Proactive interference in immediate serial recall

Two experiments yielded significant inter-list proactive interference (PI) in immediate serial recall of nine-consonants lists. This argues against the assumption that intra-trial rehearsal is sufficiently powerful to prevent PI from occurring. In the first experiment PI proved to be more pronounced in the case of visually than of auditorily presented lists to the extent that the modality effect on the prerecent items could be completely attributed to PI. PI also enlarged the effect of output interference through reversed order recall. These findings were confirmed in the second experiment which also showed that the effect of PI persisted at a slower presentation rate, suggesting that the role of rehearsal in counteracting PI should not be overestimated. Implications of these results for current notions on short-term retention are discussed.     

Comparing Short-term Memory and Memory for Rapidly Presented Visual Stimuli

What similarities and differences are there between memory for short lists shown at one item per second and memory for such lists after rapid serial visual presentation (RSVP) at much higher rates—eight items per second? This paper reports that, when pictures are shown at eight per second or one per second, phonological similarity of the picture names reduces recall at the one item per second rate, but not at the eight item per second rate. In contrast, when subjects are shown the written names of the pictures, phonological similarity reduces recall at both rates. It is concluded that phonological coding does not occur for picture lists shown at high rates. The mechanisms underlying memory for pictures and words shown at RSVP and short-term memory rates are considered.     

Word frequency effects in immediate serial recall of pure and mixed lists: tests of the associative link hypothesis.

In immediate serial recall, high-frequency words are better recalled than low-frequency words. Recently, it has been suggested that high-frequency words are better recalled because of their better long-term associative links, and not because of the intrinsic properties of their long-term representations. In the experiment reported here, recall performance was compared for pure lists of high- and low-frequency words, and for mixed lists composed of either one low- and five high-frequency words or the reverse. The usual advantage of high-frequency words was found with pure lists and this advantage was reduced, but still significant with mixed lists composed of five low-frequency words. However, the low-frequency word included in a high-frequency list was recalled just as well as high-frequency words. Results are challenging for the associative link hypothesis and are best interpreted within an item-based reconstruction hypothesis, along with a distinctiveness account.     

Articulatory suppression and the grouping of successive stimuli

Summary Two experiments required subjects to memorise for immediate recall lists of nine items, presented visually and grouped by threes. As each item followed the previous one in the same spatial location, it must have been temporarily stored until the whole group had arrived. In one experiment the items were digits; grouping could be detected by the fact that recall of the last two items in a group was heavily contingent upon recall of the first item. In the second experiment the items were letters, and some of the lists were made up of meaningful triplets of letters such as UNO. Grouping could be detected by the size of the difference between these lists and the meaningless ones. In each experiment, the extent of grouping was just as great if the subjects were asked to repeat an irrelevant sequence of sounds while memorising; although the recall under both conditions was of course depressed.It appears therefore that the temporary memory, in which the items are held before grouping, is not impaired by articulatory suppression; nor in these conditions could it have been a sensory store. The result is supportive evidence for the existence of an abstract, non-sensory, non-motor, working memory.Both authors are employed, and their research supported, by the Medical Research Council     

The influence of acoustic similarity on serial recall of letter sequences

Acoustic similarity is known to impair short-term memory (STM) for letter sequences. The present series of experiments investigated the effects of acoustic similarity on long-term retention. In the first experiment, subjects were asked to learn one of two lists of 8 letters, the letters being either of high or low acoustic similarity. Lists were visually presented for three trials, with subjects responding after each trial. Then subjects participated in an immediate memory task for digits which lasted for 20 min. Finally, subjects tried to recall the list of letters they had learned previously. Lists having items of high acoustic similarity were more difficult to recall on the first trial, but were better recalled on the delayed retention test. In a second experiment, groups of subjects were again asked to learn one of two lists of 8 letters differing in acoustic similarity, using different orders of the letters used previously. The procedures were identical except that in two groups, a STM task for digits intervened between the presentation and test of the letters. This intervening task minimized the effects of STM and eliminated the differences in retention found previously. In a third experiment, better long-term retention for material having high acoustic similarity was also obtained when subjects used a backward recall procedure. In the last experiment 14 item lists were learned to a criterion of two correct trials, and retention was tested after each trial and at a delay of 20 min. and 23 hr. No effect of acoustic similarity was found and little retention loss occurred. These results suggest that reducing the STM component by introducing a STM control or by lengthening the list caused the effect of acoustic similarity to disappear.     

