A multinomial processing tree model for degradation and redintegration in immediate recall

When items are presented for immediate recall, a verbal trace is formed and degrades quickly, becoming useless after about 2 sec. The span for items such as digits equals the number of items that canbe pronounced in the available time. The length of the items affects span by affecting pronunciation rate. Other properties, such as phonological similarity and lexicality, can affect span without affecting pronunciation rate. These properties change the trace's useful lifetime by affecting redintegration. An analogy is drawn between trace reconstruction and repair of errors in speech. When a trace is degraded, one process attempts to form a phoneme string, and another process attempts to form a word. The two processes are autonomous and can be selectively influenced by lexicality and phonological similarity. The resulting processing tree models make simple predictions that depend on whether or not the influenced processes are sequential. The results are illustrated with data from experiments by Besner and Davelaar (1982).     

An attractor network model of serial recall

We present a neural network model of verbal working memory which attempts to illustrate how a few simple assumptions about neural computation can shed light on cognitive phenomena associated with the serial recall of verbal material. We assume that neural representations are distributed, that neural connectivity is massively recurrent, and that synaptic efficacy is modified based on the correlation between pre- and post-synaptic activity (Hebbian learning). Together these assumptions give rise to emergent computational properties that are relevant to working memory, including short-term maintenance of information, time-based decay, and similarity-based interference. We instantiate these principles in a specific model of serial recall and show how it can both simulate and explain a number of standard cognitive phenomena associated with the task, including the effects of serial position, word length, articulatory suppression (and its interaction with word length), and phonological similarity.     

An endogenous distributed model of ordering in serial recall

We introduce a distributed model of memory for serial order, called SOB, that produces ordered serial recall by relying on encoding and retrieval processes that are endogenous to the model. SOB explains the basic shape of the serial position curve, the pattern of errors during recall (including the balance between transpositions, omissions, intrusions, and erroneous repetitions), the effects of list length on the distribution of errors, the overall level of recall and response latency, and the effects of natural language frequency on recall performance. In addition, contrary to several recent suggestions, SOB demonstrates that distributed representations can support unambiguous recall, selective response suppression, and novelty-sensitive encoding.     

Rehearsal in immediate serial recall

We report for the first time overt rehearsal data in immediate serial recall (ISR) undertaken at three presentation rates (1, 2.5, and 5 sec/word). Two groups of participants saw lists of six words for ISR and were required either to engage in overt rehearsal or to remain silent after reading aloud the word list during its presentation. Typical ISR serial position effects were obtained for both groups, and recall increased with slower rates. When participants rehearsed, they tended to do so in a cumulative forward order up to Serial Position 4, after which the amount of rehearsal decreased substantially. There were similarities between rehearsal and recall data: Both broke down toward the end of longer sequences, and there were strong positive correlations between the maximum sequence of participants' rehearsals and their ISR performance. We interpret these data as suggesting that similar mechanisms underpin both rehearsal and recall in ISR.     

A comparative analysis of serial and free recall

Multitrial free and serial recall tasks differ both in recall instruction and in presentation order across trials. Waugh (1961) compared these paradigms with an intermediate condition: free recall with constant presentation order. She concluded that differences between free and serial recall were due only to recall instructions, and not to presentation order. The present study reevaluated the relation between free and serial recall, using Waugh's three conditions. By examining recall transitions and the organization of information retained across trials, we conclude that presentation order is an important factor, causing participants to exhibit the same temporal associations in serial recall and in free recall with constant presentation order.     

Transposition asymmetry in immediate serial recall

When participants confuse the position of items in immediate serial recall, they tend to recall transposed items too early rather than too late. This asymmetry of transposition errors was observed in four experiments. It increased as a function of list length, but was independent of report order, output position, cueing condition, and recall mode. The transposition asymmetry is consistent with error patterns in free recall and in regular speech production where transpositions are usually forward‐looking. The asymmetry of transposition errors is discussed in terms of models of serial memory.     

