The retrieval hypothesis as an explanation of induced retrograde amnesia

The present experiment tested the hypothesis that retrograde induced amnesia is due to retrieval failure and anterograde induced amnesia to encoding failure by providing recall cues which were expected to eliminate retrograde amnesia but worsen or have no effect on anterograde amnesia. The 80 subjects received auditory presentation of 10 lists, each composed of 15 four-letter words presented at a rate of 2s/item at 75 dB in a free-recall task, followed by a 72 s recall period. The amnesia-producing event was an outstanding item in serial position 8 presented at 115 dB (about the intensity of a loud shout) on half the lists. During the first half of the recall period subjects free-recalled, but during the last half they were given a list of the first (single cue) or the first two (double cue) letters of each word, to be used as aids to recall. To demonstrate induced amnesia, lists containing a loud item were compared to those not containing one. First half free recall performance indicated that large retrograde and anterograde effects were present for both cue conditions. Second half cued recall performance indicated that in the double cue condition retrograde amnesia disappeared and anterograde amnesia became larger. Cueing had much smaller effects in the single cue condition.     

The effects of repeating a recognition test in lorazepam-induced amnesia: Evidence for impaired contextual memory as a cause of amnesia

In two experiments, a recognition test for an earlier presented list was given twice in immediate succession (Test 1 and Test 2). On the hypothesis that anterograde amnesia for episodic memory involves a deficit in contextual memory, amnesic subjects should confuse familiarity with distractor items gained during Test 1 with familiarity gained during original list presentation. As a result, they should think that they recognize more items on Test 2. This will lower recognition efficiency in Test 2 by increasing false alarms rather than by reducing hits. For subjects with an amnesia induced by lorazepam, but not for control subjects, recognition efficiency was substantially reduced in Test 2 in both experiments. As predicted, this impairment was due to a large increase in false alarms, with no decrease in the number of hits. The impairment could not be explained by a difference in recognition level between lorazepam and control subjects on Test 1. These findings therefore support the contextual memory deficit hypothesis of anterograde amnesia. Their implications for understanding the relationship between recall and recognition in amnesia are discussed.     

Backward associative strength determines source attributions given to false memories

Source attributions for falsely remembered material were investigated in two experiments. A male and a female speaker each presented either an entire word list or half of the items from each of multiple Deese-Roediger-McDermott (DRM) lists commonly used in this paradigm. In the latter condition the tendency of each list half to activate a nonpresented, critical list theme item was manipulated. All of the list halves differed in backward associative strength (BAS), and each was presented by one or the other of the two speakers. In these correlated conditions, when critical items were falsely recognized (Experiments 1 and 2) or recalled (Experiment 2), source attributions were more frequently made to the speaker of the list items with the higher average BAS. This source attribution effect appears to result from the binding of list item source characteristics to activated critical items during encoding, as opposed to being the result of a biased retrieval process. The results are interpreted as consistent with an activation/monitoring account of false memory in the DRM paradigm.     

Perceptual distinctiveness and proactive interference in the primacy effect

When subjects monitor a list of verbal items for one item which is to be selected and remembered, they are more likely to recall the critical item if it is the first member of the list than if it is presented towards the centre of the list. The present experiment examined the possibility that this primacy results from an accumulation of proactive interference from incidentally processed early members of the list which would cause a decrement in the recall of later members. By changing the semantic category of the list members before presentation of the critical item any accumulated interference would have been released, but this procedure produced no weakening of the primacy effect and so the interference theory of primacy was not supported. An alternative explanation of the effect was discussed in which it is assumed that the first member of a series is perceptually distinct from central members.     

The emotional carryover effect in memory for words

Emotional material rarely occurs in isolation; rather it is experienced in the spatial and temporal proximity of less emotional items. Some previous researchers have found that emotional stimuli impair memory for surrounding information, whereas others have reported evidence for memory facilitation. Researchers have not determined which types of emotional items or memory tests produce effects that carry over to surrounding items. Six experiments are reported that measured carryover from emotional words varying in arousal to temporally adjacent neutral words. Taboo, non-taboo emotional, and neutral words were compared using different stimulus onset asynchronies (SOAs), recognition and recall tests, and intentional and incidental memory instructions. Strong emotional memory effects were obtained in all six experiments. However, emotional items influenced memory for temporally adjacent words under limited conditions. Words following taboo words were more poorly remembered than words following neutral words when relatively short SOAs were employed. Words preceding taboo words were affected only when recall tests and relatively short retention intervals were used. These results suggest that increased attention to the emotional items sometimes produces emotional carryover effects; however, retrieval processes also contribute to retrograde amnesia and may extend the conditions under which anterograde amnesia is observed.     

Levels of processing: Qualitative differences or task-demand differences?

