Modality independence of order coding in working memory: Evidence from cross-modal order interference at recall

Working memory researchers do not agree on whether order in serial recall is encoded by dedicated modality-specific systems or by a more general modality-independent system. Although previous research supports the existence of autonomous modality-specific systems, it has been shown that serial recognition memory is prone to cross-modal order interference by concurrent tasks. The present study used a serial recall task, which was performed in a single-task condition and in a dual-task condition with an embedded memory task in the retention interval. The modality of the serial task was either verbal or visuospatial, and the embedded tasks were in the other modality and required either serial or item recall. Care was taken to avoid modality overlaps during presentation and recall. In Experiment 1, visuospatial but not verbal serial recall was more impaired when the embedded task was an order than when it was an item task. Using a more difficult verbal serial recall task, verbal serial recall was also more impaired by another order recall task in Experiment 2. These findings are consistent with the hypothesis of modality-independent order coding. The implications for views on short-term recall and the multicomponent view of working memory are discussed.     

Short-term memory, executive control, and children's route learning

The aim of this study was to investigate route-learning ability in 67 children aged 5 to 11years and to relate route-learning performance to the components of Baddeley's model of working memory. Children carried out tasks that included measures of verbal and visuospatial short-term memory and executive control and also measures of verbal and visuospatial long-term memory; the route-learning task was conducted using a maze in a virtual environment. In contrast to previous research, correlations were found between both visuospatial and verbal memory tasks-the Corsi task, short-term pattern span, digit span, and visuospatial long-term memory-and route-learning performance. However, further analyses indicated that these relationships were mediated by executive control demands that were common to the tasks, with long-term memory explaining additional unique variance in route learning.     

Phonological similarity and lexicality effects in children's verbal short-term memory: Concerns about the interpretation of probed recall data

Probed recall tasks are often used to assess aspects of children's verbal short-term memory development because they are not subject to potentially confounding output effects. However, the marked recency effects that are observed in probed recall means that these tasks are potentially insensitive to experimental manipulations when later serial positions are probed. This clouds the interpretation of data from probed recall studies in which children of different ages are presented with to-be-remembered lists of different lengths. In two experiments we examined the magnitude of phonological similarity and lexicality effects in both 5- to 6- and 8- to 9-year-old children. In each case performance on probed recall tasks was contrasted with that seen on tests of serial recognition. The results indicated that probed recall tasks are potentially less sensitive to experimental manipulations in younger than older children. However, comparable effects of both phonological similarity and lexicality were seen in both age groups using serial recognition procedures. These findings have implications for the interpretation of other studies that have examined the development of verbal short-term memory using probed recall and for theoretical accounts of the development of phonological similarity and lexicality effects in children.     

Phonological similarity and lexicality effects in children's verbal short-term memory: concerns about the interpretation of probed recall data

Probed recall tasks are often used to assess aspects of children's verbal short-term memory development because they are not subject to potentially confounding output effects. However, the marked recency effects that are observed in probed recall means that these tasks are potentially insensitive to experimental manipulations when later serial positions are probed. This clouds the interpretation of data from probed recall studies in which children of different ages are presented with to-be-remembered lists of different lengths. In two experiments we examined the magnitude of phonological similarity and lexicality effects in both 5- to 6- and 8- to 9-year-old children. In each case performance on probed recall tasks was contrasted with that seen on tests of serial recognition. The results indicated that probed recall tasks are potentially less sensitive to experimental manipulations in younger than older children. However, comparable effects of both phonological similarity and lexicality were seen in both age groups using serial recognition procedures. These findings have implications for the interpretation of other studies that have examined the development of verbal short-term memory using probed recall and for theoretical accounts of the development of phonological similarity and lexicality effects in children.     

Working memory, reading, and mathematical skills in children with developmental coordination disorder

The aim of the present study was investigate the relationship between working memory and reading and mathematical skills in 55 children diagnosed with developmental coordination disorder (DCD). The findings indicate a pervasive memory deficit in all memory measures. In particular, deficits observed in visuospatial short-term and working memory tasks were significantly worse than in the verbal short-term memory ones. On the basis of these deficits, the sample was divided into high and low visuospatial memory ability groups. The low visuospatial memory group performed significantly worse on the attainment measures compared to the high visuospatial memory group, even when the contribution of IQ was taken into account. When the sample was divided into high and low verbal working memory ability groups, verbal working memory skills made a unique contribution to attainment only when verbal IQ was taken into account, but not when performance IQ was statistically controlled. It is possible that the processing demands of the working memory tasks together with the active motor component reflected in the visuospatial memory tasks and performance IQ subtest both play a crucial role in learning in children with DCD.     

