New in, old out: Does learning a new language make you forget previously learned foreign languages?

Anecdotal evidence suggests that learning a new foreign language (FL) makes you forget previously learned FLs. To seek empirical evidence for this claim, we tested whether learning words in a previously unknown L3 hampers subsequent retrieval of their L2 translation equivalents. In two experiments, Dutch native speakers with knowledge of English (L2), but not Spanish (L3), first completed an English vocabulary test, based on which 46 participant-specific, known English words were chosen. Half of those were then learned in Spanish. Finally, participants' memory for all 46 English words was probed again in a picture naming task. In Experiment 1, all tests took place within one session. In Experiment 2, we separated the English pre-test from Spanish learning by a day and manipulated the timing of the English post-test (immediately after learning vs. 1 day later). By separating the post-test from Spanish learning, we asked whether consolidation of the new Spanish words would increase their interference strength. We found significant main effects of interference in naming latencies and accuracy: Participants speeded up less and were less accurate to recall words in English for which they had learned Spanish translations, compared with words for which they had not. Consolidation time did not significantly affect these interference effects. Thus, learning a new language indeed comes at the cost of subsequent retrieval ability in other FLs. Such interference effects set in immediately after learning and do not need time to emerge, even when the other FL has been known for a long time.

The pretesting effect thrives in the presence of competing information

Taking a pretest (e.g., blanket - ?) before some target material (blanket - sheet) is studied can promote recall of that material on a subsequent final test compared to material which was initially only studied. Here, we examine whether such pretesting can shield the tested material from interference-induced forgetting, which often occurs when before final testing, related material is encountered. We applied a typical pretesting task but asked subjects, between acquisition and final testing of the target list (list 1), to study two additional lists of items with either completely new and unique pairs (e.g., atom - cell) or overlapping - and thus potentially interfering - pairs (e.g., blanket - sleep). Target-list recall on the final test showed a typical pretesting effect for unique pairs, but the size of the effect even increased for overlapping pairs, as recall of study-only pairs was impaired, whereas recall of pretest pairs was left largely unaffected. This held regardless of whether a low (Experiment 1) or high (Experiment 2) degree of learning was induced for the interfering material, suggesting that pretesting can indeed protect the tested material from interference. These findings indicate that pretesting could play a significant role in educational settings where information often needs to be retained in the presence of competing information.

Genetic dissection of mutual interference between two consecutive learning tasks in Drosophila

Animals can continuously learn different tasks to adapt to changing environments and, therefore, have strategies to effectively cope with inter-task interference, including both proactive interference (Pro-I) and retroactive interference (Retro-I). Many biological mechanisms are known to contribute to learning, memory, and forgetting for a single task, however, mechanisms involved only when learning sequential different tasks are relatively poorly understood. Here, we dissect the respective molecular mechanisms of Pro-I and Retro-I between two consecutive associative learning tasks in Drosophila. Pro-I is more sensitive to an inter-task interval (ITI) than Retro-I. They occur together at short ITI (<20 min), while only Retro-I remains significant at ITI beyond 20 min. Acutely overexpressing Corkscrew (CSW), an evolutionarily conserved protein tyrosine phosphatase SHP2, in mushroom body (MB) neurons reduces Pro-I, whereas acute knockdown of CSW exacerbates Pro-I. Such function of CSW is further found to rely on the γ subset of MB neurons and the downstream Raf/MAPK pathway. In contrast, manipulating CSW does not affect Retro-I as well as a single learning task. Interestingly, manipulation of Rac1, a molecule that regulates Retro-I, does not affect Pro-I. Thus, our findings suggest that learning different tasks consecutively triggers distinct molecular mechanisms to tune proactive and retroactive interference.

