Errors in nonword repetition: bridging short- and long-term memory

According to the working memory model, the phonological loop is the component of working memory specialized in processing and manipulating limited amounts of speech-based information. The Children's Test of Nonword Repetition (CNRep) is a suitable measure of phonological short-term memory for English-speaking children, which was validated by the Brazilian Children's Test of Pseudoword Repetition (BCPR) as a Portuguese-language version. The objectives of the present study were: i) to investigate developmental aspects of the phonological memory processing by error analysis in the nonword repetition task, and ii) to examine phoneme (substitution, omission and addition) and order (migration) errors made in the BCPR by 180 normal Brazilian children of both sexes aged 4-10, from preschool to 4th grade. The dominant error was substitution [F(3,525) = 180.47; P < 0.0001]. The performance was age-related [F(4,175) = 14.53; P < 0.0001]. The length effect, i.e., more errors in long than in short items, was observed [F(3,519) = 108.36; P < 0.0001]. In 5-syllable pseudowords, errors occurred mainly in the middle of the stimuli, before the syllabic stress [F(4,16) = 6.03; P = 0.003]; substitutions appeared more at the end of the stimuli, after the stress [F(12,48) = 2.27; P = 0.02]. In conclusion, the BCPR error analysis supports the idea that phonological loop capacity is relatively constant during development, although school learning increases the efficiency of this system. Moreover, there are indications that long-term memory contributes to holding memory trace. The findings were discussed in terms of distinctiveness, clustering and redintegration hypotheses.

Errors in nonword repetition: bridging short- and long-term memory.

According to the working memory model, the phonological loop is the component of working memory specialized in processing and manipulating limited amounts of speech-based information. The Children's Test of Nonword Repetition (CNRep) is a suitable measure of phonological short-term memory for English-speaking children, which was validated by the Brazilian Children's Test of Pseudoword Repetition (BCPR) as a Portuguese-language version. The objectives of the present study were: i) to investigate developmental aspects of the phonological memory processing by error analysis in the nonword repetition task, and ii) to examine phoneme (substitution, omission and addition) and order (migration) errors made in the BCPR by 180 normal Brazilian children of both sexes aged 4-10, from preschool to 4th grade. The dominant error was substitution [F(3,525) = 180.47; P < 0.0001]. The performance was age-related [F(4,175) = 14.53; P < 0.0001]. The length effect, i.e., more errors in long than in short items, was observed [F(3,519) = 108.36; P < 0.0001]. In 5-syllable pseudowords, errors occurred mainly in the middle of the stimuli, before the syllabic stress [F(4,16) = 6.03; P = 0.003]; substitutions appeared more at the end of the stimuli, after the stress [F(12,48) = 2.27; P = 0.02]. In conclusion, the BCPR error analysis supports the idea that phonological loop capacity is relatively constant during development, although school learning increases the efficiency of this system. Moreover, there are indications that long-term memory contributes to holding memory trace. The findings were discussed in terms of distinctiveness, clustering and redintegration hypotheses.

Phonological short-term memory contributions to sentence processing in young children.

Two experiments investigated the contribution of phonological short-term memory to the processing of spoken sentences by 4- and 5-year-old children. In Experiment 1, sentences contained either short or longer words, and varied in syntactic structure. Overall, repetition but not comprehension of the sentences was significantly influenced by word length. In Experiment 2. children selected on the basis of their high phonological short-term memory ability were founded to be superior at repeating sentences to children of lower phonological short-term memory ability, although the two groups did not differ in their comprehension accuracy for the same sentences. In both experiments, comprehension and repetition performance were differently influenced by particular sentence structures. It is proposed that sentence repetition in children is constrained by phonological memory capacity, and is therefore directly influenced by memory-related factors that include the length and number of words in sentences, and individual differences in memory skills.

Block design performance in the Williams syndrome phenotype: a problem with mental imagery?

Williams syndrome (WS) is a rare genetic disorder which, among other characteristics, has a distinctive cognitive profile. Nonverbal abilities are generally poor in relation to verbal abilities, but also show varying levels of ability in relation to each other. Performance on block construction tasks represents arguably the weakest nonverbal ability in WS. In this study we examined two requirements of block construction tasks in 21 individuals with WS and 21 typically developing (TD) control individuals. The Squares tasks, a novel two-dimensional block construction task, manipulated patterns by segmentation and perceptual cohesiveness to investigate the first factor, processing preference (local or global), and by obliqueness to examine the second factor, the ability to use mental imagery. These two factors were investigated directly by the Children's Embeded Figures Test (CEFT; Witkin, Oltman, Raskin, & Karp, 1971) and a mental rotation task respectively. Results showed that individuals with WS did not differ from the TD group in their processing style. However, the ability to use mental imagery was significantly poorer in the WS group than the TD group. This suggests that weak performance on the block construction tasks in WS may relate to an inability to use mental imagery.

