Speech Rate Estimates,Language of Schooling and Bilingual Digit Span

Bilinguals obtain larger digit spans in the language in which speech rate is fastest. This effect is generally interpreted as support for a central tenet of working memory theory, which proposes subvocal rehearsal rate as an influential determinant of memory span. Variation in the method of speech rate estimation, however, has been high, making comparison between studies difficult. In the present study, we compared the predictive power of three estimates of speech rate in relation to auditory digit span for two distinct bilingual types across nine school grades (1–9). One type spoke Swedish in the home and school (SS), the other spoke Finnish in the home and Swedish at school (FS). The results showed SS consistently obtained faster speech rates in Swedish, whereas FS obtained shorter articulation and numeral reading times in Swedish, as did grades 1–3 on a digit word reading task. However, FS grades 4–9 obtained equivalent digit word reading times between the languages. SS obtained a larger digit span in Swedish than Finnish, whereas FS obtained an equivalent digit span between the languages. Thus the results indicated that memory span was mediated by factors other than phonological loop functioning, as articulation time did not predict memory span performance for FS. The finding that FS obtained lower digit spans in Swedish relative to SS suggested that the former were disadvantaged in the processing of digits compared to native speakers of the language of schooling.     

Speech timing and working memory in profoundly deaf children after cochlear implantation

Thirty-seven profoundly deaf children between 8- and 9-years-old with cochlear implants and a comparison group of normal-hearing children were studied to measure speaking rates, digit spans, and speech timing during digit span recall. The deaf children displayed longer sentence durations and pauses during recall and shorter digit spans compared to the normal-hearing children. Articulation rates, measured from sentence durations, were strongly correlated with immediate memory span in both normal-hearing and deaf children, indicating that both slower subvocal rehearsal and scanning processes may be factors that contribute to the deaf children's shorter digit spans. These findings demonstrate that subvocal verbal rehearsal speed and memory scanning processes are not only dependent on chronological age as suggested in earlier research by. Instead, in this clinical population the absence of early auditory experience and phonological processing activities before implantation appears to produce measurable effects on the working memory processes that rely on verbal rehearsal and serial scanning of phonological information in short-term memory.     

Language differences in verbal short-term memory do not exclusively originate in the process of subvocal rehearsal

Language differences in verbal short-term memory were investigated in two experiments. In Experiment 1, bilinguals with high competence in English and French and monolingual English adults with extremely limited knowledge of French were assessed on their serial recall of words and nonwords in both languages. In all cases recall accuracy was superior in the language with which individuals were most familiar, a first-language advantage that remained when variation due to differential rates of articulation in the two languages was taken into account. In Experiment 2, bilinguals recalled lists of English and French words with and without concurrent articulatory suppression. First-language superiority persisted under suppression, suggesting that the language differences in recall accuracy were not attributable to slower rates of subvocal rehearsal in the less familiar language. The findings indicate that language-specific differences in verbal short-term memory do not exclusively originate in the subvocal rehearsal process. It is suggested that one source of language-specific variation might relate to the use of long-term knowledge to support short-term memory performance.     

Do young children rehearse? An individual-differences analysis

The issue of whether young children rehearse in auditory memory tasks was investigated across a series of three studies comparing individual differences in articulation rates and memory spans. Applying the principles of the working-memory model, children with faster rates of speaking should have superior memory spans if they engage in rehearsal. Two of the experiments, with 4-year-old children, failed to establish any significant association between articulation rate and memory span, although both the memory span and articulation rate procedures were found to be highly reliable in this age group A third experiment confirmed that, as expected, articulation rates and memory spans were significantly associated with one another in adult subjects. The results indicate that, contrary to recent theories of children’s short-term-memory development, 4-year-old children do not engage in subvocal rehearsal during auditory memory span tasks.     

Is the superior verbal memory span of Mandarin speakers due to faster rehearsal?

It is well established that digit span in native Chinese speakers is atypically high. This is commonly attributed to a capacity for more rapid subvocal rehearsal for that group. We explored this hypothesis by testing a group of English-speaking native Mandarin speakers on digit span and word span in both Mandarin and English, together with a measure of speed of articulation for each. When compared to the performance of native English speakers, the Mandarin group proved to be superior on both digit and word spans while predictably having lower spans in English. This suggests that the Mandarin advantage is not limited to digits. Speed of rehearsal correlated with span performance across materials. However, this correlation was more pronounced for English speakers than for any of the Chinese measures. Further analysis suggested that speed of rehearsal did not provide an adequate account of differences between Mandarin and English spans or for the advantage of digits over words. Possible alternative explanations are discussed.     