Differential effects of proactive and retroactive interference in value-directed remembering for younger and older adults

We are often presented with more information than we can remember, and we must selectively focus on the most valuable information to maximize memory utility. Most tests of value-based memory involve encoding and then being tested on a list of recently studied information. Thus, people are focused on memory for the current list and are encouraged to forget information from earlier lists. However, prior learning can influence later memory, in both interfering and beneficial ways, and there may be age-related differences in how younger and older adults are influenced by the costs and benefits of prior learning and interference. In the present study, we presented younger and older adults with words paired with point values to remember for a later test but rather than asking participants to only recall words from the just-studied list, participants were asked to recall all studied words on each recall test. Results revealed that younger adults were more likely to recall words from previous lists than older adults, indicating that older adults were more susceptible to retroactive interference. Moreover, although selectivity is often preserved in older adults when study-test cycles are independent, a buildup of proactive interference arising from previously studied words reduced memory selectivity in older adults. Thus, when presented with more information than one can remember, younger adults are better at combating interference and recalling valuable information, while older adults may engage in selective forgetting of prior lists to enhance a "present-focused" form of memory, possibly as a result of impaired inhibitory control. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Semantic relatedness retroactively boosts memory and promotes memory interdependence across episodes

Two fundamental issues in memory research concern when later experiences strengthen or weaken initial memories and when the two memories become linked or remain independent. A promising candidate for explaining these issues is semantic relatedness. Here, across five paired-associate learning experiments (N=1000), we systematically varied the semantic relatedness between initial and later cues, initial and later targets, or both. We found that learning retroactively benefited long-term memory performance for semantically related words (vs. unshown control words), and these benefits increased as a function of relatedness. Critically, memory dependence between initial and later pairs also increased with relatedness, suggesting that pre-existing semantic relationships promote interdependence for memories formed across episodes. We also found that modest retroactive benefits, but not interdependencies, emerged when subjects learned via studying rather than practice testing. These findings demonstrate that semantic relatedness during new learning retroactively strengthens old associations while scaffolding new ones into well-fortified memory traces.

Associating the old with the new

New memories can strengthen old memories if the recent and past experience contain elements that are semantically related.

Blocking is not 'pure' cue competition: Renewal-like effects in forward and backward blocking indicate contributions by associative cue interference

Blocking (i.e., reduced responding to cue X following YX-outcome pairings in Phase 2 as a consequence of cue Y having been paired with the outcome in Phase 1) is one of the signature phenomena in Pavlovian conditioning. Its discovery promoted the development of multiple associative models, most of which viewed blocking as an instance of pure cue competition (i.e., a decrease in responding attributable to training two conditioned stimuli in compound). Two experiments are reported in which rats were examined in a fear conditioning paradigm (i.e., lick suppression), and context dependency of retrieval at test was used as an index of associative cue interference (i.e., a decrease in responding to a target cue as a result of training a second cue with the same outcome but without concurrent presentation of the two cues). Specifically, we observed renewal of forward-blocking which parallels renewal of proactive interference, and renewal of backward-blocking which parallels renewal of retroactive interference. Thus, both backward-blocking (Experiment 1, embedded in a sensory preconditioning design) and forward-blocking (Experiment 2, conducted in first-order conditioning) appear to be influenced by retroactive and proactive interference, respectively, as well as cue competition. Consequently, blocking, long regarded as a benchmark example of pure cue competition, is sometimes a hybrid of cue competition and associative interference. Finally, the Discussion considers whether stimulus competition and associative interference are two independent phenomena or products of a single underlying process. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A reappraisal of acute doses of benzodiazepines as a model of anterograde amnesia

OBJECTIVE

Acute administration of benzodiazepines is considered a pharmacological model of general organic anterograde amnesias (OAA). We sought to determine which type of amnesia these drugs best model by comparing the effects of diazepam with those reported in amnesiacs regarding working memory capacity (WMC), susceptibility to retroactive interference (RI), and accelerated forgetting.

METHODS

In this double-blind, parallel-group design study, 30 undergraduates were randomly allocated to acute oral treatments with 15 mg diazepam or placebo. WMC and story recall were assessed pre- and post-treatment. Story presentation was succeeded by 10 min of RI (spotting differences in pictures) or minimal RI (doing nothing in a darkened room). Delayed story recall was assessed under diazepam and 7 days later in a drug-free session to assess accelerated forgetting.

RESULTS

Recall of stories encoded under diazepam, whether reactivated or not, was severely impaired (anterograde amnesia). However, diazepam did not impair WMC, increase susceptibility to RI, or accelerate forgetting.

CONCLUSIONS

Diazepam's amnestic effects mirror those in patients with probable severe medial temporal damage, mostly restricted to initial consolidation and differ from other OAA (Korsakoff syndrome, frontal, transient epileptic, posttraumatic amnesia, and most progressive amnesias) in terms of WMC, susceptibility to RI and accelerated forgetting.

