Human memory reconsolidation can be explained using the temporal context model

Recent work by Hupbach, Gomez, Hardt, and Nadel (Learning & Memory, 14, 47–53, 2007) and Hupbach, Gomez, and Nadel (Memory, 17, 502–510, 2009) suggests that episodic memory for a previously studied list can be updated to include new items, if participants are reminded of the earlier list just prior to learning a new list. The key finding from the Hupbach studies was an asymmetric pattern of intrusions, whereby participants intruded numerous items from the second list when trying to recall the first list, but not viceversa. Hupbach et al. (2007; 2009) explained this pattern in terms of a cellular reconsolidation process, whereby first-list memory is rendered labile by the reminder and the labile memory is then updated to include items from the second list. Here, we show that the temporal context model of memory, which lacks a cellular reconsolidation process, can account for the asymmetric intrusion effect, using well-established principles of contextual reinstatement and item–context binding.     

A positional coding mechanism in pigeons after learning multiple three-item lists

Pigeons were trained on three three-item lists (List 1: A₁ → B₁ → C_1; List 2: A₂ → B₂ → C_2; List 3: A₃ → B₃ → C₃). After sessions in which any one of the three lists could be presented on a trial, derived-maintained list and derived-changed list probe trials were introduced. The derived list probe trials were composed of three items, one drawn from each of the training lists. On derived-maintained probe trials, each item was in the same ordinal position it occupied during training (e.g., A₃ → B₁ → C₂). On derived-changed probe trials, items that occupied the second and third position during training were exchanged (e.g., A₂ → C₃ → B₁). The performance of subjects on derived-maintained probe trials was significantly above chance and no different to that observed on the training lists. In contrast, subjects’ performance on derived-changed probe trials was significantly below chance. To our knowledge, this is the first study that has demonstrated pigeons are able to learn and retain multiple three-item lists. In addition, subjects’ performance on the derived-maintained probe trials suggests that they acquire knowledge of each list item’s ordinal position when learning multiple lists.     

Rate and frequency as determinants of learning with complete and discrete list presentation

In Experiment 1, complete presentation of the study list produced better free recall learning than did the usual item-by-item (discrete) presentation. The difference was large and held for items occurring one, two, or three times within a list, whether items were spaced or massed, and for discrete presentation rates of 2, 4, and 6 sec/item. Experiment 2 replicated this superiority of complete over discrete presentation (equating total study time), and Experiment 3 extended the finding to paired associate learning. Experiments 2 and 3 indicated that multiple presentations of a list at fast rates were superior to a single presentation at a more standard rate and only slightly inferior to a single, complete presentation. Practical implications for instruction were pointed out, as were problems that certain of the results pose for theories that emphasize strategic (or at least extended) processing of items for encoding.     

The role of overt language production in the Hebb repetition effect

The Hebb repetition effect (Hebb, 1961) occurs when recall performance improves for a list that is repeated during a serial-recall task. This effect is considered a good experimental analogue to language learning. Our objective was to evaluate the role of overt language production in language learning by manipulating recall direction during a Hebb repetition paradigm. In each trial, seven nonsense syllables were presented auditorily. Participants had to orally recall the items either in the presentation order or in reverse order. One sequence was repeated every third trial. In Experiment 1, we compared learning from a group that had recalled the items in their presentation order to learning from a group that had recalled the items in the reverse order. The two groups yielded similar learning rates. In Experiment 2, recall direction was varied between trials. The learning rate was not affected when recall direction varied between trials, suggesting a limited role of overt language production in language learning.     

