Effects of word frequency and age of acquisition on short-term memory span

Differential linguistic features of verbal fluency in behavioral variant frontotemporal dementia and primary progressive aphasia

Frontotemporal dementia (FTD) is an early-onset neurodegenerative disorder with a heterogeneous clinical presentation. Verbal fluency is regularly used as a sensitive measure of language ability, semantic memory, and executive functioning, but qualitative changes in verbal fluency in FTD are currently overlooked. This retrospective study examined qualitative, linguistic features of verbal fluency in 137 patients with behavioral variant (bv)FTD (n = 50), or primary progressive aphasia (PPA) [25 non-fluent variant (nfvPPA), 27 semantic variant (svPPA), and 34 logopenic variant (lvPPA)] and 25 control participants. Between-group differences in clustering, switching, lexical frequency (LF), age of acquisition (AoA), neighborhood density (ND), and word length (WL) were examined in the category and letter fluency with analysis of variance adjusted for age, sex, and the total number of words. Associations with other cognitive functions were explored with linear regression analysis. The results showed that the verbal fluency performance of patients with svPPA could be distinguished from controls and other patient groups by fewer and smaller clusters, more switches, higher LF, and lower AoA (all p < 0.05). Patients with lvPPA specifically produced words with higher ND than the other patient groups (p < 0.05). Patients with bvFTD produced longer words than the PPA groups (p < 0.05). Clustering, switching, LF, AoA, and ND-but not WL-were differentially predicted by measures of language, memory, and executive functioning (range standardized regression coefficient 0.25-0.41). In addition to the total number of words, qualitative linguistic features differ between subtypes of FTD. These features provide additional information on lexical processing and semantic memory that may aid the differential diagnosis of FTD.

The item/order account of word frequency effects: Evidence from serial order tests

According to the item/order hypothesis, high-frequency words are processed more efficiently and therefore order information can be readily encoded. In contrast, low-frequency words are processed less efficiently and the focus on item-specific processing compromises order information. Most experiments testing this account use free recall, which has led to two problems: First, the role of order information is difficult to evaluate in free recall, and second, the data from free recall show all three possible patterns of results: memory for high-frequency words can be better than, the same as, or worse than that for low-frequency words. A series of experiments tested the item/order hypothesis using tests where the role of order information is less ambiguous. The item/order hypothesis predicts better performance for high- than low-frequency words when pure lists are used in both immediate serial recall (ISR) and serial reconstruction of order (SRO) tests. In contrast, when mixed (alternating) lists are used, it predicts better performance for low- than for high-frequency words with ISR tests, but equivalent performance with SRO tests. The experiments generally confirm these predictions, with the notable exception of a block order effect in SRO tasks: When a block of low-frequency lists preceded a block of high-frequency lists, a high-frequency advantage was observed but when a block of high-frequency lists preceded a block of low-frequency lists, no frequency effect was observed. A final experiment provides evidence that this block order effect is due to metacognitive factors.

Re-assessing age of acquisition effects in recognition, free recall, and serial recall

Age of acquisition (AoA) refers to the age at which a person learns a word. Research has converged on the conclusion that early AoA words are processed more efficiently than late AoA words on a number of perceptual and reading tasks. However, only a few studies have investigated whether AoA affects memory on recognition, serial recall, and free recall tests, and the results are equivocal. We took advantage of the recent increase in the number of high-quality norms and databases to construct a pool of early and late AoA words that were equated on numerous other dimensions. There was a late AoA advantage in recognition using both pure (Experiment 1) and mixed (Experiment 2) lists, no effect of AoA on serial recall of either pure (Experiment 3) or mixed (Experiment 4) lists, and no effect of AoA on free recall of either pure (Experiment 5) or mixed lists (Experiment 6). We conclude that AoA does reliably affect memory on some memory tasks (recognition), but not others (serial recall, free recall), and that no current account of AoA can explain the findings.

Verbal and Musical Short-Term Memory: Evidence for Shared Serial Order Processes?