Memory Susceptibility to Retroactive Interference Is Developmentally Regulated by NMDA Receptors

Retroactive interference (RI) occurs when new incoming information impairs an existing memory, which is one of the primary sources of forgetting. Although long-term potentiation (LTP) reversal shows promise as the underlying neural correlate, the key molecules that control the sensitivity of memory circuits to RI are unknown, and the developmental trajectory of RI effects is unclear. Here we found that depotentiation in the hippocampal dentate gyrus (DG) depends on GluN2A-containing NMDA receptors (NMDARs). The susceptibility of LTP to disruption progressively increases with the rise in the GluN2A/GluN2B ratio during development. The vulnerability of hippocampus-dependent memory to interference from post-learning novelty exploration is subject to similar developmental regulation by NMDARs. Both GluN2A overexpression and GluN2B downregulation in the DG promote RI-induced forgetting. Altogether, our results suggest that a switch in GluN2 subunit predominance may confer age-related differences to depotentiation and underlie the developmental decline in memory resistance to RI.

Does retrieving a memory insulate it against memory inhibition? A retroactive interference study

Several recent studies suggest that an initial retrieval attempt imbues retrieved memories with special resilience against future interference and other forgetting mechanisms. Here we report two experiments examining whether memories established through initial retrieval remain subject to retrieval-induced forgetting. Using a version of a classical retroactive interference design, we trained participants on a list of A-B pairs via anticipation - constituting a form of retrieval practice. After next training participants on interfering A-C pairs, they performed 0-12 additional A-C anticipation trials. Because these trials required retrieval of A-C pairs, they should function similarly to retrieval practice in paradigms establishing retrieval-induced forgetting. We observed robust evidence that retroactive interference generalises to final memory tests involving novel, independent memory probes. Moreover, in contrast to practising retrieval of A-C items, their extra study failed to induce cue-independent forgetting of the original B items. Together, these findings substantiate the role of retrieval-related inhibitory processes in a traditional retroactive interference design. Importantly, they indicate that an initial retrieval attempt on a competitor does not abolish retrieval-induced forgetting, at least not in the context of this classic design. Although such an attempt may protect against inhibition in some circumstances, the nature of those circumstances remains to be understood.

Different reactivation procedures enable or prevent episodic memory updating

The present study asked whether the specific method of reactivation modulates the impact of new learning on reactivated episodic memories. The study consisted of three sessions that were spaced 48 hr apart. It used an ABAC paradigm that allowed for the simultaneous assessment of retroactive interference (RI: reduced A-B recall after A-C learning) and intrusions from C into A-B recall. In Session 1, participants learned a list of paired-associates A-B. In Session 2, memory for A-B was reactivated or not and then participants either learned a second list of paired-associates A-C or completed a control task. Three different reminder conditions were compared to a no-reminder condition: a test condition, in which participants were asked to recall B in response to A, a restudy condition, in which A-B pairs were presented again for study, and a cue-word only reminder condition, in which A cues were presented in an unrelated rating task. In Session 3, recall of A-B was tested. Moderate or indirect reactivation of A-B (presentation of cue-words only) resulted in high RI effects and intrusion rates, whereas strong and direct reactivation (test and restudy) drastically reduced these effects. We suggest that direct reactivation of A-B before A-C learning strengthens memory and draws attention to list differences, thereby enhancing list segregation, and reducing memory updating.

Differential Effects of Novel Dopamine Reuptake Inhibitors on Interference With Long-Term Social Memory in Mice

In the laboratory, long-term social recognition memory (SRM) in mice is highly susceptible to proactive and retroactive interference. Here, we investigate the ability of novel designed dopamine (DA) re-uptake inhibitors (rac-CE-123 and S-CE-123) to block retroactive and proactive interference, respectively. Our data show that administration of rac-CE-123 30 min before learning blocks retroactive interference that has been experimentally induced at 3 h, but not at 6 h, post-learning. In contrast, S-CE-123 treatment 30 min before learning blocked the induction of retroactive interference at 6 h, but not 3 h, post-learning. Administration of S-CE-123 failed to interfere with proactive interference at both 3 h and 6 h. Analysis of additional behavioral parameters collected during the memory task implies that the effects of the new DA re-uptake inhibitors on retroactive and proactive interference cannot easily be explained by non-specific effects on the animals’ general social behavior. Furthermore, we assessed the mechanisms of action of drugs using intracerebral in vivo-microdialysis technique. The results revealed that administration of rac-CE-123 and S-CE-123 dose-dependently increased DA release within the nucleus accumbens of freely behaving mice. Thus, the data from the present study suggests that the DA re-uptake inhibitors tested protect the consolidation of long-term social memory against interference for defined durations after learning. In addition, the data implies that DA signaling in distinct brain areas including the nucleus accumbens is involved in the consolidation of SRM in laboratory mice.