Overt language production plays a key role in the Hebb repetition effect

When asked to recall verbatim a short list of items, performance is very limited. However, if the list of items is repeated across trials, recall performance improves. This phenomenon, known as the Hebb repetition effect (Hebb, 1961; Brain Mechanisms and Learning: A Symposium, pp. 37–51), is considered a laboratory analogue of language learning. In effect, learning a new word implies the maintenance of a series of smaller units, such as phonemes or syllables, in the correct order for a short amount of time before producing them. The sequence of smaller units is typically presented more than once. In the present study, we investigated the role of overt language production in language learning by manipulating recall direction. If the learning of a repeated list of items relies on overt language production processes, changing list production order by manipulating recall direction should impact the learning of the list. In Experiment 1, one list was repeated every third trial, and recall direction of the repeated list changed on the ninth repetition. In Experiment 1a, the repeated list changed from a forward to a backward order recall, where participants had to recall the items in reverse presentation order. In Experiment 1b, the repeated list changed from a backward to a forward order recall. Results showed a cost in recall performance for the repeated list when recall direction switched from forward to backward recall, whereas it was unaffected by the change from backward to forward recall. In Experiment 2, we increased the number of trials before introducing the change from a backward to a forward order recall. Results showed a decrement in recall performance for the repeated list following the change in recall direction, suggesting that language production processes play a role in the Hebb repetition effect.     

Retroactive inhibition as a function of similarity of meaning in free-recall learning

Summary Retroactive inhibition in free-recall learning was measured under six degrees of meaningful similarity: zero, low, low-medium, medium, medium-high, and high. For each degree of similarity, an experimental and a control group of 20 Ss each learned a list of 20 unrelated adjectives through three cycles of alternate study and unpaced free recall. Immediately thereafter, the experimental group learned a second list of 20 adjectives, while the control group rested. Finally, a single recall trial was administered to both groups to measure first-list retention. The results have revealed a relationship which is at variance with the relationships observed in both serial and paired-associate learning but conforms to the curvilinear function earlier formulated by Skaggs and Robinson. Fresh arguments are offered in defence of the Skaggs-Robinson hypothesis.     

DRM paradigm for people's name lures and effects of delaying conscious thought of the lure at encoding

The experiment was conducted to test whether or not presentation order is an important factor to explain why Critical Lures of people's names are falsely recalled relatively rarely in the Deese-Roediger-McDermott paradigm. For half of the participants, the most highly associated items were presented at the start of the list (Standard condition). For the other half, presentation of the most strongly associated items was delayed until the middle of the list (Delayed condition). This manipulation had no significant effect on the probability of falsely recalled Critical Lures or on that of veridical recall of list items, but in the Delayed condition the mean number of intrusions other than the Critical Lures was higher than that in the Standard condition.     

Developmental differences in frequency judgments of words and pictures

Children in kindergarten, third, and fifth grades were presented a list of either pictures or words (with items presented for varying numbers of times on the study trial). In both picture and word conditions, half of the Ss estimated how many times each item had been presented (absolute judgments) and the other half judged which of two items had occurred more often on the study trial (relative judgments). The primary finding was that while frequency judgment performance improved with age for both pictures and words, there was relatively greater improvement for pictures (i.e., the picture-word difference increased with age). These results lend strong support to the frequency theory of discrimination learning and, in particular, may be useful in accounting for effects associated with age and with age by stimulus mode interactions.     

Item method directed forgetting diminishes false memory

Directed forgetting may reduce the ORM false memory illusion by interfering with meaning processing. Participants were presented with a list composed of six 10-word semantically associated sub-lists, and they were either (a) asked to remember a ll list it ems or (b) asked to remember all associates from sub-lists and to forget all associates from other sub-lists. All participants were requested to recall and recognise list items. Although directed forgetting effects have been previously reported only for true responses in the ORM paradigm with the list method, we also found directed forgetting for false responses with the item method. Such forgetting instructions reduced both verbatim and meaning processing, decreasing both the intrusion and the false alarm rate. These results are consistent with two-process explanations of DRM false memories, such as fuzzy-trace theory, and add to our understanding of false memory editing.     