This study explored the validity of an integrative framework for verbal and musical short-term memory (STM). Following this framework, access to domain-specific long-term knowledge bases supports the processing of musical and verbal item information in STM, while domain-general ordering processes support the representation of serial order information in the two domains. We exposed participants to verbal and musical STM tasks assessing either item information, order information, or both item and order information. Using an interindividual differences approach, we observed that performance in item-based STM tasks was not strongly associated between musical and verbal domains. In contrast, strong between-domain associations were observed for STM tasks assessing processing of verbal order and musical rhythm information. These preliminary results are overall in agreement with an integrative approach of verbal and musical STM. At the same time, the results highlight the difficulty of measuring serial order processing in the musical STM domain in a direct and specific manner.

On the Influence of Contextual Features for the Identification of Complex Words

This paper evaluates the effect of the context of a target word on the identification of complex words in natural language texts. The approach automatically tags words as either complex or not, based on two sets of features: base features that only pertain to the target word, and contextual features that take the context of the target word into account. We experimented with several supervised machine learning models, and trained and tested the approach with the 2016 SemEval Word Complexity Data Set. Results show that when discriminating base features are used, the words around the target word can supplement those features and improve the recognition of complex words.

A Picture Database for Verbs and Nouns with Different Action Content in Turkish

In this study we present a picture database of 160 nouns and 160 verbs. All verbs and nouns are divided into two groups as action and non-action words. Age of acquisition, familiarity, imageability, name agreement and complexity norms are reported alongside frequency, word length and morpheme count for each word. Data were collected from 600 native Turkish adults in total. The results show that although several measures have weak correlations with each other, only age of acquisition had moderate downhill relationships with familiarity and frequency with familiarity and frequency having a rather strong positive correlation with each other. The norms and the picture database are available as supplemental materials for use in psycholinguistic studies in Turkish.

Does learning to read shape verbal working memory?

Many experimental studies have investigated the relationship between the acquisition of reading and working memory in a unidirectional way, attempting to determine to what extent individual differences in working memory can predict reading achievement. In contrast, very little attention has been dedicated to the converse possibility that learning to read shapes the development of verbal memory processes. In this paper, we present available evidence that advocates a more prominent role for reading acquisition on verbal working memory and then discuss the potential mechanisms of such literacy effects. First, the early decoding activities might bolster the development of subvocal rehearsal, which, in turn, would enhance serial order performance in immediate memory tasks. In addition, learning to read and write in an alphabetical system allows the emergence of phonemic awareness and finely tuned phonological representations, as well as of orthographic representations. This could improve the quality, strength, and precision of lexical representations, and hence offer better support for the temporary encoding of memory items and/or for their retrieval.

Novel word acquisition in aphasia: Facing the word-referent ambiguity of natural language learning contexts

Recent research suggests that some people with aphasia preserve some ability to learn novel words and to retain them in the long-term. However, this novel word learning ability has been studied only in the context of single word-picture pairings. We examined the ability of people with chronic aphasia to learn novel words using a paradigm that presents new word forms together with a limited set of different possible visual referents and requires the identification of the correct word-object associations on the basis of online feedback. We also studied the relationship between word learning ability and aphasia severity, word processing abilities, and verbal short-term memory (STM). We further examined the influence of gross lesion location on new word learning. The word learning task was first validated with a group of forty-five young adults. Fourteen participants with chronic aphasia were administered the task and underwent tests of immediate and long-term recognition memory at 1 week. Their performance was compared to that of a group of fourteen matched controls using growth curve analysis. The learning curve and recognition performance of the aphasia group was significantly below the matched control group, although above-chance recognition performance and case-by-case analyses indicated that some participants with aphasia had learned the correct word-referent mappings. Verbal STM but not word processing abilities predicted word learning ability after controlling for aphasia severity. Importantly, participants with lesions in the left frontal cortex performed significantly worse than participants with lesions that spared the left frontal region both during word learning and on the recognition tests. Our findings indicate that some people with aphasia can preserve the ability to learn a small novel lexicon in an ambiguous word-referent context. This learning and recognition memory ability was associated with verbal STM capacity, aphasia severity and the integrity of the left inferior frontal region.