Successful list-method directed forgetting without retroactive interference of post-instruction learning

The focus of the study is the role of interference in list-method directed forgetting. More specifically, our question was whether retroactive interference of the to-be-remembered information is a necessary prerequisite for the directed forgetting effect. In Experiment 1 we used a directed forgetting procedure with one learning list without the interference of any to-be-remembered information. In line with previous results, we did not find a significant directed forgetting effect. Experiment 2 applied a directed forgetting procedure with two study lists, however, the forget instruction was given following the second list. So, List 2 items were designated as to-be-forgotten items, without further learning, whereas List 1 items were to-be-remembered items. The forget instruction selectively decreased the recall of List 2 items, without decreasing the recall performance for List 1. In Experiment 3, using the same procedure with different items, smaller learning lists and reversed output order, we replicated the results of Experiment 2. Altogether, these results point to a flexible, goal-related nature of the directed forgetting phenomenon, showing that some form of interference is a necessary requirement for successful directed forgetting. However, proactive interference of to-be-remembered information in interaction with a forget instruction is suitable for forgetting of subsequently encoded information.

When Learning Disturbs Memory - Temporal Profile of Retroactive Interference of Learning on Memory Formation

Introduction: Consolidation is defined as the time necessary for memory stabilization after learning. In the present study we focused on effects of interference during the first 12 consolidation minutes after learning. Participants had to learn a set of German - Japanese word pairs in an initial learning task and a different set of German - Japanese word pairs in a subsequent interference task. The interference task started in different experimental conditions at different time points (0, 3, 6, and 9 min) after the learning task and was followed by subsequent cued recall tests. In a control experiment the interference periods were replaced by rest periods without any interference. Results: The interference task decreased memory performance by up to 20%, with negative effects at all interference time points and large variability between participants concerning both the time point and the size of maximal interference. Further, fast learners seem to be more affected by interference than slow learners. Discussion: Our results indicate that the first 12 min after learning are highly important for memory consolidation, without a general pattern concerning the precise time point of maximal interference across individuals. This finding raises doubts about the generalized learning recipes and calls for individuality of learning schedules.

Nonspecific Retroactive Interference in Children and Adults

Retroactive interference (RI) is a primary source of forgetting and occurs when new information disrupts or damages an existing memory. Prior research has shown that children are susceptible to RI when the to-be-remembered and interfering information are similar, but it is unclear whether they are also vulnerable to nonspecific RI . This form of interference occurs when a memory is disrupted by an unrelated and dissimilar distractor task, and the present study explored six- and seven-year-olds susceptibility to such nonspecific RI. In two experiments, participants learnt a list of words and completed a free recall test 5 min later. During the interval, participants either remained quiet (the control condition) or completed spot-the-difference puzzles (the interference condition). In Experiment 1, the children were highly susceptible to nonspecific interference, whereas a sample of adults were not affected by the interfering task. However, when a new sample of children were given more time to encode and retrieve the words in Experiment 2, they were able to resist interference. Nonspecific RI can damage children's memory, but they do have the ability to prevent this form of interference in certain circumstances.