In nearly all reported orienting task studies, the question is asked before the item or items are presented. This paper reports two experiments wherein the question was asked after the item was presented. These experiments found that an orthographic orienting task did not produce poorer retention than a semantic orienting task when (1) the orthographic task was presented in such a way to ensure that the list items would be encoded as units and (2) the test was designed to eliminate the effect of encoding elaboration to positive-response orienting questions. It was concluded that the depth-of-processing effect was composed of two components. One of these is a task-demand component that affects the probability of encoding target items as identifiable units. The second component of processing depth is trace elaboration to positive-response questions. In most experiments, the two components combine to produce better memory performance for targets presented with semantic orienting questions. However, the two components can be examined independently of each other to determine the degree to which each contributes to a particular experimental effect.     

Monkey memory: same/different concept learning, serial probe acquisition, and probe delay effects

Three rhesus monkeys were trained and tested in a same/different task with six successive sets of 70 item pairs to an 88% accuracy on each set. Their poor initial transfer performance (55% correct) with novel stimuli improved dramatically to 85% correct following daily item changes in the training stimuli. They acquired a serial-probe-recognition (SPR) task with variable (1-6) item list lengths. This SPR acquisition, although gradual, was more rapid for the monkeys than for pigeons similarly trained. Testing with a fixed list length of four items at different delays between the last list item and the probe test item revealed changes in the serial-position function: a recency effect (last items remembered well) for 0-s delay, recency and primacy effects (first and last list items remembered well) for 1-, 2-, and 10-s delays, and only a primacy effect for the longest 30-s delay. These results are compared with similar ones from pigeons and are discussed in relation to theories of memory processing.     

High-priority event instructions affect implicit and explicit memory tests

Previous work has shown that instructing subjects to give special priority to one target event in a list enhances recall for that event, but impairs recall for the events immediately preceding it (Tulving, 1969). We examined the benefit of high-priority instructions, and the retrograde amnesia for previous items, in three experiments that included two explicit tests of memory (free recall and cued recall with word-stem cues) and an implicit test (word-stem completion). Experiments 1 and 2 revealed a beneficial effect of high-priority instructions on memory for the target events in both free recall and primed word-stem completion. Retrograde amnesia for previous events was either absent (Experiment 1) or modest (Experiment 2) in free recall; however, no evidence for amnesia occurred on the implicit test. In Experiment 3, we asked if the benefit of high-priority instructions on the implicit test was due to contamination from intentional recollection, by employing the logic of the retrieval-intentionality criterion via a levels-of-processing manipulation. The results showed a beneficial effect of high-priority instructions on free recall, word-stem cued recall, and word-stem completion. Level of processing affected the two explicit tests, but not the implicit test, indicating that it induced incidental retrieval. We conclude that the benefit of high-priority instructions occurred on all three tests used in these experiments. In contrast, the phenomenon of retrograde amnesia occurred in free recall, but not in primed word-stem completion.     

Two mechanisms in the stimulus suffix effect

The stimulus suffix is a redundant item presented immediately after a stimulus list. Its effect is the selective impairment of recall of the final items in a serially recalled, auditorily presented list of unconnected items. Two experiments indicate that there was no difference between the effects of suffixes .5 and 1.0 sec after the end of a digit list presented at a rate of one digit/sec. This suggests that the effect of the suffix, in this case the vowel sound "ah," is not a simple function of its time of arrival after the final digit, as has been thought. The possibility of more complex factors was supported in a further experiment which showed a slight reduction in the size of the suffix effect by repeating the suffix three times.     

Providing support for distinctive processing: the isolation effect in young and older adults

The isolation paradigm is the classic method for studying the effects of distinctiveness on memory (Hunt, 1995). Previous studies using the isolation paradigm with older adults (Bireta, Suprenant, & Neath, 2008; Cimbalo & Brink, 1982; Geraci, McDaniel, Manzano, & Roediger (2009); Vitali et al., 2006) placed the isolated items late in the study list. The current experiments, which are the first to investigate the isolation effect in young and older adults when the isolated item occurs early in the list, were motivated by a new framework for understanding age-related differences in the beneficial effects of distinctive processing. The framework, which is motivated by Hunt's (2006) discussion of distinctiveness and Craik's (1986) environmental support view, proposes that when contextual support is provided for the processing of both the difference and similarity components, older adults are more likely to show beneficial effects of distinctiveness. In Experiment 1, young adults showed both early and late isolation effects, while older adults showed only a late isolation effect. In the first experiment the isolated item was the word "table" in a list of fish names. In Experiment 2, the contrast between the isolated item and background items was increased by isolating numbers in a list of words. In the second experiment older adults, as well as young adults, showed an early isolation effect.     