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.

Interaction Between Working Memory and Long-Term Memory

Individual differences in working memory have been related to interactions between working memory and long-term memory (LTM). The present study examined this interaction in children with and without language impairment. We used two listening span tasks and two nonword repetition tasks. The results suggest a strong interaction among age, language status, and task complexity. Children with specific language impairment showed consistently poor performance across tasks and indicated a weakness in using long-term knowledge to support working memory performance. The findings show that these children do not benefit from various manipulations designed to enhance working memory performance via LTM support due to a combination of inefficiencies in maintaining and updating items in working memory and retrieving information from LTM, in part because of their poor resistance to interference.

Implications of aging, lexicality, and item length for the mechanisms underlying memory span

Hulme, Maughan, and Brown (1991) provided evidence that the contribution of long-term memory to memory span performance was additive to the contribution of rehearsal rate (e.g., Baddeley, 1986). The present study further explored the relationship between these two contributions in younger and older adults. Speech rates and spans for short, medium, and long words and nonwords were obtained from subjects. Older adults had slower speech rates and smaller spans than did younger adults. Both groups' data were fit well by linear functions relating speech rates to spans. However, the slope of the function that relates speech rate to memory span was greater for words than for nonwords. This finding supports the idea that long-term memory, as well as rehearsal rate, contributes to span performance, and that this contribution is not simply additive.

Children with ASD can use gaze in support of word recognition and learning

BACKGROUND

Many children with autism spectrum disorders (ASD) struggle to understand familiar words and learn unfamiliar words. We explored the extent to which these problems reflect deficient use of probabilistic gaze in the extra-linguistic context.

METHOD

Thirty children with ASD and 43 with typical development (TD) participated in a spoken word recognition and mapping task. They viewed photographs of a woman behind three objects and simultaneously heard a word. For word recognition, the objects and words were familiar and the woman gazed ahead (neutral), toward the named object (facilitative), or toward an un-named object (contradictory). For word mapping, the objects and words were unfamiliar and only the neutral and facilitative conditions were employed. The children clicked on the named object, registering accuracy and reaction time.

RESULTS

Speed of word recognition did not differ between groups but varied with gaze such that responses were fastest in the facilitative condition and slowest in the contradictory condition. Only the ASD group responded slower to low frequency than high-frequency words. Accuracy of word mapping did not differ between groups, but accuracy varied with gaze with higher performance in the facilitative than neutral condition. Both groups scored above single-trial chance levels in the neutral condition by tracking cross-situational information. Only in the ASD group did mapping vary with receptive vocabulary.

CONCLUSIONS

Under laboratory conditions, children with ASD can monitor gaze and judge its reliability as a cue to word meaning as well as typical peers. The use of cross-situational statistics to support word learning may be problematic for those who have weak language abilities.

SKOOL versus ZOOL: effects of orthographic and phonological long-term memory on nonword immediate serial recall

In a now-classic study Besner and Davelaar (1982) reported an advantage of pseudohomophone (PSH) over nonword recall in a visual immediate serial recall (ISR) task, which remained under articulatory suppression (AS), and interpreted the findings as indicating PSH items obtain support from stored phonological long-term memory (LTM) representations even when phonological rehearsal is disrupted. However, one key question relating to this PSH effect remains: could the results have been contaminated by a potential confound of orthographic familiarity (i.e., PSH items often look like the word they sound like)? As a result, the present study examined the impact of orthography on PSH ISR. Our findings indicate that PSH accuracy was consistently higher for items that had an orthographic similarity to the parent word, and this effect did not interact with concurrent task. We therefore argue that PSH items in ISR obtain independent support from both orthographic and phonological LTM representations. The present study demonstrates the critical impact of orthographic LTM representations on visual nonword ISR, and we suggest that this may be a fruitful avenue for further research.