Non-Interfering Effects of Active Post-Encoding Tasks on Episodic Memory Consolidation in Humans

So far, studies that investigated interference effects of post-learning processes on episodic memory consolidation in humans have used tasks involving only complex and meaningful information. Such tasks require reallocation of general or encoding-specific resources away from consolidation-relevant activities. The possibility that interference can be elicited using a task that heavily taxes our limited brain resources, but has low semantic and hippocampal related long-term memory processing demands, has never been tested. We address this question by investigating whether consolidation could persist in parallel with an active, encoding-irrelevant, minimally semantic task, regardless of its high resource demands for cognitive processing. We distinguish the impact of such a task on consolidation based on whether it engages resources that are: (1) general/executive, or (2) specific/overlapping with the encoding modality. Our experiments compared subsequent memory performance across two post-encoding consolidation periods: quiet wakeful rest and a cognitively demanding n-Back task. Across six different experiments (total N = 176), we carefully manipulated the design of the n-Back task to target general or specific resources engaged in the ongoing consolidation process. In contrast to previous studies that employed interference tasks involving conceptual stimuli and complex processing demands, we did not find any differences between n-Back and rest conditions on memory performance at delayed test, using both recall and recognition tests. Our results indicate that: (1) quiet, wakeful rest is not a necessary prerequisite for episodic memory consolidation; and (2) post-encoding cognitive engagement does not interfere with memory consolidation when task-performance has minimal semantic and hippocampally-based episodic memory processing demands. We discuss our findings with reference to resource and reactivation-led interference theories.

Material-specific retroactive interference effects of the Wechsler Adult Intelligence Scale-Fourth Edition on the Wechsler Memory Scale-Fourth Edition in a nonclinical sample

INTRODUCTION

This study investigated proactive and retroactive interference effects between the Wechsler Memory Scale-Fourth Edition (WMS-IV) using the flexible approach, and the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV).

METHOD

One hundred and eighty nonclinical participants were assigned to a four (visual interference, verbal interference, visual and verbal interference, vs. no interference) by two (retroactive vs. proactive) between-subjects design. The administration order of the tests was counterbalanced (i.e., administration of the WAIS-IV prior to the WMS-IV, and the WAIS-IV administered during the delay interval of the WMS-IV).

RESULTS

The WAIS-IV produced significant retroactive interference effects on the WMS-IV; however, no proactive interference effect was observed. The retroactive interference effect was dependent on material specificity.

CONCLUSIONS

The results indicate that material presented within the delay of the WMS-IV can have a significant effect on subsequent delayed recall. Clinicians should carefully consider the effects associated with carry-over effects of these tests when using them in combination.

Sequential dynamics in visual short-term memory

Visual short-term memory (VSTM) is thought to help bridge across changes in visual input, and yet many studies of VSTM employ static displays. Here we investigate how VSTM copes with sequential input. In particular, we characterize the temporal dynamics of several different components of VSTM performance, including: storage probability, precision, variability in precision, guessing, and swapping. We used a variant of the continuous-report VSTM task developed for static displays, quantifying the contribution of each component with statistical likelihood estimation, as a function of serial position and set size. In Experiments 1 and 2, storage probability did not vary by serial position for small set sizes, but showed a small primacy effect and a robust recency effect for larger set sizes; precision did not vary by serial position or set size. In Experiment 3, the recency effect was shown to reflect an increased likelihood of swapping out items from earlier serial positions and swapping in later items, rather than an increased rate of guessing for earlier items. Indeed, a model that incorporated responding to non-targets provided a better fit to these data than alternative models that did not allow for swapping or that tried to account for variable precision. These findings suggest that VSTM is updated in a first-in-first-out manner, and they bring VSTM research into closer alignment with classical working memory research that focuses on sequential behavior and interference effects.

Rapid eye movement and non-rapid eye movement sleep contributions in memory consolidation and resistance to retroactive interference for verbal material

STUDY OBJECTIVES

To test the hypothesis that rapid eye movement (REM) sleep contributes to the consolidation of new memories, whereas non-rapid eye movement (NREM) sleep contributes to the prevention of retroactive interference.

DESIGN

Randomized, crossover study.

SETTING

Two sessions of either a morning nap or wakefulness.

PARTICIPANTS

Twenty-five healthy young adults.

INTERVENTIONS

Declarative learning of word pairs followed by a nap or a wake interval, then learning of interfering word pairs and delayed recall of list A.

MEASUREMENTS AND RESULTS

After a restricted night (24:00-06:00), participants learned a list of word pairs (list A). They were then required to either take a nap or stay awake during 45 min, after which they learned a second list of word pairs (list B) and then had to recall list A. Fifty percent of word pairs in list B shared the first word with list A, resulting in interference. Ten subjects exhibited REM sleep whereas 13 subjects exhibited NREM stage 3 (N3) sleep. An interference effect was observed in the nap but not in the wake condition. In post-learning naps, N3 sleep was associated with a reduced interference effect, which was not the case for REM sleep. Moreover, participants exhibiting N3 sleep in the post-learning nap condition also showed a reduced interference effect in the wake condition, suggesting a higher protection ability against interference.

