Short-term memory stages in sign vs. speech: the source of the serial span discrepancy

Speakers generally outperform signers when asked to recall a list of unrelated verbal items. This phenomenon is well established, but its source has remained unclear. In this study, we evaluate the relative contribution of the three main processing stages of short-term memory – perception, encoding, and recall – in this effect. The present study factorially manipulates whether American Sign Language (ASL) or English is used for perception, memory encoding, and recall in hearing ASL-English bilinguals. Results indicate that using ASL during both perception and encoding contributes to the serial span discrepancy. Interestingly, performing recall in ASL slightly increased span, ruling out the view that signing is in general a poor choice for short-term memory. These results suggest that despite the general equivalence of sign and speech in other memory domains, speech-based representations are better suited for the specific task of perception and memory encoding of a series of unrelated verbal items in serial order through the phonological loop. This work suggests that interpretation of performance on serial recall tasks in English may not translate straightforwardly to serial tasks in sign language.     

How grammar can cope with limited short-term memory: simultaneity and seriality in sign languages

It is known that in American Sign Language (ASL) span is shorter than in English, but this discrepancy has never been systematically investigated using other pairs of signed and spoken languages. This finding is at odds with results showing that short-term memory (STM) for signs has an internal organization similar to STM for words. Moreover, some methodological questions remain open. Thus, we measured span of deaf and matched hearing participants for Italian Sign Language (LIS) and Italian, respectively, controlling for all the possible variables that might be responsible for the discrepancy: yet, a difference in span between deaf signers and hearing speakers was found. However, the advantage of hearing subjects was removed in a visuo-spatial STM task. We attribute the source of the lower span to the internal structure of signs: indeed, unlike English (or Italian) words, signs contain both simultaneous and sequential components. Nonetheless, sign languages are fully-fledged grammatical systems, probably because the overall architecture of the grammar of signed languages reduces the STM load. Our hypothesis is that the faculty of language is dependent on STM, being however flexible enough to develop even in a relatively hostile environment.     

Relations between vocabulary development and verbal short-term memory: The relative importance of short-term memory for serial order and item information

Although many studies have shown an association between verbal short-term memory (STM) and vocabulary development, the precise nature of this association is not yet clear. The current study reexamined this relation in 4- to 6-year-olds by designing verbal STM tasks that maximized memory for either item or serial order information. Although empirical data suggest that distinct STM processes determine item and serial order recall, these were generally confounded in previous developmental studies. We observed that item and order memory tasks were independently related to vocabulary development. Furthermore, vocabulary development was more strongly associated with STM for order information in 4- and 6-year-olds and with STM for item information in 5-year-olds. These data highlight the specificity of verbal STM for serial order and item information and suggest a causal association between order STM processes and vocabulary development, at least in 4- and 6-year-olds.     

Midazolam amnesia and short-term/working memory processes

We examined whether midazolam impairs short-term/working memory processes. We hypothesize that prior dissociations in midazolam's effects on short-term/working memory tasks and episodic memory tasks arise because midazolam has a larger effect on episodic memory processes than on short-term/working memory processes. To examine these issues, .03 mg/kg of participant's bodyweight of midazolam was administered in a double-blind placebo-controlled within-participant design. Performance on the digit span and category generation/recall tasks was examined. The results of Experiment 1 demonstrated that: (1) midazolam impaired performance on the digit span task; (2) midazolam did not impair performance on the category generation task; (3) midazolam impaired performance on the category recall task; and (4) midazolam's effect on category recall was four times as large as its effect on digit span. The results of Experiment 2 demonstrated that midazolam did not impair digit span performance when the digit span task was administered at a later time. These results suggest that midazolam can impair short-term/working memory processes, but these effects are substantially smaller than midazolam's effect on episodic memory processes. Moreover, they demonstrate that conscious awareness of materials during study is not sufficient to produce episodic memory.     

The real relationship between short-term memory and working memory

Storage-oriented memory span tasks with no explicit concurrent processing are usually referred as short-term memory (STM) tasks, whereas tasks involving storage plus concurrent processing requirements are designated as working memory (WM) tasks. The present study explores a question that remains unsolved: Do STM and WM tasks clearly tap distinguishable theoretical constructs? For that purpose, a large sample of 403 participants was tested through 12 diverse memory span tasks. Half of those tasks are widely accepted as measures of STM, whereas the other half measure WM. The results show that STM and WM share largely overlapping underlying capacity limitations, suggesting that all memory span tasks tap essentially the same construct. Some implications are discussed.     