A common neural substrate for language production and verbal working memory

Verbal working memory (VWM), the ability to maintain and manipulate representations of speech sounds over short periods, is held by some influential models to be independent from the systems responsible for language production and comprehension [e.g., Baddeley, A. D. Working memory, thought, and action. New York, NY: Oxford University Press, 2007]. We explore the alternative hypothesis that maintenance in VWM is subserved by temporary activation of the language production system [Acheson, D. J., & MacDonald, M. C. Verbal working memory and language production: Common approaches to the serial ordering of verbal information. Psychological Bulletin, 135, 50-68, 2009b]. Specifically, we hypothesized that for stimuli lacking a semantic representation (e.g., nonwords such as mun), maintenance in VWM can be achieved by cycling information back and forth between the stages of phonological encoding and articulatory planning. First, fMRI was used to identify regions associated with two different stages of language production planning: the posterior superior temporal gyrus (pSTG) for phonological encoding (critical for VWM of nonwords) and the middle temporal gyrus (MTG) for lexical-semantic retrieval (not critical for VWM of nonwords). Next, in the same subjects, these regions were targeted with repetitive transcranial magnetic stimulation (rTMS) during language production and VWM task performance. Results showed that rTMS to the pSTG, but not the MTG, increased error rates on paced reading (a language production task) and on delayed serial recall of nonwords (a test of VWM). Performance on a lexical-semantic retrieval task (picture naming), in contrast, was significantly sensitive to rTMS of the MTG. Because rTMS was guided by language production-related activity, these results provide the first causal evidence that maintenance in VWM directly depends on the long-term representations and processes used in speech production.

The semantic-similarity effect in children: influence of long-term knowledge on verbal short-term memory

The present research was designed to highlight the relation between children's categorical knowledge and their verbal short-term memory (STM) performance. To do this, we manipulated the categorical organization of the words composing lists to be memorized by 5- and 9-year-old children. Three types of word list were drawn up: semantically similar context-dependent (CD) lists, semantically similar context-independent (CI) lists, and semantically dissimilar lists. In line with the procedure used by Poirier and Saint-Aubin (1995), the dissimilar lists were produced using words from the semantically similar lists. Both 5- and 9-year-old children showed better recall for the semantically similar CD lists than they did for the unrelated lists. In the semantic similar CI condition, semantic similarity enhanced immediate serial recall only at age 9 but contributed to item information memory both at ages 5 and 9. These results, which indicate a semantic influence of long-term memory (LTM) on serial recall from age 5, are discussed in the light of current models of STM. Moreover, we suggest that differences between results at 5 and 9 years are compatible with pluralist models of development.

Semantic contributions to immediate serial recall: evidence from two contrasting aphasic individuals

This paper examines the effect of semantic variables on serial recall in two contrasting aphasic cases and a group of controls. Experiment 1 manipulates word imageability and Experiment 2 manipulates semantic similarity. Controls not only showed better recall of imageable/semantically grouped lists, but under some conditions they also produced proportionately fewer phonological errors. These findings suggest that increasing the effectiveness of lexical/semantic support reduces reliance on phonological support. Consistent with this proposal, case TV, whose phonological impairment should increase his reliance on lexical/semantic support, produced abnormally low rates of phonological errors under some conditions. Conversely, case NP, who had a lexical/semantic impairment, produced abnormally high rates of phonological errors under some conditions. Analysis of serial recall curves in both aphasics and controls support the hypothesis that phonological processes are particularly critical for the recall of list-final items. However, there was no evidence that semantic support is especially crucial for list-initial recall. Controls did not exhibit stronger effects of semantic variables at list-initial position. Case NP (lexical/semantic impairment) performed disproportionately poorly on these items, but only under certain conditions.