Serial reconstruction of order and serial recall in verbal short-term memory

We carried out a series of experiments on verbal short-term memory for lists of words. In the first experiment, participants were tested via immediate serial recall, and word frequency and list set size were manipulated. With closed lists, the same set of items was repeatedly sampled, and with open lists, no item was presented more than once. In serial recall, effects of word frequency and set size were found. When a serial reconstruction-of-order task was used, in a second experiment, robust effects of word frequency emerged, but set size failed to show an effect. The effects of word frequency in order reconstruction were further examined in two final experiments. The data from these experiments revealed that the effects of word frequency are robust and apparently are not exclusively indicative of output processes. In light of these findings, we propose a multiple-mechanisms account in which word frequency can influence both retrieval and preretrieval processes.     

Influence of marihuana on storage and retrieval processe in memory

Following presentation and immediate free recall testing of 10 20-word lists, 48 Ss were divided into two groups, one of which received an oral dose of marihuana extract calibrated to 20 mg of Δ¹-THC and one of which received placebo. One hour later, all Ss were administered delayed recall, recognition, and order tests on the first set of words. Presentation of another set of 10 lists followed, and there were immediate recall and delayed recall, recognition, and order tests on these words. Performance of drug and placebo Ss did not differ significantly for any of the first delayed tests. However, the performance of drug Ss was poorer than that of placebo Ss on immediate recall, delayed recall, and delayed recognition of the second set of lists. We concluded that retrieval of information relevant to the occurrence or nonocurrence of an event was not affected by marihuana intoxication. Storage difficulties probably account for memory deficits due to the drug, and these difficulties appear to occur in the process of transferring information from short-term to long-term memory.     

Normal acquisition of novel verbal information in amnesia.

Amnesic patients (n = 9) and normal subjects (n = 12) read lists of unique words, repeated words, unique nonwords, and repeated nonwords as quickly as possible. In the first experiment both groups of subjects read the lists of repeated items faster than the lists of unique items and improved at the same rate within each list. In the second experiment, subjects read four new lists of items and then reread the same four lists after a 10-min delay. The results replicated the findings from the first experiment and demonstrated in addition that the facilitated reading speed persisted across the delay. These results show that the acquisition of novel verbal information can be supported by nondeclarative (implicit) memory. It is suggested that facilitated reading speed for words and nonwords reflects changes in early-stage perceptual systems and that these changes occur independently of the brain structures damaged in amnesia.     

The bizarre mnemonic

Summary Five experiments measured effects of bizarre contexts on the free recall of noun triplets after brief retention intervals. More triplets were remembered from bizarre than from common contexts in short mixed lists (12 sentences) when the sentences were presented at a controlled (10 seconds/sentence) rate, regardless of incidental task (rating images for bizarreness, vividness, or memorability). The average number of words/sentence recalled, however, tended to be higher for common than for bizarre contexts. No memory benefit from bizarreness was found for pure lists nor for lists containing more than six triplets in bizarre contexts. The bizarreness effect was less when the subject controlled the rate of presentation. A sixth experiment, which tested recall after immediate and two-day retention intervals, found that the Bizarre/Common Context by Pure/Mixed List interaction increased over longer retention intervals.     

Lexical and semantic influences on item and order memory in immediate serial recognition: Evidence from a novel task

Previous studies have reported that, in contrast to the effect on immediate serial recall, lexical/semantic factors have little effect on immediate serial recognition. This has been taken as evidence that linguistic knowledge contributes to verbal short-term memory in a redintegrative process at recall. Contrary to this view, we found that lexicality, frequency, and imageability all influenced matching span. The standard matching span task, requiring changes in item order to be detected, was less susceptible to lexical/semantic factors than was a novel task involving the detection of phoneme order and hence item identity changes. Therefore, in both immediate recognition and immediate serial recall, lexical/semantic knowledge makes a greater contribution to item identity than to item order memory. Task sensitivity, and not the absence of overt recall, may have underpinned previous failures to show effects of these variables in immediate recognition. We also compared matching span for pure and unpredictable mixed lists of words and nonwords. Lexicality had a larger impact on immediate recognition for pure than for mixed lists, in line with findings for immediate serial recall. List composition affected the detection of phoneme but not item order changes in matching span; similarly, in recall, mixed lists produce more frequent word phoneme migrations but not migrations of entire items. These results point to strong similarities between immediate serial recall and recognition. Lexical/semantic knowledge may contribute to phonological stability in both tasks.     