Falsely recalled items are rich in item-specific information

Current theorizing suggests that critical lures in the Deese/Roediger-McDermott (DRM) procedure are often falsely remembered because they have received considerable relational processing (e.g., spreading activation or encoding of gist information). We used a repeated-testing paradigm to assess the amount of item-specific and relational processing given to the list items and the critical lures. Research has shown that items receiving item-specific processing are more likely to be recovered across successive tests. They are also output more slowly but more steadily throughout the recall period. In two experiments, we manipulated the processing performed on list items and then used item gains and cumulative recall curves to assess the amount of item-specific an drelational information encoded for both list items and lures. The results suggest that increasing the relational processing of list items increased item-specific processing of lures, whereas increasing item-specific processing of list items decreased item-specific processing of lures. We conclude that critical lures are typically rich in item-specific information, relative to list items.     

错误记忆的自我参照效应：易化的作用

采用DRM范式,设置三种参照对象条件（自我、他人和中性参照）,考察错误记忆是否存在自我参照效应。结果发现：（1）与正确记忆一样,错误记忆中亦存在自我参照效应;（2）无论是正确记忆还是错误记忆,自我参照条件下的回忆成分均显著多于他人参照和中性参照,但熟悉性成分在三种不同参照对象条件下没有显著差异;（3）当词表中学习项目由分组呈现变为随机呈现时,错误记忆的自我参照效应仍稳定存在。结果揭示,自我参照效在促进正确记忆的同时,亦可易化错误记忆效应。     

Selective interference with verbal short-term memory for serial order information: A new paradigm and tests of a timing-signal hypothesis

Many recent computational models of verbal short-term memory postulate a separation between processes supporting memory for the identity of items and processes supporting memory for their serial order. Furthermore, some of these models assume that memory for serial order is supported by a timing signal. We report an attempt to find evidence for such a timing signal by comparing an “item probe” task, requiring memory for items, with a “list probe” task, requiring memory for serial order. Four experiments investigated effects of irrelevant speech, articulatory suppression, temporal grouping, and paced finger tapping on these two tasks. In Experiments 1 and 2, irrelevant speech and articulatory suppression had a greater detrimental effect on the list probe task than on the item probe task. Reaction time data indicated that the list probe task, but not the item probe task, induced serial rehearsal of items. Phonological similarity effects confirmed that both probe tasks induced phonological recoding of visual inputs. Experiment 3 showed that temporal grouping of items during list presentation improved performance on the list probe task more than on the item probe task. In Experiment 4, paced tapping had a greater detrimental effect on the list probe task than on the item probe task. However, there was no differential effect of whether tapping was to a simple or a complex rhythm. Overall, the data illustrate the utility of the item probe/list probe paradigm and provide support for models that assume memory for serial order and memory for items involve separate processes. Results are generally consistent with the timing-signal hypothesis but suggest further factors that need to be explored to distinguish it from other accounts.     

The role of visual interference in producing the long-term modality effect

Typically, recall of the last of a list of auditory items greatly exceeds recall of the last of a list of visual items. This modality effect has been found in serial recall, free recall, and recall using the distractor paradigm in which each to-be-remembered item is preceded and followed by distractor activity. One source of the auditory advantage may be visual interference that reduces recall of visual stimuli. In three experiments, sources of visual interference were minimized. Although this manipulation reduced the modality effect, it did not eliminate the effect.     

Revisiting von Restorff’s early isolation effect

An item that is conceptually or physically different from other items in a series is often remembered well. This isolation effect has been found independent of the position of the isolated item in the list, suggesting that special attention to or processing of the isolated item is not a necessary precondition of the effect. Three experiments are reported that challenge this conclusion. In Experiment 1a, we compared memory for conceptually isolated items to memory for the same items in unrelated and homogeneous lists. Under moderately distracting conditions, isolation effects were observed with midlist but not with early isolates. In fact, early isolation impaired memory for the conceptually distinct items relative to the same items in homogeneous lists. Experiment 1b replicated this memory impairment for early conceptual isolates and extended it to nondistracting conditions. In Experiment 2, we focused on early isolation, manipulating the type of isolation and whether or not participants performed judgments of learning (JOLs). An early isolation effect was observed for numbers isolated in lists of words (and vice versa), but not for conceptual isolates. Performing the JOL task reduced the size of the early isolation effect. These results suggest that number/word stimulus contrasts are coded automatically and support an isolation effect independent of list position. However, conceptual contrasts require relational processing and will only support an early isolation effect when such processing occurs. The results of Experiments 1a, 1b, and 2 suggest that attentional resources during list presentation and a favorable retrieval environment combine to support good memory for distinctive events.     

