Remembering can cause forgetting--but not in negative moods

Repeated retrieval of a subset of previously observed events can cause forgetting of the non-retrieved events. We examined how affective states experienced during retrieval modulate such retrieval-induced forgetting by inducing positive, negative, and neutral moods in subjects immediately before they attempted to retrieve studied items. On the basis of recent work, we hypothesized that positive moods encourage relational processing, which should increase interference from related events and thus enhance retrieval-induced forgetting. By contrast, negative moods should encourage item-specific processing, which should reduce interference and thus reduce such forgetting. Our results are consistent with these predictions. When subjects were in negative moods, repeated retrieval did not cause forgetting of the non-retrieved material, whereas when subjects were in positive and neutral moods, they showed reliable retrieval-induced forgetting. Our findings suggest that the emotions involved during interrogation of a witness can affect the result of repeated interrogations.     

Manipulation of the apparatus and response context may reduce the US pre-exposure interference effect

In two experiments, we investigated whether manipulations of associations formed between the context and unconditioned stimulus (US) during exposure would reduce the retardation of future conditioning produced by exposure to the US. In the first experiment, we found that extinguishing the context reduced fear of the context and partially attenuated interference with future conditioning. This attenuation was only transient and there was considerable interference which was unaffected by extinction. In the second experiment, we found that signalling the US during pre-exposure which was carried out off-baseline did not reduce interference when conditioning was also carried out off-baseline. However, signalling the US did reduce interference when conditioning was subsequently continued on-baseline. These results suggest that although the US interference effect is partly mediated by conditioning of the context, it may also depend on learning about the unpredictability of the US during exposure, and some long-term, perhaps context specific, adaption-like mechanism.     

Wakeful rest alleviates interference-based forgetting

Retroactive interference (RI)—the disruptive influence of events occurring after the formation of a new memory—is one of the primary causes of forgetting. Placing individuals within an environment that postpones interference should, therefore, greatly reduce the likelihood of information being lost from memory. For example, a short period of wakeful rest should diminish interference-based forgetting. To test this hypothesis, participants took part in a foreign language learning activity and were shown English translations of 20 Icelandic words for immediate recall. Half of the participants were then given an 8-min rest before completing a similar or dissimilar interfering distractor task. The other half did not receive a rest until after the distractor task, at which point interference had already taken place. All participants were then asked to translate the Icelandic words for a second time. Results revealed that retention was significantly worse at the second recall test, but being allowed a brief rest before completing the distractor task helped reduce the amount of forgetting. Taking a short, passive break can shield new memories from RI and alleviate forgetting.     

Rate of acquisition, adult age, and basic cognitive abilities predict forgetting: new views on a classic problem

Rate of forgetting is putatively invariant across individuals, sharing few associations with individual-differences variables known to influence encoding and retrieval. This classic topic in learning and memory was revisited using a novel statistical application, multilevel modeling, to examine whether (a) slopes of forgetting varied across individuals and (b) observed individual differences in forgetting shared systematic relations with adult age, learning speed, and cognitive ability. Participants (N = 136) received mnemonic training prior to memorizing 4-digit numbers to perfection, and retention was tested immediately after training and after 30 min, 24 hr, 7 weeks, and 8 months. Slower rate of learning to criterion, older age, and poorer cognitive performance predicted accelerated forgetting with associations most pronounced within 24 hr from baseline. Observed correlates of differential forgetting slopes are similar to those previously found to affect encoding, suggesting continuity rather than asymmetry of prediction for these memory processes.     

The effects of interference and retention delay on temporal generalization performance

This study investigated the effect of forgetting of the standard duration on temporal discrimination in a generalization task. In two experiments, participants were given a temporal generalization task with or without a retention delay between the learning of the standard duration and the testing of the comparison durations. During this delay, they either performed or did not perform an interference task. Results failed to reveal any effect of 15-min and 24-h retention delays on time judgments (Experiment 1). However, when an interference task was performed during the 15-min delay (Experiment 2), there was a subjective shortening effect, indicating that the standard duration was judged shorter with than without an interference task. These findings suggest that when an interference task occurs immediately after initial temporal encoding, it affects the process of consolidation in reference memory.     