Everyday memory and cognitive ability in children born very prematurely.

In light of recent reports of episodic memory difficulties linked to early childhood hypoxia (Isaacs et al., 2000; Vargha-Khadem et al., 1997), preliminary findings of everyday memory function are reported for 20 children born at or before 32 weeks gestation, compared to 20 children born at term. Memory skills were assessed using the Rivermead Behavioural Memory Test for Children (Wilson, Ivani-Chalian, & Aldrich, 1991) at 5 years of age. Everyday memory problems were not found to be a general feature of children born prematurely, and performance was closely linked to receptive language ability but not general cognitive ability in both groups of children. Three children in the preterm group did obtain scores in the impaired range of the RBMT, and in two of these children memory impairment could not be predicted from their receptive language ability. This suggests an increased risk of everyday memory difficulties in populations of preterm children that may be enhanced in further studies by sampling children with greater risk of hypoxic insult.

Language differences in verbal short-term memory do not exclusively originate in the process of subvocal rehearsal.

Language differences in verbal short-term memory were investigated in two experiments. In Experiment 1, bilinguals with high competence in English and French and monolingual English adults with extremely limited knowledge of French were assessed on their serial recall of words and nonwords in both languages. In all cases recall accuracy was superior in the language with which individuals were most familiar, a first-language advantage that remained when variation due to differential rates of articulation in the two languages was taken into account. In Experiment 2, bilinguals recalled lists of English and French words with and without concurrent articulatory suppression. First-language superiority persisted under suppression, suggesting that the language differences in recall accuracy were not attributable to slower rates of subvocal rehearsal in the less familiar language. The findings indicate that language-specific differences in verbal short-term memory do not exclusively originate in the subvocal rehearsal process. It is suggested that one source of language-specific variation might relate to the use of long-term knowledge to support short-term memory performance.

Development of memory for pattern and path: further evidence for the fractionation of visuo-spatial memory.

Evidence from a number of sources now suggests that the visuo-spatial sketchpad (VSSP) of working memory may be composed of two subsystems: one for maintaining visual information and the other for spatial information. In this paper we present three experiments that examine this fractionation using a developmental approach. In Experiment 1, 5-, 8-, and 10-year old children were presented with a visuo-spatial working memory task (the matrices task) with two presentation formats (static and dynamic). A developmental dissociation in performance was found for the static and dynamic conditions of both tasks, suggesting that the activation of separable subsystems of the VSSP is dependent upon a static/dynamic distinction in information content rather than a visual/spatial one. A highly similar pattern of performance was found for a mazes task with static and dynamic formats. However, one strategic activity, the use of simple verbal recoding, may also have been responsible for the observed pattern of performance in the matrices task. In Experiments 2 and 3 this was investigated using concurrent articulatory suppression. No evidence to support this notion was found, and it is therefore proposed that static and dynamic visuo-spatial information is maintained in working memory by separable subcomponents of the VSSP.

Dissociable lexical and phonological influences on serial recognition and serial recall.

The impact of the lexicality of memory items on memory performance was compared in two paradigms, serial recall and serial recognition. Experiments 1 to 3 tested 7- and 8-year-old children. Memory accuracy was only mildly impaired in lists containing nonwords compared with words in a serial recognition task involving judgments of whether the items in two sequences were in the same order (Experiment 1), although a substantial advantage for word over nonword items from the same stimulus pool was found in serial recall (Experiment 2). A stronger influence of lexicality on serial recall than serial recognition was further demonstrated in Experiments 3A and 3B, and in 4A and 4B using adult participants. These experiments also established comparable degrees of sensitivity to the phonological similarity of the memory sequences in the two paradigms. The phonological similarity effect in serial recall was found to arise from increased phoneme order errors, whereas the lexicality effect was due principally to the greater frequency of phoneme identity errors for nonwords. It is proposed that the lexicality effect originates in the redintegration of item information just prior to recall, and that this process is largely bypassed in serial recognition.

Working memory deficits in children with low achievements in the national curriculum at 7 years of age.