Contributions of language and memory demands to verbal memory performance in language-learning disabilities

The purpose of this study is to investigate the performance of adults with language-based learning disorders (L/LD) and normal language controls on verbal short-term and verbal working memory tasks. Eighteen adults with L/LD and 18 normal language controls were compared on verbal short-term memory and verbal working memory tasks under low, moderate, and high linguistic processing loads. Results indicate no significant group differences on all verbal short-term memory tasks and verbal working memory tasks with low and moderate language loads. Statistically significant group differences were found on the most taxing condition, the verbal working memory task involving high language processing load. The L/LD group performed significantly worse than the control group on both the processing and storage components of this task. These results support the limited capacity hypothesis for adults with L/LD. Rather than presenting with a uniform impairment in verbal memory, they exhibit verbal memory deficits only when their capacity limitations are exceeded under relatively high combined memory and language processing demands.

EDUCATIONAL OBJECTIVES

The reader will (1) understand the relationship between increased linguistic demands and working memory, and (2) learn about working memory skills in adults with language learning disorders.

Lateral inferotemporal cortex maintains conceptual-semantic representations in verbal working memory

Verbal working memory, that is, the temporary maintenance of linguistic information in an activated state, is typically assumed to rely on phonological representations. Recent evidence from behavioral, neuropsychological, and electrophysiological studies, however, suggests that conceptual-semantic representations may also be maintained in an activated state. We developed a new semantic working memory task that involves the maintenance of a novel conceptual combination. Functional magnetic resonance imaging data acquired during the maintenance of conceptual combinations, relative to an item recognition task without the possibility of conceptual combination, demonstrate increased activation in the posterior left middle and inferior temporal gyri (known to be involved in conceptual representations) and left inferior frontal gyrus (known to be involved in semantic control processes). We suggest that this temporo-frontal system supports maintenance of conceptual information in working memory, with the frontal regions controlling the sustained activation of heteromodal conceptual representations in the inferior temporal cortex.

Concreteness Effects in Different Tasks: Implications for Models of Short-Term Memory

This study investigates concreteness effects in tasks requiring short-term retention. Concreteness effects were assessed in serial recall, matching span, order reconstruction, and free recall. Each task was carried out both in a control condition and under articulatory suppression. Our results show no dissociation between tasks that do and do not require spoken output. This argues against the redintegration hypothesis according to which lexical-semantic effects in short-term memory arise only at the point of production. In contrast, concreteness effects were modulated by task demands that stressed retention of item versus order information. Concreteness effects were stronger in free recall than in serial recall. Suppression, which weakens phonological representations, enhanced the concreteness effect with item scoring. In a matching task, positive effects of concreteness occurred with open sets but not with closed sets of words. Finally, concreteness effects reversed when the task asked only for recall of word positions (as in the matching task), when phonological representations were weak (because of suppression), and when lexical semantic representations overactivated (because of closed sets). We interpret these results as consistent with a model where phonological representations are crucial for the retention of order, while lexical-semantic representations support maintenance of item identity in both input and output buffers.

The Bristol norms for age of acquisition, imageability, and familiarity

Ratings of age of acquisition (AoA), imageability, and familiarity were collected for 1,526 words. The methodology made use of a modular approach, in which the full sample of words was divided into five separate blocks. Within each block, each word was rated on each of the three variables by 20 participants (undergraduate students from the University of Bristol). Analyses comparing these ratings to existing norm databases demonstrated that this methodology resulted in high reliability (assessed by Cronbach's a) and validity. The ratings were also transformed to be compatible with the Gilhooly and Logie (1980) norms. This transformation resulted in a set of norms for 3,394 words, which is by far the largest database of ratings forAoA, imageability,and familiarity t o date. The resulting databaseshould be useful for researchers interested in manipulating or controlling these factors in word recognition, neuropsychological, or memory studies. These norms can be downloaded from language.psy.bris .ac.uk/bristol_norms.html.