Output order in immediate serial recall

In two experiments, we examined the effect of output order in immediate serial recall (ISR). In Experiment 1, three groups of participants saw lists of eight words and wrote down the words in the rows corresponding to their serial positions in an eight-row response grid. One group was precued to respond in forward order, a second group was precued to respond in any order, and a third group was postcued for response order. There were significant effects of output order, but not of cue type. Relative to the forward output order, the free output order led to enhanced recency and diminished primacy, with superior performance for words output early in recall. These results were replicated in Experiment 2 using six-item lists, which further suggests that output order plays an important role in the primacy effect in ISR and that the recency items are most highly accessible at recall.     

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.     

Transposition asymmetry in immediate serial recall

When participants confuse the position of items in immediate serial recall, they tend to recall transposed items too early rather than too late. This asymmetry of transposition errors was observed in four experiments. It increased as a function of list length, but was independent of report order, output position, cueing condition, and recall mode. The transposition asymmetry is consistent with error patterns in free recall and in regular speech production where transpositions are usually forward-looking. The asymmetry of transposition errors is discussed in terms of models of serial memory.     

Overwriting of phonemic features in serial recall

We tested two explanations of the phonological similarity effect in verbal short‐term memory: The confusion hypothesis assumes that serial positions of similar items are confused. The overwriting hypothesis states that similar items share feature representations, which are overwritten. Participants memorised a phonologically dissimilar list of CVC‐trigrams (Experiment 1) or words (Experiment 2 and 3) for serial recall. In the retention interval they read aloud other items. The material of the distractor task jointly overlapped one item of the memory list. The recall of this item was impaired, and the effect was not based on intrusions from the distractor task alone. The results provide evidence for feature overwriting as one potential mechanism contributing to the phonological similarity effect.     

Overwriting of phonemic features in serial recall

We tested two explanations of the phonological similarity effect in verbal short-term memory: The confusion hypothesis assumes that serial positions of similar items are confused. The overwriting hypothesis states that similar items share feature representations, which are overwritten. Participants memorised a phonologically dissimilar list of CVC-trigrams (Experiment 1) or words (Experiment 2 and 3) for serial recall. In the retention interval they read aloud other items. The material of the distractor task jointly overlapped one item of the memory list. The recall of this item was impaired, and the effect was not based on intrusions from the distractor task alone. The results provide evidence for feature overwriting as one potential mechanism contributing to the phonological similarity effect.     

Immediate serial recall of mixed-modality lists

Seven experiments are reported in which subjects were tested for immediate serial recall of mixed-modality lists. On mixed auditory-visual lists, there was an advantage for auditory items at all serial positions. This was due to both a facilitation of auditory items and an inhibition of visual items on mixed lists, as compared with single-modality lists. When presented on a list containing items read silently, recall of items that were silently mouthed by the subject demonstrated patterns similar to those found with auditory items. When presented on a list containing items read aloud, recall of mouthed items showed patterns similar to those found with silently read items. The auditory advantage on mixed lists was found even when the list items were acoustically similar or identical and was not reduced by midlist auditory suffixes. The results suggest that modality differences in recall of mixed-modality lists are based on information different from that responsible for modality differences in recall of single-modality lists.     

Inverting the modality effect in serial recall

Differences in recall ability between immediate serial recall of auditorily and visually presented verbal material have traditionally been considered restricted to the end of to-be-recalled lists, the recency section of the serial position curve (e.g., Crowder & Morton, 1969). Later studies showed that--under certain circumstances--differences in recall between the two modalities can be observed across the whole of the list (Frankish, 1985). However in all these studies the advantage observed is for recall of material presented in the auditorily modality. Six separate conditions across four experiments demonstrate that a visual advantage can be obtained with serial recall if participants are required to recall the list in two distinct sections using serial recall. Judged on a list-wide basis, the visual advantage is of equivalent size to the auditory advantage of the classical modality effect. The results demonstrate that differences in representation of auditory and visual verbal material in short-term memory persist beyond lexical and phonological categorization and are problematic for current theories of the modality effect.     