延时间隔和线索类型对遗忘学习判断的影响*

主要探讨不同延时间隔和线索类型对遗忘元认知判断的影响。采用传统的学习判断任务,让被试学习40对无意义配对词,并告知随后进行测试,当呈现第一个词时,被试能够回忆与之配对的后一个词。让被试预测当延迟不同时间（5分钟、1天和1周）进行测试时,他们能够记住（学习判断）或者遗忘（遗忘判断）后一词的可能性。最后,要求被试回忆所有词对。结果发现延时间隔对学习判断和遗忘判断有相似的影响;学习判断的等级和相对准确性均高于遗忘判断,说明人们对记住和遗忘的线索很敏感;相比于学习判断,人们监测自己遗忘能力的信心不足。研究结果表明人们能够利用延时间隔和线索类型来预测未来的测验成绩,对遗忘的监测能力低于对记住的监测。     

Influence of a depressant drug on acquisition in rote learning

Central depressant drugs have been shown to impair performance during learning and at recall. The experiment which is described was carried out to investigate whether the effect during learning is primarily on the availability of associations or on their formation. The learning decrement attributable to the drug used (30 per cent. nitrous oxide in oxygen) persisted on recovery from the drug and during subsequent learning under normal conditions. It is concluded that the effect of the drug is on acquisition rather than performance; that is, it acts so as to impede the formative process and does not merely obscure the progress of learning by blocking responses.     

Positional cues in serial learning: The spin-list technique

To test the hypothesis that serial learning depends largely on the encoding and retrieval of position-to-item associations, we examined whether people can learn spin lists on which starting position is randomly varied across successive learning trials. By turning positional information from a reliable cue into a source of intertrial interference, we expected learning to be greatly impaired. Contrary to this hypothesis, we found that participants were only slightly worse at serial learning under spin conditions and that this impairment reflects a substantial increase in initiation errors coupled with a small increase in intertrial forgetting. These data show that participants can effectively use nonpositional cues when positional cues are unreliable.     

Retrieval practice can eliminate list method directed forgetting

It has recently been shown that retrieval practice can reduce memories’ susceptibility to interference, like retroactive and proactive interference. In this study, we therefore examined whether retrieval practice can also reduce list method directed forgetting, a form of intentional forgetting that presupposes interference. In each of two experiments, subjects successively studied two lists of items. After studying each single list, subjects restudied the list items to enhance learning, or they were asked to recall the items. Following restudy or retrieval practice of list 1 items, subjects were cued to either forget the list or remember it for an upcoming final test. Experiment 1 employed a free-recall and Experiment 1 a cued-recall procedure on the final memory test. In both experiments, directed forgetting was present in the restudy condition but was absent in the retrieval-practice condition, indicating that retrieval practice can reduce or even eliminate this form of forgetting. The results are consistent with the view that retrieval practice enhances list segregation processes. Such processes may reduce interference between lists and thus reduce directed forgetting.     

Competition between two memory traces for long-term recognition memory

Previous studies investigating the processes which underlie memory consolidation focused almost exclusively on isolated learning events. Here I studied the competition of two similar memory traces for consolidation non-conditioned recognition memory in adult male C57BL/6JOlaHsd mice using the olfactory cues based social discrimination procedure. My results show that the interference phenomena that cause forgetting are time-dependent, and that retroactive interference can be discriminated from proactive interference. Furthermore, both types of interference can be suppressed by subcutaneous anisomycin treatment immediately after presentation of the interference stimulus. These findings imply that interference phenomena, which result from the competition of two similar memory traces for long-term recognition memory, are related to the progress of memory consolidation and linked to protein synthesis.     