False recognition following study of semantically related lists presented in jumbled word form

Three experiments explored a jumbled word effect in false recognition. Lists of theme-related items were presented in word or nonword form. Results indicated that critical lures semantically related to studied items were falsely recognised regardless of whether they were presented as words or nonwords. High false recognition rates to either SLEEP or SELEP following study of an appropriate theme list of items in nonword form should only occur if nonwords are recoded at study. With study conditions conducive to recoding, jumbled words induced false recognitions based on semantic associations among their respective base words. Disrupting a recoding process by creating "difficult" letter rearrangements for jumbled words (Experiment 2) appeared to eliminate the false recognition effect. In Experiment 3, presentation durations ranged from 110 ms to 880 ms. Although there was little evidence of a semantic false recognition effect at the fastest presentation rate, the brief durations appeared to be effective in eliminating the effect when items were studied in nonword form. These results appear to be consistent with an encoding activation/retrieval monitoring model.     

A bias interpretation of facilitation in perceptual identification

In a typical perceptual identification task, a word is presented for a few milliseconds and masked; then subjects are asked to report the word. It has been found that an earlier presentation of the test word will improve identification of the test word by as much as 30%. In addition, this facilitation has been shown to be preserved under amnesia. In this article we examine a fundamental question: Is the facilitation the result of bias toward the earlier presented item, an improvement in perceptual sensitivity, or both? The experiments presented here use a forced choice procedure to show that prior presentation of an item biases the subject to choose that item but does not improve discriminability. This result is obtained when the distractor items are visually similar to the target items. When distractors are dissimilar, earlier presentation affects neither bias nor discriminability. Two models of word identification are examined in light of the bias effects, and implications for understanding savings in amnesia are also examined.     

The Isolation, Primacy, and Recency Effects Predicted by an Adaptive LTD/LTP Threshold in Postsynaptic Cells

An item that stands out (is isolated) from its context is better remembered than an item consistent with the context. This isolation effect cannot be accounted for by increased attention, because it occurs when the isolated item is presented as the first item, or by impoverished memory of nonisolated items, because the isolated item is better remembered than a control list consisting of equally different items. The isolation effect is seldom experimentally or theoretically related to the primacy or the recency effects—that is, the improved performance on the first few and last items, respectively, on the serial position curve. The primacy effect cannot easily be accounted for by rehearsal in short-term memory because it occurs when rehearsal is eliminated. This article suggests that the primacy, the recency, and the isolation effects can be accounted for by experience-dependent synaptic plasticity in neural cells. Neurological empirical data suggest that the threshold that determines whether cells will show long-term potentiation (LTP) or long-term depression (LTD) varies as a function of recent postsynaptic activity and that synaptic plasticity is bounded. By implementing an adaptive LTP-LTD threshold in an artificial neural network, the various aspects of the isolation, the primacy, and the recency effects are accounted for, whereas none of these phenomena are accounted for if the threshold is constant. This theory suggests a possible link between the cognitive and the neurological levels.     

Decline in working memory updating through ageing: intrusion error analyses

The present research examines the decline in working memory updating through age. Two experiments compared groups of participants in different age ranges (young-old, 55-65 years, old, 66-75 years and old-old, more than 75 years and, in Experiment 2 only, young, 20-30 years). Memory updating tasks were administered, which required participants to remember the smallest items in each list. To perform the task correctly, participants had to update information efficiently, reducing interference from items no longer relevant. Intrusion errors were computed and in the first experiment these were described as "intrusions of irrelevant items" (immediate exclusion) and "intrusions of once relevant items" (delayed exclusion). The oldest adults performed worse in memory updating and made a greater number of intrusion errors of once relevant information. In the second experiment results showed that increases in memory load (number of items that had to be remembered) and updating demand (number of potentially relevant items) impaired performance. The oldest adults had greater difficulty when the task demand was increased. Furthermore, they produced a higher number of intrusion errors, particularly when the updating demand was increased. It therefore appears that elderly people have specific difficulty in updating information in working memory by excluding irrelevant information.     

Word frequency effects in immediate serial recall: Item familiarity and item co‐occurrence have the same effect

In immediate serial recall, high‐frequency words are better recalled than low‐frequency words. A prevalent interpretation of this effect suggests that, at the point of recall, degraded representations undergo a reconstruction process calling upon long‐term knowledge of the to‐be‐remembered items. Recently, Stuart and Hulme () following Deese (), suggested that high‐frequency items are better recalled due to their better long‐term associative links. Their results revealed that a familiarisation procedure involving repeated presentations of the to‐be‐remembered items in pairs abolished the usual frequency effect. In the experiment reported here, an alternative interpretation of this result is examined. Prior to the memory task, subjects received either no familiarisation, item familiarisation, or pair familiarisation. Both item and pair familiarisation improved the item recall of low‐frequency items to the same extent, suggesting that increased familiarity can account for the co‐occurrence effect.