Dissociating word frequency and age of acquisition: The klein effect revived (and reversed)

The Klein effect (G. S. Klein, 1964) refers to the finding that high-frequency words produce greater interference in a color-naming task than low-frequency words. The present study used the Klein effect to investigate the relationship between frequency and age of acquisition (AoA) by measuring their influence on color naming. Two experiments showed reliable effects of frequency (though in the opposite direction to that reported by Klein) but no effects of AoA. Experiment 1 produced a dissociation between frequency and AoA when manipulated orthogonally. Experiment 2 produced the same dissociation using different stimuli. In contrast, both variables reliably influenced word naming. These findings are inconsistent with the view that frequency and AoA are 2 aspects of a single underlying mechanism.

Age-of-acquisition effects in word and picture identification

Words and pictures with earlier learned labels are processed faster than words and pictures with later learned labels. This age-of-acquisition (AoA) effect has been extensively investigated in many different types of tasks. This article provides a review of these studies including picture naming, word naming, speeded word naming, word pronunciation durations, lexical decisions, eye fixation times, face recognition, and episodic memory tasks. The measurement and validity of AoA ratings is discussed, along with statistical techniques used for exploring AoA's influence. Finally, theories of AoA are outlined, and evidence for and against the various theories is presented.

Redintegration and the benefits of long-term knowledge in verbal short-term memory: An evaluation of Schweickert’s (1993) multinomial processing tree model

The impact of four long-term knowledge variables on serial recall accuracy was investigated. Serial recall was tested for high and low frequency words and high and low phonotactic frequency nonwords in 2 groups: monolingual English speakers and French-English bilinguals. For both groups the recall advantage for words over nonwords reflected more fully correct recalls with fewer recall attempts that consisted of fragments of the target memory items (one or two of the three target phonemes recalled correctly); completely incorrect recalls were equivalent for the 2 list types. However, word frequency (for both groups), nonword phonotactic frequency (for the monolingual group), and language familiarity all influenced the proportions of completely incorrect recalls that were made. These results are not consistent with the view that long-term knowledge influences on immediate recall accuracy can be exclusively attributed to a redintegration process of the type specified in multinomial processing tree model of immediate recall. The finding of a differential influence on completely incorrect recalls of these four long-term knowledge variables suggests instead that the beneficial effects of long-term knowledge on short-term recall accuracy are mediated by more than one mechanism.

Specific impairment in developmental reading disabilities: a working memory approach

Children with developmental reading disabilities (RD) frequently display impaired working memory functioning. However, research has been divergent regarding the characteristics of the deficit. Our investigation addressed this controversy by assessing Baddeley's working memory model as a whole rather than focusing on particular aspects of it, as has been done by much of the research to date. Participants included 20 children with RD and 20 typical readers between the ages of 9 and 13. The phonological loop, visual-spatial sketchpad, and central executive were assessed according to Baddeley's model. The results demonstrated that children with RD have an impaired phonological loop but intact visual-spatial sketchpad and central executive functioning as compared to controls. In terms of the phonological loop, the deficit appears to be specific to the phonological store. Furthermore, our research supports a relationship between phonological processing and phonological loop functioning.

Both concreteness and age-of-acquisition affect reading accuracy but only concreteness affects comprehension in a deep dyslexic patient

As concreteness correlates very highly with the age-of-acquisition (AoA) of words, we attempted to disentangle the effects of these two variables in the oral reading and comprehension performance of the deep dyslexic patient LW. The results of a multiple regression analysis of LW's reading of 217 words showed that both AoA and concreteness affect reading accuracy, with the AoA effect being most apparent for her reading of concrete words. However, concreteness and not AoA affected LW's performance in matching spoken definitions to printed words, both when the distractors were semantically unrelated and when they were related. These data are interpreted in terms of a model of reading in deep dyslexia in which concreteness affects the ease with which semantics are accessed and can activate lexical representations, and AoA affects the ease with which lexical phonology becomes available for spoken word production.

