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.     

Recognition memory for tactile sequences.

In three experiments participants were required to compare the similarity in item order for two temporally separated sequences of tactile stimuli presented to the fingers of the hand. Between-sequence articulatory suppression but not tactile interference impaired recognition accuracy (Experiment 1), and the null effect of tactile interference was not due to the second tactile sequence overwriting the sensory record of the first sequence (Experiment 2). Experiment 3 showed that compared to a condition where the second sequence was presented in the tactile modality only, recognition was enhanced when the second sequence was seen presented either to the hand or on a diagrammatic representation of a hand. A final experiment showed that the effects of Experiment 1 were replicated when the underside of the forearm was used for stimulus presentation, suggesting that the data are not idiosyncratic to the first method of presentation. The pattern of results suggests memory for a sequence of tactile stimuli involves the deployment of strategies utilising a combination of verbal rehearsal and visuo-spatial recoding rather than relying solely on the retention of sensory traces. This is taken to reflect limitations in both the capacity and duration of tactile sensory memory.     

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.     

The contribution of short-term memory for serial order to early reading acquisition: evidence from a longitudinal study

Early reading acquisition skills have been linked to verbal short-term memory (STM) capacity. However, the nature of this relationship remains controversial because verbal STM, like reading acquisition, depends on the complexity of underlying phonological processing skills. This longitudinal study addressed the relation between STM and reading decoding acquisition by distinguishing between STM for item information and STM for order information based on recent studies showing that STM for item information, but not STM for order information, recruits underlying phonological representations. If there is a specific link between STM and reading decoding acquisition, STM for order information should be an independent predictor of reading decoding acquisition. Tasks maximizing STM for serial order or item information, measures of phonological abilities, and reading tests were administered to children followed from kindergarten through first grade. We observed that order STM capacity, but not item STM capacity, predicted independent variance in reading decoding abilities 1 year later. These results highlight the specific role of STM for order in reading decoding acquisition and argue for a causal role of order STM capacity in reading acquisition. Mechanisms relating STM for order information and reading acquisition are discussed.     

Verbal recoding of visual stimuli impairs mentalimagetransformations

Two experiments were carried out to test the hypothesis that verbal recoding of visual stimuli in short-term memory influences long-term memory encoding and impairs subsequent mental image operations. Easy and difficult-to-name stimuli were used. When rotated 90 degrees counterclockwise, each stimulus revealed a new pattern consisting of two capital letters joined together. In both experiments, subjects first learned a short series of stimuli and were then asked to rotate mental images of the stimuli in order to detect the hidden letters. In Experiment 1, articulatory suppression was used to prevent subjects from subvocal rehearsal when learning the stimuli, whereas in Experiment 2, verbal labels were presented with each stimulus during learning to encourage a reliance on the verbal code. As predicted, performance in the imagery task was significantly improved by suppression when the stimuli were easy to name (Experiment 1) but was severely disrupted by labeling when the stimuli were difficult to name (Experiment 2). We concluded that verbal recoding of stimuli in short-term memory during learning disrupts the ability to generate veridical mental images from long-term memory.     

The role of articulatory suppression in immediate false recognition

False memory for critical lures has been widely documented in long-term memory using the Deese/Roediger-McDermott paradigm. Recent evidence suggests that false memory effects can also be found in short-term memory (STM), supporting models that assume a strong relationship between short-term and long-term memory processes. However, no study has examined the role of articulatory suppression on immediate false memory, even though phono-articulatory factors are critically involved in STM performance and are an intrinsic part of all STM accounts. The current study proposes a novel paradigm to assess false memory effects in a STM task under both silent and articulatory suppression conditions. Using immediate serial recognition, in which participants had to judge whether two successive mixed lists of six associated and non-associated words were matched, we examined true recognition of matching lists and false recognition of mismatching lists comprising a critical lure or unrelated distractor in two experiments. Results from both experiments indicated reduced true recognition of matching lists and greater false serial recognition of mismatching lists comprising a critical lure under articulatory suppression relative to silence. These findings provide further support for some current models of verbal short-term memory, which posit a strong relationship between short-term and long-term memory processes.     

Modality Effects and the Development of the Word Length Effect in Children

Two experiments investigated the development of the word length effect in children aged 4 to 10 years, comparing auditory and visual stimuli. The question addressed was whether word length effects emerged earlier with auditory presentation or visual presentation, or whether they emerged at the same age regardless of presentation modality. Results provided evidence that word length effects emerge earlier with visual than auditory presentation. The implication of our results is that with visual presentation, 4-year-olds engage in some form of verbalisation strategy that involves obtaining phonological representations of picture names and mapping them on to articulatory output plans. This strategy is clearly verbal in nature, but is not necessarily characterised as cumulative verbal rehearsal.     