The influence of agenda-based and habitual processes on item selection during study

Research on study-time allocation has largely focused on agenda-based regulation, such as whether learners select items for study that are in their region of proximal learning. In 4 experiments, the authors evaluated the contribution of habitual responding to study-time allocation (e.g., reading from left to right). In Experiments 1 and 2, participants selected items for study from a 3-item array. In Experiment 1, pairs were ordered by learning ease from left to right or in the reverse order. In Experiment 2, pairs were in a column with the easiest item either in the top or bottom position. Participants more likely chose to study the easiest item first when it was presented in the prominent position of an array, but when the difficult item was in the prominent position, it was more often chosen first for study. In Experiment 3, a 3 × 3 array was used. In 1 group, the 3 easy items were in the left column and the 3 difficult ones were in the right column; in another group, these columns were reversed. Participants largely chose items in a top-down or left-to-right order. In Experiment 4, items were presented sequentially for item selection, with either the difficult items presented first (followed by progressively easier items) or in the reverse order. Participants could choose half the items for restudy, and they were more likely to choose items presented earlier in the list, regardless of presentation order. These and other outcomes indicate that both agenda-based regulation (in terms of using the region of proximal learning) and habitual responding contribute to people's selection of items for study.     

Spontaneous categorizers retain more than spontaneous alphabetizers

Immediate and delayed free recall of unstructured verbal materials were assessed for alphabetizers and categorizers after varying study times. Alphabetizers and categorizers did not differ in immediate recall, but retention following a 6-day interval was consistently higher for categorizers than for alphabetizers. Both immediate and delayed recall increased with study time, which did not interact with learning strategy. In the next experiment alphabetizers and categorizers learned two lists, the second of which was categorically structured or unstructured. No retroactive interference on first-list recall was produced by the learning of the structured list, but the learning of the unstructured list produced retroactive interference for the alphabetizers only. It was suggested that, although both alphabetizers and categorizers probably use their respective strategies for other verbal tasks, the categoric strategy should create less interference because specific 'categories are rarely encountered in successive tasks.     

Output buffer storage and the modality of recall

In two experiments, subjects were presented with two lists of visual items simultaneously, both of which were to be recalled. The order of recall of the lists was manipulated. In Experiment 1, subjects were required to recall one list by speaking it and the other by writing it down. Prior knowledge of the particular mode of output required for each list resulted in significantly higher levels of recall than in a condition in which the output mode for each list was not known until after presentation. This result suggests that there may be at least two modality-specific output buffers. Experiment 2 employed the same method of presentation, but spoken recall of both lists was required. In addition, the priority of the lists was manipulated, and articulatory suppression was required in half of the trials. There was an effect of priority and of recall order, together with an interaction between the two. In contrast to the results of FitzGerald and Broadbent (1985a), however, who carried out a similar experiment but with written recall, articulatory suppression significantly reduced the priority and recall order interaction. It is concluded that there is one form of output buffer storage for written or manual output and one for spoken output.     

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.     

Modification and Origin of Certain Beliefs in Superstition Among 96 College Students

An experiment was designed to study the effect of practice on anagram solving. This was accomplished through the presentation of three anagram lists to 243 subjects and a comparison made of first-list performance (early stage of practice) with last-list performance (later stage of practice). The results revealed the presence of a significantly greater number of solutions on the last, rather than the first list, clearly indicating the presence of a general practice effect in the solution of anagrams. The failure of earlier studies to demonstrate this phenomenon was attributed to the use of relatively short anagram lists in previous research.     

Directed forgetting in the list method affects recognition memory for source

The effects of list-method directed forgetting on recognition memory were explored. In Experiment 1 (N = 40), observers were instructed to remember words and their type-cases; in Experiment 2 (N = 80), the instruction was to remember words and their colours. Two lists of 10 words were presented; after the first list, half of the observers (forget) were instructed to forget that list, and the other half (remember) were not given the forget instruction. Recognition of items (words) as well as source (encoding list + case/colour) was measured for forget and remember observers. The forget instruction affected case/colour memory more consistently than item and list memory; a multinomial analysis indicated that source information was affected by the forget instructions. The results indicated that recognition of source information may be a more sensitive indicator of forgetting than recognition of items.     