Cognitive control of familiarity: Directed forgetting reduces proactive interference in working memory

Proactive interference (PI) occurs when previously learned information interferes with new learning. In a working memory task, PI induces longer response times and more errors to recent negative probes than to new probes, presumably because the recent probe’s familiarity invites a “yes” response. Warnings, longer intertrial intervals, and the increased contextual salience of the probes can reduce but not eliminate PI, suggesting that cognitive control over PI is limited. Here we tested whether control exerted in the form of intentional forgetting performed during working memory can reduce the magnitude of PI. In two experiments, participants performed a working memory task with directed-forgetting instructions and the occasional presentation of recent probes. Surprise long-term memory testing indicated better memory for to-be-remembered than for to-be-forgotten items, documenting the classic directed-forgetting effect. Critically, in working memory, PI was virtually eliminated for recent probes from prior to-be-forgotten lists, as compared to recent probes from prior to-be-remembered lists. Thus cognitive control, when executed via directed forgetting, can reduce the adverse and otherwise persistent interference from familiarity, an effect that we attribute to attenuated memory representations of the to-be-forgotten items.     

The role of outcome inhibition in interference between outcomes: A contingency‐learning analogue of retrieval‐induced forgetting

Current associative theories of contingency learning assume that inhibitory learning plays a part in the interference between outcomes. However, it is unclear whether this inhibitory learning results in the inhibition of the outcome representation or whether it simply counteracts previous excitatory learning so that the outcome representation is neither activated nor inhibited. Additionally, these models tend to conceptualize inhibition as a relatively transient and cue‐dependent state. However, research on retrieval‐induced forgetting suggests that the inhibition of representations is a real process that can be relatively independent of the retrieval cue used to access the inhibited information. Consistent with this alternative view, we found that interference between outcomes reduces the retrievability of the target outcome even when the outcome is associated with a novel (non‐inhibitory) cue. This result has important theoretical implications for associative models of interference and shows that the empirical facts and theories developed in studies of retrieval‐induced forgetting might be relevant in contingency learning and vice versa.     

合作学习情境下监控者监控发音任务中的定向遗忘效应

在以构建留学生的汉字语音库为共同目标的合作学习情境下,考察了合作学习中的监控者是否会表现出定向遗忘效应。实验一中,协助者朗读两字表的单字并接受定向遗忘或记忆字表中单字的指令;监控者监控发音的流畅性或准确性,并单独接受再认测验;实验二在协助者重新朗读单字的条件下监控者接受再认测验。结果发现:(1)实验一中,监控者只在深层监控发音准确性的任务时,再认成绩表现出定向遗忘效应,浅层监控发音流畅性的任务中未表现出定向遗忘效应;(2)实验二中在测验阶段复原学习情境后,深浅监控任务下的再认成绩虽存在显著差异,但定向遗忘效应也消失了。综合两个实验表明,合作学习情境下,非有意遗忘的监控者的定向遗忘效应与监控任务深度和学习情境复原与否存在密切联系。     

Neurogenesis interferes with the retrieval of remote memories: Forgetting in neurocomputational terms

In contrast to models and theories that relate adult neurogenesis with the processes of learning and memory, almost no solid hypotheses have been formulated that involve a possible neurocomputational influence of adult neurogenesis on forgetting. Based on data from a previous study that implemented a simple but complete model of the main hippocampal circuitry (Weisz & Argibay, 2009), we now test this model under different situations to better study the case of remote memories. The results of this work show that following neurogenesis, the new, ongoing memories in the hippocampus are better retained than when no neurogenesis occurs at all, while the older memories are affected (to a lesser extent) by a special type of interference that is different from interference that occurs with an increasing number of memories per se. This work adds a new point of analysis in support of the interference view that might lead to the forgetting of memories in the hippocampus as they are transferred to neocortex for long-term storage, consistent with the Complementary Learning Systems models of system-level consolidation. Attention should be directed to the specific causes of interference; the results of this work signal a type of distortion of remote memories that is produced by the birth and the growth of new processing units, which results in a subtly impoverished retrieval as new neurons become active. The proposals of this model fit well with some empirical findings that are related to the issue. In the future, as new evidence emerges, we believe that this biological process, which is largely related to learning and memory, will also help to shape our ideas about normal forgetting and its possible contributions to system consolidation.     

Recognition memory for briefly presented pictures: the time course of rapid forgetting

When viewing a rapid sequence of pictures, observers momentarily understand the gist of each scene but have poor recognition memory for most of them (M. C. Potter, 1976). Is forgetting immediate, or does some information persist briefly? Sequences of 5 scenes were presented for 173 ms/picture; when yes-no testing began immediately, recognition was initially high but declined markedly during the 10-item test. With testing delays of 2 or 6 s, the decline over testing was less steep. When 10 or 20 pictures were presented, there was again a marked initial decline during testing. A 2-alternative forced-choice recognition test produced similar results. Both the passage of time and test interference (but not presentation interference) led to forgetting. The brief persistence of information may assist in building a coherent representation over several fixations.     