Irrelevant sound disrupts speech production: Exploring the relationship between short-term memory and experimentally induced slips of the tongue

To explore the relationship between short-term memory and speech production, we developed a speech error induction technique. The technique, which was adapted from a Japanese word game, exposed participants to an auditory distractor word immediately before the utterance of a target word. In Experiment 1, the distractor words that were phonologically similar to the target word led to a greater number of errors in speaking the target than did the dissimilar distractor words. Furthermore, the speech error scores were significantly correlated with memory span scores. In Experiment 2, memory span scores were again correlated with the rate of the speech errors that were induced from the task-irrelevant speech sounds. Experiment 3 showed a strong irrelevant-sound effect in the serial recall of nonwords. The magnitude of the irrelevant-sound effects was not affected by phonological similarity between the to-be-remembered nonwords and the irrelevant-sound materials. Analysis of recall errors in Experiment 3 also suggested that there were no essential differences in recall error patterns between the dissimilar and similar irrelevant-sound conditions. Weproposed two different underlying mechanisms in immediate memory, one operating via the phonological short-term memory store and the other via the processes underpinning speech production.     

Think before you speak: pauses, memory search, and trace redintegration processes in verbal memory span

Immediate memory span and speed of memory search were assessed for words and nonwords of short and long spoken duration. Memory span was substantially greater for words than for nonwords and for short than for long items, though speed of memory search was unaffected by either length or lexicality. An analysis of the temporal pattern of responses in the memory span task indicated that inter-item pauses were longer between nonwords than words but that these pause durations were unaffected by item length. A model of verbal short-term memory span is described in which trace selection from a short-term store and the redintegration (restoration) of degraded phonological traces both occur in the pauses between saying successive items. Both trace selection and trace redintegration appear to play important roles in accounting for individual differences in memory span.     

The association between auditory memory span and speech rate in children from kindergarten to sixth grade.

This study reexamined the association between speech rate and memory span in children from kindergarten to sixth grade (N = 152) in order to potentially account for the inconsistencies within the published literature on this topic. Some of the inconsistencies in past research may reflect the different methods adopted in assessing speech rate. In particular, repeating word triples may itself involve memory demands, contaminating the correlation between speech rate and memory span in younger children. Analyses using composite speech rate and memory span measures showed that speech rate for word triples shared variance with memory span that was independent of speech rate for single words. Moreover, speech rate for word triples was largely redundant with age in explaining additional variation in memory span once the effects of speech rate for single words were controlled.     

Determining spatial span: The role of movement time and articulation rate

In studies of verbal memory span individual differences in speech rate have been found to predict the number of items that can be recalled in order. This is thought to happen because overt speech rate is related to the rate of internal verbal rehearsal. For spatial span there may also be an internal rehearsal system linked to overt responding, and if there is a strong analogy to be drawn between the verbal and spatial domains, then movement time between spatial targets should predict the number of spatial locations that can be recalled. In the first study reported, none of the six measures of movement time did predict spatial span, but, as expected, speech rate predicted verbal span. In addition, speech rate predicted spatial span. In a second study the use of articulatory suppression during span presentation showed that verbal span dropped, but was still predicted by speech rate. Spatial span was again predicted by the time it took to say digits rather than the time it took to make movements to spatial targets. There would not seem to be any simple analogy between the limitations on verbal span and those on spatial span. In addition, the relationship between speech rate and sequential memory performance may be more complex than previous studies have suggested.     

Age-related differences in immediate serial recall: Dissociating chunk formation and capacity

We assessed the contribution of two hypothesized mechanisms to impaired memory performance of older adults in an immediate serial recall task: decreased temporary information storage in a capacity-limited mechanism, such as the focus of attention, and a deficit in binding together different components into cohesive chunks. Using a method in which paired associations between words were taught at varying levels to allow an identification of multiword chunks (Cowan, Chen, & Rouder, 2004), we found that older adults recalled considerably fewer chunks and, on average, smaller chunks than did young adults. Their performance was fairly well simulated by dividing attention in younger adults, unlike what has been found for long-term associative learning. Paired-associate knowledge may be used in an implicit manner in serial recall, given that younger adults under divided attention and older adults use it well despite the relatively small chunk capacities displayed by these groups.     