Stimulus modality and working memory performance in Greek children with reading disabilities: Additional evidence for the pictorial superiority hypothesis

This study investigated the effects of stimulus presentation modality on working memory performance in children with reading disabilities (RD) and in typically developing children (TDC), all native speakers of Greek. It was hypothesized that the visual presentation of common objects would result in improved learning and recall performance as compared to the auditory presentation of stimuli. Twenty children, ages 10–12, diagnosed with RD were matched to 20 TDC age peers. The experimental tasks implemented a multitrial verbal learning paradigm incorporating three modalities: auditory, visual, and auditory plus visual. Significant group differences were noted on language, verbal and nonverbal memory, and measures of executive abilities. A mixed-model MANOVA indicated that children with RD had a slower learning curve and recalled fewer words than TDC across experimental modalities. Both groups of participants benefited from the visual presentation of objects; however, children with RD showed the greatest gains during this condition. In conclusion, working memory for common verbal items is impaired in children with RD; however, performance can be facilitated, and learning efficiency maximized, when information is presented visually. The results provide further evidence for the pictorial superiority hypothesis and the theory that pictorial presentation of verbal stimuli is adequate for dual coding.     

Selective interference with verbal short-term memory for serial order information: A new paradigm and tests of a timing-signal hypothesis

Many recent computational models of verbal short-term memory postulate a separation between processes supporting memory for the identity of items and processes supporting memory for their serial order. Furthermore, some of these models assume that memory for serial order is supported by a timing signal. We report an attempt to find evidence for such a timing signal by comparing an “item probe” task, requiring memory for items, with a “list probe” task, requiring memory for serial order. Four experiments investigated effects of irrelevant speech, articulatory suppression, temporal grouping, and paced finger tapping on these two tasks. In Experiments 1 and 2, irrelevant speech and articulatory suppression had a greater detrimental effect on the list probe task than on the item probe task. Reaction time data indicated that the list probe task, but not the item probe task, induced serial rehearsal of items. Phonological similarity effects confirmed that both probe tasks induced phonological recoding of visual inputs. Experiment 3 showed that temporal grouping of items during list presentation improved performance on the list probe task more than on the item probe task. In Experiment 4, paced tapping had a greater detrimental effect on the list probe task than on the item probe task. However, there was no differential effect of whether tapping was to a simple or a complex rhythm. Overall, the data illustrate the utility of the item probe/list probe paradigm and provide support for models that assume memory for serial order and memory for items involve separate processes. Results are generally consistent with the timing-signal hypothesis but suggest further factors that need to be explored to distinguish it from other accounts.     

Dynamic relationships between phonological memory and reading: A five year longitudinal study from age 4 to 9

We reconcile competing theories of the role of phonological memory in reading development, by uncovering their dynamic relationship during the first 5 years of school. Phonological memory, reading and phoneme awareness were assessed in 780 phonics‐educated children at age 4, 5, 6 and 9. Confirmatory factor analyses demonstrated that phonological memory loaded onto two factors: verbal short‐term memory (verbal STM; phonological tasks that loaded primarily on serial order memory) and nonword repetition. Using longitudinal structural equation models, we found that verbal STM directly predicted early word‐level reading from age 4 to 6, reflecting the importance of serial‐order memory for letter‐by‐letter decoding. In contrast, reading had no reciprocal influence on the development of verbal STM. The relationship between nonword repetition and reading was bidirectional across the 5 years of study: nonword repetition and reading predicted each other both directly and indirectly (via phoneme awareness). Indirect effects from nonword repetition (and verbal STM) to reading support the view that phonological memory stimulates phonemically detailed representations through repeated encoding of complex verbal stimuli. Similarly, the indirect influence of reading on nonword repetition suggests that improved reading ability promotes the phoneme‐level specificity of phonological representations. Finally, the direct influence from reading to nonword repetition suggests that better readers use orthographic cues to help them remember and repeat new words accurately. A video abstract of this article can be viewed at https://www.youtube.com/watch?v=70LZfTR0BjE .     

Verbal coding and the storage of form-position associations in visual-spatial short-term memory

Short-term memory for form-position associations was assessed using an object relocation task. Participants attempted to remember the positions of either three or five Japanese Kanji characters, presented on a computer monitor. Following a short blank interval, participants were presented with 2 alternative Kanji, only 1 of which was present in the initial stimulus, and the set of locations occupied in the initial stimulus. They attempted to select the correct item and relocate it back to its original position. The proportion of correct item selections showed effects of both articulatory suppression and memory load. In contrast, the conditional probability of location given a correct item selection showed an effect of load but no effect of suppression. These results are consistent with the proposal that access to visual memory is aided by verbal recoding, but that there is no verbal contribution to memory for the association between form and position.     