Hebb learning, verbal short-term memory, and the acquisition of phonological forms in children

Recent work using the Hebb effect as a marker for implicit long-term acquisition of serial order has demonstrated a functional equivalence across verbal and visuospatial short-term memory. The current study extends this observation to a sample of five- to six-year-olds using verbal and spatial immediate serial recall and also correlates the magnitude of Hebb learning with explicit measures of word and nonword paired-associate learning. Comparable Hebb effects were observed in both domains, but only nonword learning was significantly related to the magnitude of Hebb learning. Nonword learning was also independently related to individuals' general level of verbal serial recall. This suggests that vocabulary acquisition depends on both a domain-specific short-term memory system and a domain-general process of learning through repetition.     

Effects of concurrent spatial and verbal memory loads on serial position functions of laterally presented letter strings

In this study the influence of visuospatial and verbal memory loads on the identification of laterally presented letter strings was investigated. In the asymmetry task without concurrent loads, a clear right visual field advantage for letter identification was obtained. Hemisphere-specific effects due to concurrent loads were particularly observed when the difficulty of the load tasks was increased. The effects of visuospatial loads were found to be sex related, suggesting that under heavy load conditions mental rotation selectively overloads the processing capacity of the right hemisphere in males, while in females capacity limitations were observed in both hemispheres. Concurrent visuospatial loads produced more facilitation (or less interference) for letters in the outermost positions of each visual field than for letters in the innermost positions of each visual field. The results of the verbal memory load tasks revealed that an easy verbal load task facilitated performance which was particularly manifest for the right-most letter of both the left visual field and the right visual field. A difficult verbal memory load task interfered with recognition accuracy of letters which was most marked for the center letter in the right visual field. Letter position effects obtained in this study were interpreted in terms of various processing mechanisms influencing the serial position curves.     

A comparison of serial order short-term memory effects across verbal and musical domains

Recent studies suggest that the mechanisms involved in the short-term retention of serial order information may be shared across short-term memory (STM) domains such as verbal and visuospatial STM. Given the intrinsic sequential organization of musical material, the study of STM for musical information may be particularly informative about serial order retention processes and their domain-generality. The present experiment examined serial order STM for verbal and musical sequences in participants with no advanced musical expertise and experienced musicians. Serial order STM for verbal information was assessed via a serial order reconstruction task for digit sequences. In the musical domain, serial order STM was assessed using a novel melodic sequence reconstruction task maximizing the retention of tone order information. We observed that performance for the verbal and musical tasks was characterized by sequence length as well as primacy and recency effects. Serial order errors in both tasks were characterized by similar transposition gradients and ratios of fill-in:infill errors. These effects were observed for both participant groups, although the transposition gradients and ratios of fill-in:infill errors showed additional specificities for musician participants in the musical task. The data support domain-general serial order STM effects but also suggest the existence of additional domain-specific effects. Implications for models of serial order STM in verbal and musical domains are discussed.     

Book Reviews

There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and nondyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuospatial measures of working memory. The results of the visuospatial tasks indicated no between-group differences in static spatial memory, which requires the short-term storage of simultaneously presented information. In almost all conditions there were no between-group differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed nonphonological working memory deficits. In the absence of an explanation involving verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.     

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.     

Visuospatial Short-Term Memory Explains Deficits in Tower Task Planning in High-Functioning Children with Autism Spectrum Disorder

Previous findings on planning abilities in individuals with high-functioning autism spectrum disorder (HFA) are inconsistent. Exploring possible reasons for these mixed findings, the current study investigated the involvement of memory in planning performance in 15 children with HFA and 17 typically developing controls. In addition to planning abilities (measured with the Tower of London), short-term memory and delayed recall for verbal as well as visuospatial material were assessed. Findings suggest that particularly reduced efficiency in visuospatial short-term memory is associated with Tower task planning deficits in children with HFA.     

Effect of perceiving computing to be an acquirable skill upon a computer-mediated serial recall task

Serial recall tasks assess the capacity of verbal short-term memory. The perception of computing as an acquirable skill rather than a fixed ability affected performance upon computer-based serial recall tasks but did not affect performance on comparable pencil-and-paper tasks. Computerized versions of traditional assessments should control for this.     

Direction of Report in Spatial and Verbal Serial Short term Memory

Four experiments examined the role played by item and order information in determining the effects of order of report of a sequence from short-term memory. Experiments in which list items were re-presented prior to recall so that only their order had to be reported showed no differences in performance between the forward and backward direction of report. This result was found with lists of auditory-verbal, visual-verbal, and spatial stimuli. When the list items were not re-presented, so that recall of both items and order was required, recall in the backward direction of report was significantly worse than in the forward direction of report, both in spatial and verbal tasks. The results point to the symmetry of inter-item associations, though only equivocally so, but they suggest strongly that the processes of spatial and verbal serial recall share many functional characteristics.     

Response selection involves executive control: Evidence from the selective interference paradigm

In the present study, we investigated whether response selection involves executive control, using the selective interference paradigm within Baddeley's (1986) working memory framework. The interference from response selection was estimated by comparing the patterns of dual-task interference of simple and choice RT tasks with those of a number of established working memory tasks. In Experiment 1, we compared impairment of forward and backward verbal serial recall from the RT tasks and articulatory suppression. Experiment 2 measured the adverse effects of the RT tasks and matrix tapping on forward and backward visuospatial serial recall. Finally, in Experiment 3, we examined the impairment from the RT tasks with two measures of executive control--namely, letter and category fluency. Altogether, the three experiments demonstrated that response selection interferes with executive control and that the interference is not produced at the level of working memory's slave systems, which supports the assumption of executive involvement in response selection.     