Working memory capacity predicts the beneficial effect of selective memory retrieval

Selective retrieval of some studied items can both impair and improve recall of the other items. This study examined the role of working memory capacity (WMC) for the two effects of memory retrieval. Participants studied an item list consisting of predefined target and nontarget items. After study of the list, half of the participants performed an imagination task supposed to induce a change in mental context, whereas the other half performed a counting task which does not induce such context change. Following presentation of a second list, memory for the original list's target items was tested, either with or without preceding retrieval of the list's nontarget items. Consistent with previous work, preceding nontarget retrieval impaired target recall in the absence of the context change, but improved target recall in its presence. In particular, there was a positive relationship between WMC and the beneficial, but not the detrimental effect of memory retrieval. On the basis of the view that the beneficial effect of memory retrieval reflects context-reactivation processes, the results indicate that individuals with higher WMC are better able to capitalise on retrieval-induced context reactivation than individuals with lower WMC.     

List-method directed forgetting: The forget cue improves both encoding and retrieval of postcue information

In list-method directed forgetting, people are cued to forget a previously studied item list and to learn a new list instead. Such cuing typically leads to forgetting of the first list and to memory enhancement of the second, referred to as list 1 forgetting and list 2 enhancement. In the present study, two experiments are reported that examined influences of items' serial learning position in a list and the two lists' output order on list-method directed forgetting. The results show that list output order influences list 2 enhancement but not list 1 forgetting. The enhancement was higher when list 2 was recalled first than when list 1 was recalled first and, in both cases, was higher for early list 2 items than for middle and late list 2 items. In contrast, the forgetting was equally present for all list 1 items and did not depend on the two lists' output order. The findings suggest that two separate factors can contribute to list 2 enhancement: one (encoding) factor that is restricted to early list 2 items and does not depend on list output order, and another (retrieval) factor that pertains to all list 2 items and varies with the two lists' output order. A new two-mechanism account of directed forgetting is suggested that reconciles previous (encoding or retrieval) views on list 2 enhancement.     

Testing effects in mixed- versus pure-list designs

In the present study, we investigated the role of list composition in the testing effect. Across three experiments, participants learned items through study and initial testing or study and restudy. List composition was manipulated, such that tested and restudied items appeared either intermixed in the same lists (mixed lists) or in separate lists (pure lists). In Experiment 1, half of the participants received mixed lists and half received pure lists. In Experiment 2, all participants were given both mixed and pure lists. Experiment 3 followed Erlebacher’s (Psychological Bulletin, 84, 212–219, 1977) method, such that mixed lists, pure tested lists, and pure restudied lists were given to independent groups. Across all three experiments, the final recall results revealed significant testing effects for both mixed and pure lists, with no reliable difference in the magnitude of the testing advantage across list designs. This finding suggests that the testing effect is not subject to a key boundary condition—list design—that impacts other memory phenomena, including the generation effect.     

Coding strategies,perceptual grouping,and the “variability effect” in free recall

Three experiments examined the effects of constant vs. varied input of letter strings on recall, and then examined the effects of such training in the learning of new lists of letter strings. Letter strings were constructed from pairs of trigrams spatially grouped, and were presented either consistently or with different spatial groupings on successive presentations. In Experiments I and II, varied input produced substantially greater recall than constant input. When transferred to a new list of letter strings, containing either the same general structure or a new scrambled structure, recall of the second list was determined primarily by conditions of first-list input, and unaffected by second-list structure. Although the "variability effect" did not appear in the training phase of Experiment III, Varied input led subjects to regroup or integrate the letter sequences more frequently and produced similar transfer effects as in Experiments I and II.     

The within-list distributed practice effect: Tests of the varied context and varied encoding hypotheses

The present studies provided separate tests of the varied context and varied encoding hypotheses of the MP-DP effect. The investigation of varied encoding used an incidental learning procedure in which the nature of the orienting task was manipulated such that the subject attended to different attributes of words (varied encoding) or only one attribute (same encoding). While the prediction that the recall of MP-DP items should be comparable under comparable levels of encoding was not supported, differences were obtained in recall of items under same and variable orienting task conditions. An MP-DP effect was obtained under the incidental learning procedure. Tests of varied context involved the presentation of target items in list contexts which were the same or different from list contexts on previous occurrences of the item. The prediction that recall of items surrounded by different context should exceed that of items surrounded by the same context was not supported.