CONCLUSION

Our results partly support the hypothesis that non-rapid eye movement sleep contributes in protecting novel memories against interference. However, rapid eye movement sleep-related consolidation is not evidenced.

Reversing the course of forgetting

Forgetting functions were generated for pigeons in a delayed matching-to-sample task, in which accuracy decreased with increasing retention-interval duration. In baseline training with dark retention intervals, accuracy was high overall. Illumination of the experimental chamber by a houselight during the retention interval impaired performance accuracy by increasing the rate of forgetting. In novel conditions, the houselight was lit at the beginning of a retention interval and then turned off partway through the retention interval. Accuracy was low at the beginning of the retention interval and then increased later in the interval. Thus the course of forgetting was reversed. Such a dissociation of forgetting from the passage of time is consistent with an interference account in which attention or stimulus control switches between the remembering task and extraneous events.

A natural genetic polymorphism affects retroactive interference in Drosophila melanogaster

As environments change, animals update their internal representations of the external world. New information about the environment is learned and retained whereas outdated information is disregarded or forgotten. Retroactive interference (RI) occurs when the retrieval of previously learned information is less available owing to the acquisition of recently acquired information. Even though RI is thought to be a major cause of forgetting, its functional significance is still under debate. We find that natural allelic variants of the Drosophila melanogaster foraging gene known to affect rover and sitter behaviour differ in RI. More specifically, rovers who were previously shown to experience greater environmental heterogeneity while foraging display RI whereas sitters do not. Rover responses are biased towards more recent learning events. These results provide an ecological context to investigate the function of forgetting via RI and a suitable genetic model organism to address the evolutionary relevance of cognitive tasks.

Profound retroactive interference in anterograde amnesia: What interferes?

OBJECTIVE

Anterograde amnesia is characterized by a profound inability to retain new information. Recent research suggests that at least some of this severe memory impairment may be the product of retroactive interference. What exactly interferes with memory in amnesic patients, however, remains unknown. The aim of the present study was to examine whether or not postlearning material which is highly dissimilar from the material to be remembered would interfere with amnesic patients' memory.

METHOD

Prose retention was tested in 10 densely amnesic patients and 10 controls following a 10 minute delay period, which was either unfilled (minimal interference) or filled with a tone detection task in which participants were required to listen for piano notes (nonspecific interference).

RESULTS

A significant nonspecific retroactive interference effect was observed in the amnesic patients (p < 0.004): Whereas 7 out of the 10 amnesic patients were able to recall some prose material following the unfilled delay period, only 1 of them was able to recall any material after the tone detection delay.

CONCLUSIONS

The data reveal that some amnesic patients have the capacity to retain new material for much longer than usual but that apparently any new postlearning information profoundly interferes with such retention. This nonspecific retroactive interference effect deviates from the item-specific interference effect that is typically assessed in clinical practice and which is frequently observed in patients with executive impairment. We hypothesize that these interference effects are qualitatively different, occurring during distinct memory processes, namely retrieval (item-specific interference) and consolidation (nonspecific interference).

Forgetting due to retroactive interference: a fusion of Müller and Pilzecker's (1900) early insights into everyday forgetting and recent research on anterograde amnesia

Ebbinghaus' seminal work suggested that forgetting occurred as a function of time. However, it raised a number of fundamental theoretical issues that still have not been resolved in the literature. Müller and Pilzecker (1900) addressed some of these issues in a remarkable manner but their observations have been mostly ignored in recent years. Müller and Pilzecker (1900) showed that the materials and the task that intervene between presentation and recall may interfere with the to-be-remembered items, and they named this phenomenon "retroactive interference" (RI). They further asked whether there is a type of RI that is based only on distraction, and not on the similarity between the memoranda and the interfering stimuli. Their findings, and our follow up research in healthy volunteers and amnesiacs, confirm that forgetting can be induced by any subsequent mentally effortful interpolated task, irrespective of its content; the interpolated "interfering" material does not have to be similar to the to-be-remembered stimuli.