Context-dependent impairment of recollection in list-method directed forgetting

In list-method directed forgetting, people's ability to forget one of the sets of learned material is examined. Research shows that memory for to-be-forgotten items is impaired when assessed by a recall test and by recognition tests reliant on recollective processes. Retrieval inhibition and context-change mechanisms have been proposed to account for the directed forgetting effects and both of them account for the results obtained with recognition tests. However, the context change account makes a specific prediction that recollection is impaired by directed forgetting only if it makes use of contextual associations. In the present study, directed forgetting was examined with two types of recollection-based tasks making use of different types of associations, namely a list discrimination task utilising contextual associations and an associative recognition task utilising interitem associations. Consistent with the context change account, the costs of directed forgetting were observed in a list discrimination task and were not observed in an associative recognition task. The results indicate that impairment in recollection due to directed forgetting is not general and provide converging evidence to support the context-change account.     

The interval between the CS and the UCS as a determiner of generalization performance

Rats were trained in a conditioned taste aversion paradigm in order to determine whether a trace interval between the conditioned stimulus (CS) and the unconditioned stimulus (UCS) would result in the forgetting of stimulus attributes. Accordingly, subjects were conditioned with milk (CS), given either an immediate or a delayed injection of lithium chloride (UCS), and tested 48 h later with either milk or chocolate milk, a generalized flavor. The rats conditioned immediately following the presentation of the CS avoided milk more than chocolate milk, indicating discrimination between the two flavors. Those conditioned after a trace interval avoided both flavors equally, suggesting a loss of stimulus attributes of the original CS. Delay rats, however, still exhibited substantial learning when compared with controls not experiencing the UCS. These results allege a role for the forgetting of stimulus attributes during a trace interval in addition to following a complete learning episode.     

Destructive effects of “forget” instructions

In two experiments, participants were given three lists of words to study and were told to (1) remember all three lists, (2) forget the first list immediately after studying it but try to remember the other two lists, or (3) forget the middle list immediately after studying it but try to remember the first and the last lists. In Experiment 1, unrelated word lists were used, whereas Experiment 2 replicated Experiment 1 with categorical lists. The results from both experiments showed that forgetting the middle list leads also to recall decrement for the first list, which was not intended for forgetting. The results are discussed in terms of the contextual change hypothesis of directed forgetting.     

Effects of nitrous oxide on reactions to “stress”

It has been demonstrated that exposure to the stress of a situation involving conflict or frustration may interfere significantly with subsequent learning. Behaviour under stress is characterized by experiences of “anxiety” and by widespread physiological changes. Inhalation of nitrous oxide has the general effect of reducing the extent of these symptoms.

The present investigation using insoluble and soluble problems has demonstrated that both nitrous oxide and exposure to stress impair learning; but that, when subjects are exposed to stress while under the influence of the drug, the effects of the stress on subsequent learning are abolished. It is suggested that these empirical results may be accounted for either in terms of “anxiety-reduction” or in terms of transfer effects.     

The influence of directional associations on directed forgetting and interference

Two experiments examined how cross-list directional associations influenced list-method directed forgetting and the degree of interference observed on each list. Each List 1 item had a (a) bidirectionally related item on List 2 (chip <----> potato), (b) forward association with an item on List 2 (chip --> wood), (c) backward association from an item on List 2 (chip <-- chisel), or (d) no relationship with List 2 items. The results revealed that associative relationships that eliminated retroactive interference in the baseline condition also eliminated the directed forgetting costs. In contrast, associative relationships did not affect List 2 recall in the forget group, which remained unchanged across experimental conditions. However, certain conditions reduced proactive interference in the remember group, thereby eliminating the benefits of directed forgetting. The directed forgetting costs and benefits were observed independently of each other. The authors propose that these effects emerged from a combination of item and context strengthening induced by different associative directions.