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.     

Revisiting evidence for modularity and functional equivalence across verbal and spatial domains in memory

The authors revisited evidence in favor of modularity and of functional equivalence between the processing of verbal and spatial information in short-term memory. This was done by investigating the patterns of intrusions, omissions, transpositions, and fill-ins in verbal and spatial serial recall and order reconstruction tasks under control, articulatory suppression, and spatial tapping conditions. The authors observed that when tasks were fully equated, all patterns of errors were equivalent between the verbal and spatial domains. Moreover, articulatory suppression interfered more with the verbal memory tasks than with the spatial memory tasks. This interference was mostly due to an increase of omissions and transpositions. Similarly, tapping was more disruptive of spatial memory than of verbal memory tasks and affected primarily the number of omissions and transpositions. The patterns of errors and their interaction with interference are discussed in light of the predominant approaches to modeling memory and provide a rich set of data for modeling efforts.     

Evidence for modality-independent order coding in working memory

The aim of the present study was to investigate the representation of serial order in working memory, more specifically whether serial order is coded by means of a modality-dependent or a modality-independent order code. This was investigated by means of a series of four experiments based on a dual-task methodology in which one short-term memory task was embedded between the presentation and recall of another short-term memory task. Two aspects were varied in these memory tasks—namely, the modality of the stimulus materials (verbal or visuo-spatial) and the presence of an order component in the task (an order or an item memory task). The results of this study showed impaired primary-task recognition performance when both the primary and the embedded task included an order component, irrespective of the modality of the stimulus materials. If one or both of the tasks did not contain an order component, less interference was found. The results of this study support the existence of a modality-independent order code.     

Exploring the characteristics of the visuospatial hebb repetition effect

Using the dot task (see Jones, Farrand, Stuart, & Morris, 1995)--regarded as a good visuospatial analogue of the verbal serial recall task--we examined whether the Hebb repetition effect and its characteristics can be extended to visuospatial material. Classically, the Hebb effect has been associated with serial verbal memory: Repetition of a to-be-remembered sequence of verbal items every third trial markedly improves serial recall of that sequence. In the present study, Hebb effects were observed with visuospatial information, and a direct comparison between verbal and spatialsequence learning revealed that the Hebb repetition effect for visuospatial information shares similar characteristics with its verbal analogue. Our results cast some doubt regarding the parsimony of the view that the classical verbal Hebb effect is driven by a store specialized for phonological information and impose some further constraints on modeling serial memory and implicit sequence learning.     

Serial recall of rhythms and verbal sequences: Impacts of concurrent tasks and irrelevant sound

Rhythmic grouping enhances verbal serial recall, yet very little is known about memory for rhythmic patterns. The aim of this study was to compare the cognitive processes supporting memory for rhythmic and verbal sequences using a range of concurrent tasks and irrelevant sounds. In Experiment 1, both concurrent articulation and paced finger tapping during presentation and during a retention interval impaired rhythm recall, while letter recall was only impaired by concurrent articulation. In Experiments 2 and 3, irrelevant sound consisted of irrelevant speech or tones, changing-state or steady-state sound, and syncopated or paced sound during presentation and during a retention interval. Irrelevant speech was more damaging to rhythm and letter recall than was irrelevant tone sound, but there was no effect of changing state on rhythm recall, while letter recall accuracy was disrupted by changing-state sound. Pacing of sound did not consistently affect either rhythm or letter recall. There are similarities in the way speech and rhythms are processed that appear to extend beyond reliance on temporal coding mechanisms involved in serial-order recall.     

Serial recall of rhythms and verbal sequences: Impacts of concurrent tasks and irrelevant sound

Rhythmic grouping enhances verbal serial recall, yet very little is known about memory for rhythmic patterns. The aim of this study was to compare the cognitive processes supporting memory for rhythmic and verbal sequences using a range of concurrent tasks and irrelevant sounds. In Experiment 1, both concurrent articulation and paced finger tapping during presentation and during a retention interval impaired rhythm recall, while letter recall was only impaired by concurrent articulation. In Experiments 2 and 3, irrelevant sound consisted of irrelevant speech or tones, changing-state or steady-state sound, and syncopated or paced sound during presentation and during a retention interval. Irrelevant speech was more damaging to rhythm and letter recall than was irrelevant tone sound, but there was no effect of changing state on rhythm recall, while letter recall accuracy was disrupted by changing-state sound. Pacing of sound did not consistently affect either rhythm or letter recall. There are similarities in the way speech and rhythms are processed that appear to extend beyond reliance on temporal coding mechanisms involved in serial-order recall.