Word-frequency and phonological-neighborhood effects on verbal short-term memory

Immediate memory span and maximal articulation rate were assessed for word sets differing in frequency, word-neighborhood size, and average word-neighborhood frequency. Memory span was greater for high- than low-frequency words, greater for words from large than small phonological neighborhoods, and greater for words from high- than low-frequency phonological neighborhoods. Maximal articulation rate was also facilitated by word frequency, phonological-neighborhood size, and neighborhood frequency. In a final study all 3 lexical variables were found to influence the recall outcome for individual words. These effects of phonological-word neighborhood on memory performance suggest that phonological information in long-term memory plays an active role in recall in short-term-memory tasks, and they present a challenge to current theories of short-term memory.

Language familiarity effects in short-term memory: the role of output delay and long-term knowledge

Four experiments examined the origins of language familiarity effects in bilingual short-term recall. In Experiments 1A and 1B, bilingual adults were tested on serial recall and probed serial recall of words and nonwords in their first and second languages. A first-language advantage was obtained on both measures, indicating that the beneficial effects of language familiarity are not exclusively attributable to lesser output delay during overt recall. In Experiments 2A and 2B, the same group of bilinguals was tested on serial recall and serial recognition of word lists in both languages. Although a sizeable first-language advantage was obtained on the serial recall measure, recognition performance was comparable in the two languages. On the basis of these results it is suggested that language differences in bilingual immediate memory arise in large part as a consequence of the differential availability of language-specific long-term knowledge with which to support retrieval processes in serial recall.

Remembering over the short-term: the case against the standard model

Psychologists often assume that short-term storage is synonymous with activation, a mnemonic property that keeps information in an immediately accessible form. Permanent knowledge is activated, as a result of on-line cognitive processing, and an activity trace is established "in" short-term (or working) memory. Activation is assumed to decay spontaneously with the passage of time, so a refreshing process-rehearsal-is needed to maintain availability. Most of the phenomena of immediate retention, such as capacity limitations and word length effects, are assumed to arise from trade-offs between rehearsal and decay. This "standard model" of how we remember over the short-term still enjoys considerable popularity, although recent research questions most of its main assumptions. In this chapter I review the recent research and identify the empirical and conceptual problems that plague traditional conceptions of short-term memory. Increasingly, researchers are recognizing that short-term retention is cue driven, much like long-term memory, and that neither rehearsal nor decay is likely to explain the particulars of short-term forgetting.

Complexity effects in visuo-spatial working memory: implications for the role of long-term memory

Several studies have shown that the capacity of visuo-spatial working memory is limited by complexity. Using a variant of the Corsi blocks task, this paper investigates the effect of complexity of the to-be-remembered path on visuo-spatial memory span. Redundancy was determined by three Gestalt principles: symmetry, repetition, and continuation. Experiment 1 revealed an effect of path complexity. The subsequent experiments explored whether the superiority for recall of structured over complex paths can be attributed solely to the operation of visuo-spatial working memory, or whether it also reflects the use of long-term knowledge. Experiment 2 demonstrated that the effect of complexity remained, even when the mechanisms for visuo-spatial coding were removed by a secondary visuo-spatial task. In Experiments 3 and 4 subjects were trained in the recall of complex paths. This led to the creation of long-term memory representations for these paths, as shown by an improvement in their span, and a concomitant lack of transfer to new paths. Finally, Experiment 5 showed that one prior repetition of a complex path was sufficient to produce specific and long-term learning effects. These results point to the involvement of long-term memory processes in the temporary retention of visuo-spatial material for which representations exist in long-term memory. They also suggest that the effect of complexity may provide a tractable technique for investigating the mechanisms underlying the limits of visuo-spatial short-term storage.

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.

Immediate serial recall of words and nonwords: tests of the retrieval-based hypothesis

In two experiments, the immediate serial recall of lists of words or nonwords was investigated under quiet and articulatory suppression conditions. The results showed better item recall for words but better order recall for nonwords, as measured with proportion of order errors per item recalled. Articulatory suppression hindered the recall of item information for both types of lists and of order information for words. These results are interpreted in light of a retrieval account in which degraded phonological traces must undergo a reconstruction process calling on long-term knowledge of the to-be-remembered items. The minimal long-term representations for nonwords are thought to be responsible for their lower item recall and their better order recall. Under suppression, phonological representations are thought to be minimal, producing trace interpretation problems responsible for the greater number of item and order errors, relative to quiet conditions. The very low performance for nonwords under suppression is attributed to the combination of degraded phonological information and minimal long-term knowledge.