Individual differences in memory span: The contribution of rehearsal, access to lexical memory,and output speed

Rehearsal speed has traditionally been seen to be the prime determinant of individual differences in memory span. Recent studies, in the main using young children as the subject population, have suggested other contributors to span performance, notably contributions from long-term memory and forgetting and retrieval processes occurring during recall. In the current research we explore individual differences in span with respect to measures of rehearsal, output time, and access to lexical memory.We replicate standard short-term phenomena; we show that the variables that influence children's span performance influence adult performance in the same way; and we show that lexical memory access appears to be a more potent source of individual differences in span than either rehearsal speed or output factors.     

<Emphasis Type="Bold">Keeping it together: Semantic coherence stabilizes phonological sequences in short-term memory</Emphasis>

Our ability to hold a sequence of speech sounds in mind, in the correct configuration, supports many aspects of communication, but the contribution of conceptual information to this basic phonological capacity remains controversial. Previous research has shown modest and inconsistent benefits of meaning on phonological stability in short-term memory, but these studies were based on sets of unrelated words. Using a novel design, we examined the immediate recall of sentence-like sequences with coherent meaning, alongside both standard word lists and mixed lists containing words and nonwords. We found, and replicated, substantial effects of coherent meaning on phoneme-level accuracy: The phonemes of both words and nonwords within conceptually coherent sequences were more likely to be produced together and in the correct order. Since nonwords do not exist as items in long-term memory, the semantic enhancement of phoneme-level recall for both item types cannot be explained by a lexically based item reconstruction process employed at the point of retrieval (“redintegration”). Instead, our data show, for naturalistic input, that when meaning emerges from the combination of words, the phonological traces that support language are reinforced by a semantic-binding process that has been largely overlooked by past short-term memory research.     

Short-term implicit memory: Visual, auditory, and cross-modality priming

Short-term implicit memory was examined for mixed auditory (A) and visual (V) stimuli. In lexical decision, words and nonwords were repeated at lags of 0, 1, 3, and 6 intervening trials, in four prime-target combinations (VV, VA, AV, AA). Same-modality repetition priming showed a lag x lexicality interaction for visual stimuli (nonwords decayed faster), but not for auditory stimuli (longer lasting smooth decay for both words and nonwords). These modality differences suggest that short-term priming has a perceptual locus, with the phonological lexicon maintaining stimuli active longer than the orthographic lexicon and treating pseudowords as potential words. We interpret these differences in terms of the different memory needs of speech recognition and text reading. Weak cross-modality short-term priming was present for words and nonwords, indicating recoding between perceptual forms.     

Artificially induced valence of distractor words increases the effects of irrelevant speech on serial recall

In a game context, nonwords either were artificially associated with negative valence or were in some sense neutral or irrelevant. Subsequently, participants memorized target words in silence or while attempting to ignore the negatively valent, irrelevant, or neutral auditory distractor nonwords. The presence of distractor nonwords impaired recall performance, but negative distractor nonwords caused more disruption than neutral and irrelevant distractors, which did not differ in how much disruption they caused. These findings conceptually replicate earlier results showing disruption due to valence with natural language words and extend them by demonstrating that auditory features that may possibly be confounded with valence in natural language words cannot be the cause of the observed disruption. Explanations of the irrelevant speech effect within working memory models that specify an explicit role of attention in the maintenance of information for immediate serial recall can explain this pattern of results, whereas structural models of working memory cannot.     

Age related differences in metacognitive control: role of executive functioning

To examine whether aging affects metacognitive control, elderly and young adults carried out a readiness-recall task, in which subjects monitor their own learning procedure, allowing strategy manipulation (study time and rehearsal) to be measured. Age differences were observed in metamemory control performance. Younger adults were found to be better at adjusting study time and rehearsal to the task. Moreover, to determine whether age-related differences in strategy manipulation may mediate age-related differences in memory performance, performance on the readiness-recall task was compared to performance on an experimenter-paced task. Results indicated that younger adults recalled significantly more words in the readiness-recall task than in the experimenter test. This was not the case for older adults. Furthermore, a hierarchical regression analysis revealed that age-related differences in strategy manipulation mediate some age-related differences in memory performance. Our aim was also to determine whether metacognitive control is related to executive functions. Thus, all participants were administered standard neuropsychological tests used to assess executive functioning. Significant partial correlation appeared between metamemory control and executive functioning. Finally, a hierarchical regression analysis indicated that age-related decline in metamemory control may be largely the result of executive limitations associated with aging.     