Lexical and semantic influences on item and order memory in immediate serial recognition: evidence from a novel task

Previous studies have reported that, in contrast to the effect on immediate serial recall, lexical/semantic factors have little effect on immediate serial recognition. This has been taken as evidence that linguistic knowledge contributes to verbal short-term memory in a redintegrative process at recall. Contrary to this view, we found that lexicality, frequency, and imageability all influenced matching span. The standard matching span task, requiring changes in item order to be detected, was less susceptible to lexical/semantic factors than was a novel task involving the detection of phoneme order and hence item identity changes. Therefore, in both immediate recognition and immediate serial recall, lexical/semantic knowledge makes a greater contribution to item identity than to item order memory. Task sensitivity, and not the absence of overt recall, may have underpinned previous failures to show effects of these variables in immediate recognition. We also compared matching span for pure and unpredictable mixed lists of words and nonwords. Lexicality had a larger impact on immediate recognition for pure than for mixed lists, in line with findings for immediate serial recall. List composition affected the detection of phoneme but not item order changes in matching span; similarly, in recall, mixed lists produce more frequent word phoneme migrations but not migrations of entire items. These results point to strong similarities between immediate serial recall and recognition. Lexical/semantic knowledge may contribute to phonological stability in both tasks.     

Children's emotional false memories

Eight- and 12-year-old children were presented with neutral and negative emotional Deese-Roediger-McDermott lists equated on familiarity and associative strength. Both recall and recognition (A') measures were obtained. Recall measures exhibited the usual age increments in true and false recollection. True neutral items were better recalled and recognized than true negative emotional items. Although the children showed more false recall for neutral than for negative emotional lists, false recognition was higher for negative emotional than for neutral items. A' analyses also showed that whereas true neutral information and false neutral information were easily discriminated by children regardless of age, the same was not the case for true and false negative emotional information. Together, these results suggest that although children may be able to censor negative emotional information at recall, such information promotes relational processing in children's memory, making true and false emotional information less discriminable overall.     

Short-term memory capacity: magic number or magic spell?

Previous experiments have found that memory span is greater for items that can be pronounced more quickly. For a variety of materials the span equals the number of items that can be pronounced in about 1.5 s, presumably the duration of the verbal trace. This suggests a model for immediate recall: The probability of correctly recalling a list equals the probability that the time to recite the list is less than the variable duration of the trace. Recall probability for lists of various lengths was determined for six materials. Later, subjects read the lists aloud. The standard normal deviates corresponding to probability of correct recall were linear in pronunciation time. Evidently, over subjects, a normal distribution is a reasonable approximation of the distribution of the trace duration. The mean and variance of the trace duration were estimated. The mean (1.88 s) agrees well with previous estimates, and the model accounts for 95% of the variance in immediate recall.     

Recall accuracy and illusory memories: when more is less

In two experiments it was revealed that manipulations that increased recall of studied list items also increased false recall of theme-related, critical nonpresented words. In Experiment 1 subjects listened to a series of short word lists, each containing items associatively related to a theme, while engaging in either semantic or nonsemantic processing. On an immediate free recall test semantic processors demonstrated greater correct recall as well as more illusory memories of critical nonpresented items than nonsemantic processors. In Experiment 2, the short study lists were combined to form longer lists that were presented either blocked by theme or in a random presentation order. Retention interval was also varied as participants were tested either immediately, one week after, or three weeks after the study phase. Presenting the target items in a blocked, as opposed to random, format increased recall accuracy, but this was at the expense of a higher intrusion rate for theme-consistent items. Interestingly, the level of false memories was not affected by retention interval even though typical decrements in the recall of study items were observed over time. The results of these experiments highlight the persistence of the false memory effect, as well as pointing to several factors, primarily semantic processing, that may lead to the creation of false memories. Interpretations are offered within the theoretical frameworks of source monitoring and fuzzy trace theory.     