Paired associate learning in Chinese children with dyslexia

A total of 82 Chinese 11- and 12-year-olds with and without dyslexia were tested on four paired associate learning (PAL) tasks, phonological awareness, morphological awareness, rapid naming, and verbal short-term memory in three different experiments. Experiment 1 demonstrated that children with dyslexia were significantly poorer in visual-verbal PAL than nondyslexic children but that these groups did not differ in visual-visual PAL performance. In Experiment 2, children with dyslexia had more difficulties in transferring rules to new stimuli in a rule-based visual-verbal PAL task as compared with children without dyslexia. Long-term retention of PAL was not impaired in dyslexic children across either experiment. In Experiment 3, rates of visual-verbal PAL deficits among children with dyslexia were all at or above 39%, the highest among all cognitive deficits tested. Moreover, rule-based visual-verbal PAL, in addition to morphological awareness and rapid naming ability, uniquely distinguished children with and without dyslexia even with other metalinguistic skills statistically controlled. Results underscore the importance of visual-verbal PAL for understanding reading impairment in Chinese children.     

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.     

双重缺陷汉语发展性阅读障碍儿童的言语工作记忆和阅读能力研究

选取语音意识和快速自动命名双重缺陷的汉语发展性阅读障碍儿童,探讨其言语工作记忆和阅读能力的发展特点。实验选取双重缺陷的发展性阅读障碍（DD）、年龄匹配（CA）和能力匹配（RL）三组儿童各25名,要求他们完成言语工作记忆（数字广度、汉字广度）和阅读（一分钟词汇阅读、三分钟句子阅读）任务。结果发现,DD儿童的数字倒背位数、一分钟读词数、三分钟读过字数和句子理解正确率均显著低于CA儿童,而与RL儿童差异不显著;DD儿童的句子阅读正确率显著低于CA、RL儿童。表明双重缺陷DD儿童在言语工作记忆和阅读能力上存在一定程度的发展滞后和缺陷。     

Dyslexia: the articulatory hypothesis revisited

Articulatory disorders have been associated with developmental phonological dyslexia in the literature. However, very few information is available about the articulatory movements involved in speech production in dyslexic children. This study uses aerodynamic/acoustic data to explore how dyslexic children produce bilabial stops in French (/b, p/) within a sentence where they occurred in two positions and in three vowel environments. Average durations of articulatory closure and release were calculated in 10 phonological dyslexic children and two groups of age-matched and reading age-matched controls. Moreover, deviation from a standard pronunciation of the same material was evaluated separately by blind examiners. Our results reveal differences in the timing of the articulatory movements between dyslexics and normal controls, as well as more deviations from the target consonant for the dyslexics than for the controls. These observations are consistent with recent findings pointing to a general deficit in fine motor control in dyslexia.     

Tactile Short-term Memory Revisited

In spite of a large body of empirical research demonstrating the importance of multisensory integration in cognition, there is still little research about multimodal encoding and maintenance effects in working memory. In this study we investigated multimodal encoding in working memory by means of an immediate serial recall task with different modality and format conditions. In a first non-verbal condition participants were presented with sequences of non-verbal inputs representing familiar (concrete) objects, either in visual, auditory or audio-visual formats. In a second verbal condition participants were presented with written, spoken, or bimodally presented words denoting the same objects represented by pictures or sounds in the non-verbal condition. The effects of articulatory suppression were assessed in both conditions. We found a bimodal superiority effect on memory span with non-verbal material, and a larger span with auditory (or bimodal) versus visual presentation with verbal material, with a significant effect of articulatory suppression in the two conditions.     

Working memory functioning in developmental dyslexia

Working memory impairments in dyslexia are well documented. However, research has mostly been limited to the phonological domain, a modality in which people with dyslexia have a range of problems. In this paper, 22 adult students with dyslexia and 22 age- and IQ-matched controls were presented with both verbal and visuospatial working memory tasks. Performance was compared on measures of simple span, complex span (requiring both storage and processing), and dynamic memory updating in the two domains. The dyslexic group had significantly lower spans than the controls on all the verbal tasks, both simple and complex, and also on the spatial complex span measure. Impairments remained on the complex span measures after controlling statistically for simple span performance, suggesting a central executive impairment in dyslexia. The novelty of task demands on the initial trials of the spatial updating task also proved more problematic for the dyslexic than control participants. The results are interpreted in terms of extant theories of dyslexia. The possibility of a supervisory attentional system deficit in dyslexia is also raised. It seems clear that working memory difficulties in dyslexia extend into adulthood, can affect performance in both the phonological and visuospatial modalities, and implicate central executive dysfunction, in addition to problems with storage.