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

Disentangling Processing and Storage Accounts of Working Memory Development in Childhood

Researchers have been asking the question of what drives the development of working memory (WM) during childhood for decades. This question is particularly challenging because so many aspects of cognition develop with age that it is difficult to disentangle them and find out which factors are causal or fundamental. In this review, we first prepare to discuss this issue by inquiring whether increases in storage, processing, or both are the fundamental driving factor(s) of the age-related increase in WM capability in childhood. We contend that by experimentally manipulating either factor and observing changes in the other, it is possible to learn about causal roles in WM development. We discuss research on school-aged children that seems to suggest, by means of such an approach, that the growth of storage is causal for some phases or steps in WM tasks, but that the growth of processing is causal for other steps. In our theoretical proposal, storage capacity of the focus of attention determines earlier steps of information processing by constraining the selective encoding of information into WM, whereas processing dependent on the focus of attention determines later steps, like the detection of patterns that can simplify the effective memory load and adoption of a proactive stance of maintenance in dual-task settings. Future directions for research are discussed.

Predictors of processing-based task performance in bilingual and monolingual children

In the present study we examined performance of bilingual Spanish-English-speaking and monolingual English-speaking school-age children on a range of processing-based measures within the framework of Baddeley's working memory model. The processing-based measures included measures of short-term memory, measures of working memory, and a novel word-learning task. Results revealed that monolinguals outperformed bilinguals on the short-term memory tasks but not the working memory and novel word-learning tasks. Further, children's vocabulary skills and socioeconomic status (SES) were more predictive of processing-based task performance in the bilingual group than the monolingual group. Together, these findings indicate that processing-based tasks that engage verbal working memory rather than short-term memory may be better-suited for diagnostic purposes with bilingual children. However, even verbal working memory measures are sensitive to bilingual children's language-specific knowledge and demographic characteristics, and therefore may have limited clinical utility.

Absolute and proportional measures of potential markers of rehearsal, and their implications for accounts of its development

Previous studies of the development of phonological similarity and word length effects in children have shown that these effects are small or absent in young children, particularly when measured using visual presentation of the memoranda. This has often been taken as support for the view that young children do not rehearse. The current paper builds on recent evidence that instead suggests that absent phonological similarity and word length effects in young children reflects the same proportional cost of these effects in children of all ages. Our aims are to explore the conditions under which this proportional scaling account can reproduce existing developmental data, and in turn suggest ways that future studies might measure and model phonological similarity and word length effects in children. To that end, we first fit a single mathematical function through previously reported data that simultaneously captures absent and negative proportional effects of phonological similarity in young children plus constant proportional similarity effects in older children. This developmental function therefore provides the benchmark that we seek to re-produce in a series of subsequent simulations that test the proportional scaling account. These simulations reproduce the developmental function well, provided that they take into account the influence of floor effects and of measurement error. Our simulations suggest that future empirical studies examining these effects in the context of the development of rehearsal need to take into account proportional scaling. They also provide a demonstration of how proportional costs can be explored, and of the possible developmental functions associated with such an analysis.

Phonological and lexical effects in verbal recall by children with specific language impairments

BACKGROUND & AIMS

The present study examined how phonological and lexical knowledge influences memory in children with specific language impairments (SLI). Previous work showed recall advantages for typical adults and children due to word frequency and phonotactic pattern frequency and a recall disadvantage due to phonological similarity among words. While children with SLI have well-documented memory difficulties, it is not clear whether these language knowledge factors also influence recall in this population.

METHODS & PROCEDURES

Sixteen children with SLI (mean age = 10;2) and chronological age-matched typically developing children (CAM) controls recalled lists of words differing in phonological similarity, word frequency and phonotactic pattern frequency. While previous studies used a small set of words appearing in multiple word lists, the current study used a larger set of words, without replacement, so that children could not gain practice with individual test items.

OUTCOMES & RESULTS

All main effects were significant. Interactions revealed that children with SLI were affected by similarity, but less so than their peers, comparably affected by word frequency and unaffected by phonotactic pattern frequency.

