experiments, a test with only two of the three comparison keys was performed. The results suggest three effects that may be controlling the birds’ responses: stimulus generalization when no retention interval is present; an increase in random responding at longer retention intervals; and, similarly, an increase in preference for the “short-sample” key at longer retention intervals.     

Forgetting is effortful: Evidence from reaction time probes in an item-method directed forgetting task

Reaction time (RT) was measured in response to visual detection probes embedded within an item-method directed forgetting paradigm. In Experiment 1, study words were presented individually followed by an instruction to remember (R) or forget (F). Probes were presented at stimulus onset asynchronies (SOAs) of 1,400, 1,800, or 2,600 msec in relation to the study word or memory instruction. After the study trials, a yes-no recognition task measured retention of R and F words. Experiment 2 added a no-word control condition and no-probe catch trials. In both experiments, post-F probe RTs were longer than post-R probe RTs at early SOAs. Confirming that participants attended to the memory instructions, there was a significant directed forgetting effect, with greater recognition of R than of F words. These findings contradict the view that directed forgetting in the item-method paradigm is due to the passive decay of nonrehearsed F items; instead, they are consistent with the view that intentional forgetting in an item-method paradigm occurs via the operation of an active, potentially inhibitory, cognitive process.     

Spatio-temporal working-memory and short-term object-location tasks use different memory mechanisms

Spatial short-term memory for objects' locations was investigated in a spatial relocation task. During maintenance, dynamic visual noise or spatial tapping were administered as visual or spatial secondary tasks, respectively. Because memory for location should tap the visual component of working memory, a visual but not a spatial secondary task should impair location memory. In fact, neither of the tasks impaired memory (Experiment 1), although the expected dissociation between visual and spatial components was clearly confirmed for a spatio-temporal main task (Corsi test) (Experiment 2). We then contrasted location memory for pictures of objects and of nonsense figures under visual interference. Real objects were relocated much better than nonsense figures, and visual noise was again ineffective (Experiment 3). When spatial tapping was combined with the same material (Experiment 3a), again no influence on memory for locations of objects was observed and only a small influence on remembering nonsense figures. We suggest that the Corsi and the relocation VSWM-tasks use different memory mechanisms. The configuration of objects is reconstructed from perceptual records in an episodic buffer, provided by the same structures that enable visual memory after longer intervals. Rehearsal is not necessary for the persistence of these traces. In contrast, in the Corsi task remembering, a temporal sequence across homogeneous locations needs spatio-temporal marking and therefore active rehearsal of the locations by shifting spatial attention. A spatially demanding secondary task during retention interrupts this rehearsal.     

Effects of pointing compared with naming and observing during encoding on item and source memory in young and older adults

Research showed that source memory functioning declines with ageing. Evidence suggests that encoding visual stimuli with manual pointing in addition to visual observation can have a positive effect on spatial memory compared with visual observation only. The present study investigated whether pointing at picture locations during encoding would lead to better spatial source memory than naming (Experiment 1) and visual observation only (Experiment 2) in young and older adults. Experiment 3 investigated whether response modality during the test phase would influence spatial source memory performance. Experiments 1 and 2 supported the hypothesis that pointing during encoding led to better source memory for picture locations than naming or observation only. Young adults outperformed older adults on the source memory but not the item memory task in both Experiments 1 and 2. In Experiments 1 and 2, participants manually responded in the test phase. Experiment 3 showed that if participants had to verbally respond in the test phase, the positive effect of pointing compared with naming during encoding disappeared. The results suggest that pointing at picture locations during encoding can enhance spatial source memory in both young and older adults, but only if the response modality is congruent in the test phase.     

From A to Z? Retrieval-induced forgetting of non-verbal information indicates how writing systems can shape memory organisation

We investigated retrieval-induced forgetting of motor sequences in samples of Chinese participants. Retrieval-induced forgetting occurs when selective retrieval of a subset of information stored in memory causes forgetting for the non-retrieved rest. This phenomenon critically depends on the organised storage of separate categories of memory representations. In studies with participants from a Western culture (Germany), a categorization in left- and right-hand movements previously had been supported by letter stimuli based on a spatial mental representation of the Roman alphabet. The same assignment of letters from the beginning or end of the alphabet to motor sequences performed either with the left- or the right-hand did not entail retrieval-induced forgetting in the present study, however (Experiment 1). In Experiment 2, visual features of displaying to-be-learned sequences additionally supported a distinction into left and right. In Experiment 3, learning trials provided verbal category labels. The occurrence of retrieval-induced forgetting in the latter two experiments suggests language-dependent organisation of non-verbal items in memory.     

Withdrawal of spatial overt attention following intentional forgetting: evidence from eye movements

Eye movements were measured to examine whether item-method directed forgetting involved a spatial overt attention shift. Experiment 1 showed that participants’ eyes were moved away from the study word following the forget and ignore cues, but not the remember cue. Experiment 2 revealed that the eyes were moved away from the area that covered by the study word even when the study word disappeared upon the presentation of the memory cue. Both the study word and memory cue were presented auditorily in Experiment 3. In all experiments, the to-be-remembered words were recalled better than both to-be-forgotten and to-be-ignored words. More importantly, mental effort, as indexed by the pupil size, increased following the remember, as compared with the forget and ignore cues. These findings are discussed in terms of controlling spatial overt attention after encoding to withdraw attention from irrelevant information and to allocate cognitive resources to relevant information for long-term retention.     

负性情绪材料的定向遗忘及心理机制

采用项目法定向遗忘的研究范式,在两个实验中分别采用文字和图片材料考察了情绪性记忆定向遗忘的效果及其心理机制。实验中采用了中性和负性两种实验材料,设置了两种记忆指令出现时间（2秒后提示和5秒后提示）,相对于中性材料,被试更不容易忘记负性材料。记忆指令出现的时间只影响图片材料的定向遗忘。研究表明负性情绪会干扰定向遗忘,选择性编码理论可以解释情绪性文字材料的定向遗忘,而抑制理论更能解释情绪性图片材料的定向遗忘效应。