The real relationship between short-term memory and working memory

Storage-oriented memory span tasks with no explicit concurrent processing are usually referred as short-term memory (STM) tasks, whereas tasks involving storage plus concurrent processing requirements are designated as working memory (WM) tasks. The present study explores a question that remains unsolved: Do STM and WM tasks clearly tap distinguishable theoretical constructs? For that purpose, a large sample of 403 participants was tested through 12 diverse memory span tasks. Half of those tasks are widely accepted as measures of STM, whereas the other half measure WM. The results show that STM and WM share largely overlapping underlying capacity limitations, suggesting that all memory span tasks tap essentially the same construct. Some implications are discussed.     

Working memory and vocabulary development in Greek preschool and primary school children

The present research investigated the relative contributions of verbal short-term memory (STM) and working memory (WM) to vocabulary development in the early years among Greek-speaking children. Participants were 5.5-, 7.5-, 8.5- and 9.5-year-old (N = 216) native speakers of Greek, a language differing from English in which most investigations have been conducted. Children were assessed with a receptive vocabulary task, four verbal STM measures (word, digit, and non-word list recall, as well as word list matching), and three verbal WM tasks (listening, counting, and backward digit recall). Results offer support to the view that both STM and WM influence vocabulary development in early stages. Vocabulary was associated with verbal STM at 7.5 and 8.5 years, but only with verbal WM at 5.5 years. Associations declined with age (by 9.5 years), earlier than in English-speaking children. Findings are discussed in relation to Greek language characteristics, demonstrating the importance of cross-cultural investigations.     

Contribution of lexico-semantic processes to verbal short-term memory tasks: a PET activation study

Recent studies have demonstrated the intervention of long-term memory processes in verbal STM tasks and several cognitive models have been proposed to explain these effects. A PET study was performed in order to determine whether supplementary cerebral areas are involved when subjects have to execute short-term memory tasks for items having representations in long-term memory (in comparison to items without such representations: words vs non-words). Results indicate that verbal STM for words specifically involves the left middle temporal gyrus (BA 21) and temporo-parietal junction (BA 39). These areas can be associated with lexical and semantic processes. These results are in agreement with cognitive models that postulate the simultaneous influence of lexical and semantic long-term representations on verbal STM processes and/or a lexico-semantic buffer.     

Temporal grouping effects in musical short-term memory

Recent theoretical accounts of verbal and visuo-spatial short-term memory (STM) have proposed the existence of domain-general mechanisms for the maintenance of serial order information. These accounts are based on the observation of similar behavioural effects across several modalities, such as temporal grouping effects. Across two experiments, the present study aimed at extending these findings, by exploring a STM modality that has received little interest so far, STM for musical information. Given its inherent rhythmic, temporal and serial organisation, the musical domain is of interest for investigating serial order STM processes such as temporal grouping. In Experiment 1, the data did not allow to determine the presence or the absence of temporal grouping effects. In Experiment 2, we observed that temporal grouping of tone sequences during encoding improves short-term recognition for serially presented probe tones. Furthermore, the serial position curves included micro-primacy and micro-recency effects, which are the hallmark characteristic of temporal grouping. Our results suggest that the encoding of serial order information in musical STM may be supported by temporal positional coding mechanisms similar to those reported in the verbal domain.     

The relationship between language production and verbal short-term memory: The role of stress grouping

This study investigates the influence of stress grouping on verbal short-term memory (STM). English speakers show a preference to combine syllables into trochaic groups, both lexically and in continuous speech. In two serial recall experiments, auditory lists of nonsense syllables were presented with either trochaic (STRONG–weak) or iambic (weak–STRONG) stress patterns, or in monotone. The acoustic correlates that carry stress were also manipulated in order to examine the relationship between input and output processes during recall. In Experiment 1, stressed and unstressed syllables differed in intensity and pitch but were matched for spoken duration. Significantly more syllables were recalled in the trochaic stress pattern condition than in the iambic and monotone conditions, which did not differ. In Experiment 2, spoken duration and pitch were manipulated but intensity was held constant. No effects of stress grouping were observed, suggesting that intensity is a critical acoustic factor for trochaic grouping. Acoustic analyses demonstrated that speech output was not identical to the auditory input, but that participants generated correct stress patterns by manipulating acoustic correlates in the same way in both experiments. These data challenge the idea of a language-independent STM store and support the notion of separable phonological input and output processes.     