Is nonword repetition a test of phonological memory or long-term knowledge? It all depends on the nonwords

The extent to which children's performance on tests of nonword repetition is constrained by phonological working memory and long-term lexical knowledge was investigated in a longitudinal study of 70 children tested at 4 and 5 years of age. At each time of testing, measures of nonword repetition, memory span, and vocabulary knowledge were obtained. Reading ability was also assessed at 5 years. At both ages, repetition accuracy was greater for nonwords of high- rather than low-rated wordlikeness, and memory-span measures were more closely related to repetition accuracy for the low-wordlike than for the high-wordlike stimuli. It is argued that these findings indicate that nonword repetition for unwordlike stimuli is largely dependent on phonological memory, whereas repetition for wordlike items is also mediated by long-term lexical knowledge and is therefore less sensitive to phonological memory constraints. Reading achievement was selectively linked with earlier repetition scores for low-wordlike nonwords, suggesting a phonological memory contribution in the early stages of reading development. Vocabulary knowledge was associated with repetition accuracy for both low- and high-wordlike nonwords, consistent with the notion that lexical knowledge and nonword repetition share a reciprocal developmental relationship.     

The Inner Eye and the Inner Scribe of Visuo-spatial Working Memory: Evidence from Developmental Fractionation

Abstract

Evidence for two major hypotheses that attempt to explain the development in memory span with age is reviewed: the identification time hypothesis and the rehearsal hypothesis. The rehearsal hypothesis is also strongly related to the recent application of the working memory model to memory development. In this model, rehearsal is assumed to occur from an extremely young age. This assumption is critically evaluated. It is concluded that there is no strong support for the identification time hypothesis, except as a facet of familiarity. Neither was there good evidence that very young children use verbal rehearsal, although it did appear to be a factor later on. A revised model is proposed, based on three factors. The first is a speech perception system and phonological store; the second is a speech output system which can be used for sublexical segmentation and later rehearsal. The third system is long-term memory with links to both the speech perception and speech output systems. These links enable active strategies to be developed.     

The development of the use of long-term knowledge to assist short-term recall

The influence of item familiarity upon memory span was examined in adults and children aged 5, 7, and 10 years by comparing the recall of words and nonwords. Using a probed recall task, both item recall and position recall were tested. The effect of familiarity upon item recall was found to develop with age, from no effects in the 5-year-olds to significant effects in the older children and adults. By contrast, no effect of familiarity was found at any age when recall of position was required. Dissociations between word length effects and familiarity effects supported the conclusion that the familiarity effect does not result from rehearsal. Several explanations for the source of the familiarity effect were examined, and the familiarity effect was attributed to a strategic redintegration or reconstruction process, which is necessary for item recall but not for position recall.     

Characteristics of spatial memory span: Is there an analogy to the word length effect, based on movement time?

In studies of verbal short-term memory it has been shown that the length of words to be remembered affects the size of memory span. This word-length effect is attributed to relationships between the rate of rehearsal of verbal material and the time it takes to speak the words being rehearsed. For spatial memory span there may also be an internal rehearsal system linked to overt responding, and if there is a strong analogy to be drawn between the verbal and spatial domains then movement time between spatial targets should predict the number of spatial locations that can be recalled. In the experiments reported here the time taken to move between spatial targets is varied by altering the size of targets and the distance between them. No difference between span performance on a nine-block spatial span task were found, either on immediate recall or on recall after an interval. When recall is of items from an array of 27, grouped in nine sets of three, with only one location in any set being presented on any trial, there is an effect of display size. This effect is consonant with the argument that movement time is related to spatial rehearsal, but other explanations are also possible. However, if recall in this task is scored over the nine sets rather than over the 27 items, then there is no difference between the displays. The results indicate that performance on the normal nine-block spatial-span task cannot be predicted by movement time.