The contributions of encoding,retention, and recall to the Hebb effect

The article reports an experiment testing whether the Hebb repetition effect—the gradual improvement of immediate serial recall when the same list is repeated several times—depends on overt recall of the repeated lists. Previous reports which suggest that recall is critical confound the recall manipulation with retention interval. The present experiment orthogonally varies retention interval (0 or 9 s) and whether the list is to be recalled after the retention interval. Hebb repetition learning is assessed in a final test phase. A repetition effect was obtained in all four experimental conditions; it was larger for recalled than non-recalled lists, whereas retention interval had no effect. The results show that encoding is sufficient to generate cumulative long-term learning, which is strengthened by recall. Rehearsal, if it takes place in the retention interval at all, does not have the same effect on long-term learning as overt recall.     

Phonological Similarity and Trace Degradation in the Serial Recall Task: When CAT helps RAT,but not MAN

Phonological similarity is observed to affect serial recall detrimentally when correct-in-position scoring is used. Two experiments investigated the role of item and position accuracy scoring of rhyming, similar nonrhyming, and dissimilar lists under immediate recall conditions; articulatory suppression; or a filled delay. In general, rhyme lists produced the best item recall but position accuracy was highest for dissimilar lists. The results are due to a category cueing effect improving item recall for rhyme lists in conjunction with a detrimental effect of phonological similarity on position accuracy.     

Effects of list organization and retrieval cues on children's delayed recall.

Developmental differences in recall were investigated as a function of mode of presentation (blocked vs. random), recall condition (cued vs. noncued), and time of recall (immediate vs. delayed). Ninety-six second graders and 96 fourth graders were the subjects, and the stimuli were 20 pictured items from five categories. Data on three dependent variables (item recall, category recall, and clustering score) were analyzed. Immediate recall was better than delayed recall, the fourth graders' overall performance was superior to that of the second graders, and the blocked presentation of items and the presence of retrieval cues at recall enhanced recall and organization in recall. Furthermore, an analysis of a three-way interaction on two dependent measures indicated that, in the noncued condition, immediate recall was better than delayed recall for children in both grades. However, in the cued condition, the fourth graders performed better during delayed recall than during immediate recall, whereas the second graders did better during immediate recall than during delayed recall.     

Advantages and disadvantages of phonological similarity in serial recall and serial recognition of nonwords

The phonological similarity effect (PSE) was studied with lists of nonwords in one task of serial recall and one task of serial recognition. PSE was critically affected by the scoring procedure and the type of phonological similarity involved, and the effect diverged in several ways from the findings of previous studies on words. PSE was absent in serial recall, regardless of scoring procedure, when phonologically similar items that shared the midvowel were compared with phonologically distinct items. PSE was reversed when serial recall and item recall scores of rhyme items and consonant frame items were compared with distinct items, but it was present in the position accuracy score of rhyme lists. In serial recognition, PSE was absent when rhyme lists were compared with distinct lists. Recognition was better for consonant frame lists than for rhyme lists, and there was a marginally significant reversal of PSE when consonant frame lists were compared with distinct lists. In the view of Fallon, Groves, and Tehan's (1999) study and the present study, rhyming improves item recall and serial recall but diminishes position accuracy, regardless of lexicality. But consonant frame lists with differing midvowels have higher item recall, serial recall, and position accuracy scores than do rhyme lists.     

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.     

Word frequency and the mixed-list paradox in immediate and delayed serial recall

In free recall tasks, when low- and high-frequency items are mixed within the to-be-remembered lists, the usual recall advantage found for high-frequency words is eliminated or reversed. Recently, this mixedlist paradox has also been demonstrated for short-term serial recall (Hulme, Stuart, Brown, & Morin, 2003). Although a number of theoretical interpretations of this mixed-list paradox have been proposed, researchers have also suggested that it could simply be a result of participant-controlled strategies (M. J. Watkins, LeCompte, & Kim, 2000). The present study was designed to assess whether this explanation could be applied to immediate and delayed serial recall. The results showed that high-frequency words were recalled better than low-frequency words in pure lists, but that this effect was eliminated in mixed lists, whether they were given under intentional or incidental learning conditions. This pattern suggests that the mixed-list paradox cannot be explained by participant-controlled strategies.