Examining the relationship between free recall and immediate serial recall: The serial nature of recall and the effect of test expectancy

In two experiments, we examined the relationship between free recall and immediate serial recall (ISR), using a within-subjects (Experiment 1) and a between-subjects (Experiment 2) design. In both experiments, participants read aloud lists of eight words and were precued or postcued to respond using free recall or ISR. The serial position curves were U-shaped for free recall and showed extended primacy effects with little or no recency for ISR, and there was little or no difference between recall for the precued and the postcued conditions. Critically, analyses of the output order showed that although the participants started their recall from different list positions in the two tasks, the degree to which subsequent recall was serial in a forward order was strikingly similar. We argue that recalling in a serial forward order is a general characteristic of memory and that performance on ISR and free recall is underpinned by common memory mechanisms.     

A dynamic generalization of the Rasch model

In the present paper a model for describing dynamic processes is constructed by combining the common Rasch model with the concept of structurally incomplete designs. This is accomplished by mapping each item on a collection of virtual items, one of which is assumed to be presented to the respondent dependent on the preceding responses and/or the feedback obtained. It is shown that, in the case of subject control, no unique conditional maximum likelihood (CML) estimates exist, whereas marginal maximum likelihood (MML) proves a suitable estimation procedure. A hierarchical family of dynamic models is presented, and it is shown how to test special cases against more general ones. Furthermore, it is shown that the model presented is a generalization of a class of mathematical learning models, known as Luce's beta-model.     

Associative asymmetry in probed recall of serial lists

For pairs of meaningful items (e.g., words), recall accuracy is nearly identical for forward and backward probes. That is, after studying an A-B pair, subjects can recall A given B as well as they can recall B given A (Kahana, 2002). To assess whether this symmetry property is unique to pairs, we investigated the effects of study direction on probed recall of word triples and serial lists. Two experiments revealed a forward-recall advantage in both triples and serial lists. In addition, compound cues produced better recall than did single-item adjacent cues, which, in turn, produced better recall than did remote cues. These findings suggest a discontinuity between the associative processes supporting memory for pairs and those supporting memory for sequences of three or more items.     

Phonological and semantic strategies in immediate serial recall

It has been suggested that certain theoretically important anomalous results in the area of verbal short-term memory could be attributable to differences in strategy. However there are relatively few studies that investigate strategy directly. We describe four experiments, each involving the immediate serial recall of word sequences under baseline control conditions, or preceded by instruction to use a phonological or semantic strategy. Two experiments varied phonological similarity at a presentation rate of one item every 1 or 2 seconds. Both the control and the phonologically instructed group showed clear effects of similarity at both presentation rates, whereas these were largely absent under semantic encoding conditions. Two further experiments manipulated word length at the same two rates. The phonologically instructed groups showed clear effects at both rates, the control group showed a clear effect at the rapid rate which diminished with the slower presentation, while the semantically instructed group showed a relatively weak effect at the rate of one item per second, and a significant reverse effect with slower presentation. The latter finding is interpreted in terms of fortuitous differences in inter-item rated associability between the two otherwise matched word pools, reinforcing our conclusion that the semantically instructed group were indeed encoding semantically. Implications for controlling strategy by instruction are discussed.     

Temporal isolation effects in recognition and serial recall

Recent temporal distinctiveness models of memory predict that temporally isolated items will be recalled better than temporally crowded items. The effect has been found in some tasks (free recall, memory for serial order when report order is unconstrained, running memory span) but not in others (forward serial recall). Such results suggest that the attentional weighting given to a temporal dimension in memory may vary with task demands. Here, we find robust temporal isolation effects in recognition memory (Experiment 1) and a smaller isolation effect in forward serial recall when an open pool of items is used (Experiment 2). Analysis of 26 temporal isolation effects suggests that the phenomenon occurs in a range of tasks but is larger when it is useful to attend to a temporal dimension in memory. The overall pattern of results is taken to favor memory models that rely on multiple weighted dimensions in memory, one of which is temporal.