Long-term associative learning predicts verbal short-term memory performance

Studies using tests such as digit span and nonword repetition have implicated short-term memory across a range of developmental domains. Such tests ostensibly assess specialized processes for the short-term manipulation and maintenance of information that are often argued to enable long-term learning. However, there is considerable evidence for an influence of long-term linguistic learning on performance in short-term memory tasks that brings into question the role of a specialized short-term memory system separate from long-term knowledge. Using natural language corpora, we show experimentally and computationally that performance on three widely used measures of short-term memory (digit span, nonword repetition, and sentence recall) can be predicted from simple associative learning operating on the linguistic environment to which a typical child may have been exposed. The findings support the broad view that short-term verbal memory performance reflects the application of long-term language knowledge to the experimental setting.     

语音短时记忆与词汇知识对第二语言词汇学习的影响

选取两种语音熟悉程度不同的非词为实验材料,把语音短时记忆区分为项目短时记忆和序列短时记忆,考察语音短时记忆与词汇知识对汉英双语者第二语言（英语）词汇学习的影响。实验1采用产出性的方式进行学习,结果发现,词汇知识与项目短时记忆对语音熟悉非词的学习起预测作用;词汇知识与序列短时记忆对语音不熟悉非词学习起预测作用。实验2采用接受性的方式进行学习,结果发现,项目短时记忆、序列短时记忆和词汇知识都对语音熟悉非词学习起独立的预测作用;项目短时记忆和序列短时记忆对语音不熟悉非词学习起独立的预测作用。实验结果表明,语音短时记忆和词汇知识都是影响英语词汇学习的重要因素。具体而言,学习语音熟悉的词汇,词汇知识起着更为重要的作用;学习语音不熟悉的词汇,语音短时记忆、特别是序列短时记忆起着更为重要的作用,而且两者作用的大小随着词汇学习方式的不同而发生变化。     

Exploring the relationship between new word learning and short-term memory for serial order recall,item recall,and item recognition

We reexplored the relationship between new word learning and verbal short-term memory (STM) capacities, by distinguishing STM for serial order information, item recall, and item recognition. STM capacities for order information were estimated via a serial order reconstruction task. A rhyme probe recognition task assessed STM for item recognition. Item recall capacities were derived from the proportion of item errors in an immediate serial recall task. In Experiment 1, strong correlations were observed between item recall and item recognition, but not between the item STM tasks and the serial order task, supporting recent theoretical positions that consider that STM for item and serial order rely on distinct capacities. Experiment 2 showed that only the serial order reconstruction task predicted independent variance in a paired associate word–nonword learning task. Our results suggest that STM capacities for serial order play a specific and causal role in learning new phonological information.     

The effects of word co-occurrence on short-term memory: associative links in long-term memory affect short-term memory performance

In immediate serial recall tasks, high-frequency words are recalled better than low-frequency words. This has been attributed to high-frequency words' being better represented and providing more effective support to a redintegration process at retrieval (C. Hulme et al., 1997). In studies of free recall, there is evidence that frequency of word co-occurrence, rather than word frequency per se, may explain the recall advantage enjoyed by high-frequency words (J. Deese, 1960). The authors present evidence that preexposing pairs of low-frequency words, so as to create associative links between them, has substantial beneficial effects on immediate serial recall performance. These benefits, which are not attributable to simple familiarization with the words per se, do not occur for high-frequency words. These findings indicate that associative links between items in long-term memory have important effects on short-term memory performance and suggest that the effects of word frequency in short-term memory tasks are related to differences in interitem associations in long-term memory.     