CONCLUSIONS & IMPLICATIONS

Results due to phonological similarity suggest that children with SLI use less efficient encoding, while results due to word frequency and phonotactic pattern frequency were mixed. Children with SLI used coarse-grained language knowledge (word frequency) comparably with peers, but were less able to use fine-grained knowledge (phonotactic pattern frequency). Paired with phonological similarity results, this suggests that children with SLI have difficulty establishing robust phonological knowledge for use in language tasks.

Phonological and Visuospatial Short-Term Memory in Children With Specific Language Impairment

An investigation was carried out into the phonological short-term memory (PSTM) and visuospatial short-term memory (VSSTM) skills of children with specific language impairment (SLI; n = 41) using memory span tasks. Individuals with SLI were compared with children who had milder degrees of language difficulty (“low language functioning” [LLF]; n = 31) and children with typical development (n = 88). Regression analyses examined the effects of group after controlling for age and nonverbal IQ; further regressions included an additional control for verbal IQ. Even after controlling for all of these variables, children with SLI and LLF showed significantly weaker PSTM than children with typical development. For VSSTM, there were no overall group differences in performance. The findings imply that the PSTM difficulties that have been reported in children with SLI are substantial, whereas VSSTM appears to be an area of relative strength for most children with SLI.

Working memory and educational achievement in children with intellectual disabilities

BACKGROUND

There is little previous research examining whether measures of working memory are related to educational achievement in children with intellectual disabilities (ID).

METHODS

A battery of working memory and achievement measures was administered to 11- to 12-year-old children with ID; younger typically developing children of comparable mental age were also assessed.

RESULTS

The working memory measures that assessed phonological short-term memory (PSTM) accounted for the most variance in reading and spelling in children with ID, whereas the working memory measures that assessed central executive-loaded working memory (CELWM) accounted for the most variance in number skills. These relationships were broadly similar among typically developing children.

CONCLUSIONS

Compensatory strategies for weak PSTM may help to improve reading and spelling skills in children with ID, whereas reducing CELWM loads may be more helpful in aiding their number skills.

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.

Different Interference Effects in Musicians and a Control Group

In the present study musicians and normal control subjects performed an S1-S2 pitch comparison task, which included the presentation of intervening tones during the retention interval. The time for encoding and storing the pitch of S1 was varied between 200 and 1,500 ms by changing the pause between the S1 offset and the onset of the intervening tones. Although musicians outperformed the control group with longer pauses after the S1 offset, this advantage was relatively small with shorter pauses. These results suggest that the advantage of musicians in storing auditory information is not solely due to their superior encoding of information but also to improved working memory operations.

Probed serial recall in Williams syndrome: lexical influences on phonological short-term memory

Williams syndrome is a genetic disorder that, it has been claimed, results in an unusual pattern of linguistic strengths and weaknesses. The current study investigated the hypothesis that there is a reduced influence of lexical knowledge on phonological short-term memory in Williams syndrome. Fourteen children with Williams syndrome and 2 vocabulary-matched control groups, 20 typically developing children and 13 children with learning difficulties, were tested on 2 probed serial-recall tasks. On the basis of previous findings, it was predicted that children with Williams syndrome would demonstrate (a) a reduced effect of lexicality on the recall of list items, (b) relatively poorer recall of list items compared with recall of serial order, and (c) a reduced tendency to produce lexicalization errors in the recall of nonwords. In fact, none of these predictions were supported. Alternative explanations for previous findings and implications for accounts of language development in Williams syndrome are discussed.

Language influences on verbal short-term memory performance in Down syndrome: item and order recognition

Down syndrome is associated with severe deficits in language and verbal shortterm memory, but the causal relationship between these deficits is unclear. The current study therefore investigated the influence of language abilities on verbal short-term memory performance in Down syndrome. Twenty-one individuals with Down syndrome and 29 younger typically developing children were tested on memory for words and nonwords using 2 immediate recognition tasks: an order memory task that was a relatively pure measure of verbal short-term memory and an item memory task that was more sensitive to language ability. Despite having superior vocabulary knowledge to the typically developing children, individuals with Down syndrome were impaired on both order and item tasks. This impairment was particularly marked on the item task, where individuals with Down syndrome showed an atypically large lexicality effect. These results are interpreted in terms of an underlying verbal short-term memory deficit in Down syndrome that is compounded by poor phonological discrimination abilities.