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.

The effects of stimulus set size and word frequency on verbal serial recall

Two experiments are reported which examine immediate serial recall for high- and low-frequency words. The words in each list were either repeatedly drawn from the same small pool of candidates (in the closed set conditions) or each word only ever occurred once during the experiment (in the open set conditions). The results consistently show an effect of word frequency but the effect of set size was only apparent for low-frequency words. It is argued that both frequency and set size effects reflect processes concerning the "clean-up" of degraded short-term memory traces.

Age-of-acquisition and frequency effects in speeded word naming

An experiment was conducted to assess the importance of age-of-acquisition and frequency in a speeded word naming task, where participants were instructed to read aloud words before they disappeared from the computer screen. Under such speeded naming instructions, reading latencies were over 100ms (or 20%) faster than in "standard" (or immediate) word naming. There were clear effects of word frequency and age-of-acquisition under speeded naming. Compared to standard immediate naming, the age-of-acquisition effect was larger, with early-acquired words being speeded up more than late-acquired words, which is interpreted in terms of speeded naming reducing the contribution of sublexical processing to word naming times.

Age of acquisition, word frequency, and the role of phonology in the lexical decision task

In five experiments, we examined the respective roles of word age of acquisition (AoA) and frequency in the lexical decision task. The two variables were manipulated orthogonally (while controlling for concreteness and length) in fully factorial designs. Experiment 1 was a conventional lexical decision task, and Experiments 2-5 involved various attempts to interfere with reliance upon phonology. In Experiment 2, only orthographically illegal nonwords were used; in Experiment 3, pseudohomophone nonwords; in Experiment 4, articulatory suppression by the recitation of a nursery rhyme; and in Experiment 5, articulatory suppression by the repetition of a single word. The same basic pattern of results was observed in all experiments: There were main effects of both AoA and frequency, which interacted in such a way that the AoA effect was larger for low- than for high-frequency words. Although the AoA effect was reduced by manipulations intended to interfere with phonological processing, the manipulations did not eliminate the effect. The results are discussed in terms of current models of reading in which it is proposed that AoA has its primary effect on the retrieval of lexical phonology, which appears to be consulted automatically in the lexical decision task.

Semantic similarity and immediate serial recall: is there a detrimental effect on order information?

Four experiments investigated the disruptive effect of semantic similarity on short-term ordered recall. Experiments 1 and 2 contrasted immediate serial recall performance for lists of semantically similar items, drawn from the same semantic category, with performance for lists that contained items from different categories. Experiments 1 and 2 showed the usual similarity advantage for item information recall, but, contrary to expectations, there was no similarity disadvantage for the recall of order information even when the level of item recall was controlled. Experiments 3 and 4 replicate and extend these findings by using an order reconstruction task or a limited word pool strategy, both of which yield alternate measures of order retention. These findings clearly contradict the wide spread belief stating that semantic similarity hinders the short-term recall of order information. Results are discussed in the light of a retrieval-based account where the effects of semantic similarity reflect the processes called upon at recall: It is suggested that long-term knowledge is accessed to support the interpretation of degraded phonological traces.

Practitioner review: verbal working memory development and its disorders

Working memory refers to the systems responsible for the temporary storage and manipulation of information during the performance of cognitive tasks. There is a good deal of evidence that verbal short-term memory functions as a working memory system. We review advances in our understanding of the nature and limitations of verbal short-term memory and the reasons for its development with age, and go on to consider the common association between impairments of verbal short-term memory and other impairments of cognitive development. We conclude by considering the relationship between short-term memory development and cognitive development.