Short-term memory and working memory as indices of children's cognitive skills

In the current literature, empirical and conceptual distinctions have been drawn between a more or less passive short-term memory (STM) system and a more dynamic working memory (WM) system. Distinct tasks have been developed to measure their capacity and research has generally shown that, for adults, WM, and not STM, is a reliable predictor of general cognitive ability. However, the locus of the differences between the tasks has received little attention. We present data from children concerning measures of matrices reasoning ability, reading, and numerical skill along with forward and backward order serial recall of WM, STM, and STM with articulatory suppression tasks. As indices of children's cognitive skills, STM and WM are shown to be rather similar in terms of memory per se. Neither the opportunity for rehearsal nor task complexity provides satisfactory explanations for differences between memory tests.     

Dissociations of the number and precision of visual short-term memory representations in change detection

The present study dissociated the number (i.e., quantity) and precision (i.e., quality) of visual short-term memory (STM) representations in change detection using receiver operating characteristic (ROC) and experimental manipulations. Across three experiments, participants performed both recognition and recall tests of visual STM using the change-detection task and the continuous color-wheel recall task, respectively. Experiment 1 demonstrated that the estimates of the number and precision of visual STM representations based on the ROC model of change-detection performance were robustly correlated with the corresponding estimates based on the mixture model of continuous-recall performance. Experiments 2 and 3 showed that the experimental manipulation of mnemonic precision using white-noise masking and the experimental manipulation of the number of encoded STM representations using consolidation masking produced selective effects on the corresponding measures of mnemonic precision and the number of encoded STM representations, respectively, in both change-detection and continuous-recall tasks. Altogether, using the individual-differences (Experiment 1) and experimental dissociation (Experiment 2 and 3) approaches, the present study demonstrated the some-or-none nature of visual STM representations across recall and recognition.     

Short-term memory and working memory as indices of children's cognitive skills

In the current literature, empirical and conceptual distinctions have been drawn between a more or less passive short-term memory (STM) system and a more dynamic working memory (WM) system. Distinct tasks have been developed to measure their capacity and research has generally shown that, for adults, WM, and not STM, is a reliable predictor of general cognitive ability. However, the locus of the differences between the tasks has received little attention. We present data from children concerning measures of matrices reasoning ability, reading, and numerical skill along with forward and backward order serial recall of WM, STM, and STM with articulatory suppression tasks. As indices of children's cognitive skills, STM and WM are shown to be rather similar in terms of memory per se. Neither the opportunity for rehearsal nor task complexity provides satisfactory explanations for differences between memory tests.     

Context in verbal short-term memory

We tested the hypothesis that stimulus-related contextual information that is incidental to task demands-an episodic code-is automatically, obligatorily encoded and stored as a part of short-term memory (STM) representations. Four experiments employed a running span task to investigate the effects of manipulating two types of contextual information: stimulus grouping and color. Three experiments established that grouping context effects are sensitive neither to volitional control nor to task difficulty and that they generalize across testing procedures (yes/no recognition and immediate serial recall). A fourth experiment demonstrated an effect of manipulating the congruity of the color of stimuli between study and test. These demonstrations of the robustness and generality of context effects in STM are consistent with the predictions of the episodic coding model of STM.     

Impact of auditory selective attention on verbal short-term memory and vocabulary development

This study investigated the role of auditory selective attention capacities as a possible mediator of the well-established association between verbal short-term memory (STM) and vocabulary development. A total of 47 6- and 7-year-olds were administered verbal immediate serial recall and auditory attention tasks. Both task types probed processing of item and serial order information because recent studies have shown this distinction to be critical when exploring relations between STM and lexical development. Multiple regression and variance partitioning analyses highlighted two variables as determinants of vocabulary development: (a) a serial order processing variable shared by STM order recall and a selective attention task for sequence information and (b) an attentional variable shared by selective attention measures targeting item or sequence information. The current study highlights the need for integrative STM models, accounting for conjoined influences of attentional capacities and serial order processing capacities on STM performance and the establishment of the lexical language network.     

Short-term recall by deaf signers of American Sign Language: implications of encoding strategy for order recall

Two experiments were conducted on short-term recall of printed English words by deaf signers of American Sign Language (ASL). Compared with hearing subjects, deaf subjects recalled significantly fewer words when ordered recall of words was required, but not when free recall was required. Deaf subjects tended to use a speech-based code in probed recall for order, and the greater the reliance on a speech-based code, the more accurate the recall. These results are consistent with the hypothesis that a speech-based code facilitates the retention of order information.