BACKGROUND: Close links between children's capacities to store and manipulate information over brief periods have been found with achievements on standardised measures of vocabulary, language comprehension, reading, and mathematics. AIM: The study aimed to investigate whether working memory abilities are also associated with attainment levels in the national curriculum assessments at 7 years of age. SAMPLE: Eighty-three children aged 6 and 7 years attending local education authority schools participated in the study. METHODS: Working memory skills were assessed by a test battery designed to tap individual components of Baddeley and Hitch's (1974) working memory model. Children were assigned to normal and low achievement groups on the basis of their performance on national curriculum tasks and tests in the areas of English and mathematics. RESULTS: Children with low levels of curriculum attainment showed marked impairments on measures of central executive function and of visuo-spatial memory in particular. A single cut-off score derived from the test battery successfully identified the majority of the children failing to reach nationally expected levels of attainment. CONCLUSIONS: Complex working memory skills are closely linked with children's academic progress within the early years of school. The assessment of working memory skills may offer a valuable method for screening children likely to be at risk of poor scholastic progress.

Limitations in working memory: implications for language development.

In this study, the proposal that individual differences in spoken language acquisition may be due to limitations in short-term memory abilities was investigated within a working memory framework. The relationship speech production skills and working memory abilities was examined in two groups of 4-year-old children, matched for non-verbal ability but who had either relatively good or poor non-word repetition skills. Children with better non-word repetition skills produced speech that comprised a wider repertoire of words, on average longer utterances and a greater range of syntactic constructions than did children with relatively poor non-word repetition skills. The significant association found between these indices of language development and verbal short-term memory span assessed with non-spoken recall, suggested that this relationship was not merely due to the common output requirements of the language and memory tasks. Inconsistent associations between language performance and two tasks of visuo-spatial short-term memory precluded firm conclusions being drawn regarding the specificity of the relationship to the phonological domain. Cognitive mechanisms that may underlie the association between spoken language development and working memory skills are discussed.

Language-specific knowledge and short-term memory in bilingual and non-bilingual children.

The sensitivity of children's phonological short-term memory performance to language-specific knowledge was investigated in two experiments. In Experiment 1, monolingual English children, English-French bilingual children, and English children who were learning French as a second language were compared on measures of phonological short-term memory and vocabulary in the two languages. The children's short-term memory performance in each language mirrored their familiarity with English and French, with greater vocabulary knowledge being associated with higher levels of recall of both words and nonwords in that language. This finding was replicated in Experiment 2, in which two groups of children with good knowledge of English and French were examined: native bilingual children who had comparable knowledge of the two languages and non-native bilingual children who had a greater knowledge of their native than second language. The findings indicate that phonological short-term memory is not a language-independent system but, rather, functions in a highly language-specific way.

Phonotactic influences on short-term memory.

The impact of phonotactic probabilities on serial recall was investigated in a series of experiments. In Experiments 1A and 1B, 7 and 8 year olds were tested on their serial recall of monosyllabic words and of nonwords varying in phonotactic frequencies. A recall advantage to words over nonwords remained when stimuli were balanced for phonotactic probability, but nonword recall showed superior accuracy for high over low probability nonwords, as in Experiment 2. The nonword frequency effect appears to reflect the frequency of constituent syllables rather than biphones. Both lexicality and high phonotactic frequency led to increased proportions of full over partial recall of the memory stimuli. These findings indicate that decayed memory traces in phonological short-term memory can be reconstructed using either lexical or phonotactic knowledge.

Verbal and visuospatial short-term memory in children: evidence for common and distinct mechanisms.

This study was designed to identify whether verbal and visuospatial short-term memory performance in children is served by common or distinct mechanisms. Five- and 8-year-old children were tested on their verbal recall of spoken letter names and digits, and on their recall of tapped sequences of blocks. The performance of the children on the verbal and visuospatial serial recall tasks was largely unrelated, extending evidence for dissociable memory systems found in adults. Detailed characteristics of recall, such as serial position functions, migration patterns, and distribution of error types, were similar in the tasks requiring recall of letters and of blocks, although order errors predominated in the block but not the letter recall task for the older children. These results appear to reflect the application of common processes specialized for the extraction of serial order information from the phonological and visuospatial components of short-term memory.

Short-term memory and language outcomes after extreme prematurity at birth.

The performance of 26 children (3;0-4;0 years) who were born before 32 weeks gestation was compared with the performance of 26 full-term children on a range of short-term memory and language measures. The measures tested vocabulary, expressive language, phonological short-term memory, and general nonverbal ability. Preterm children scored more poorly across the full range of measures. The mildly depressed performance of the preterm group on the short-term memory and language measures was attributable to the large deficits on these tests shown by a subgroup of approximately one third of preterm children identified as being "at risk" for persisting language difficulties using the Bus Story Test (Bishop & Edmundson, 1987). The findings indicate that preterm birth and associated hazards may constitute a significant risk factor for specific language impairment in a sizable minority of children.

The development of memory.

This article reviews recent advances in understanding the changes in memory function that take place during the childhood years. Development of the following aspects of memory are considered: short-term memory, comprising phonological memory, visuospatial memory, and executive function; autobiographical memory; episodic memory, including eyewitness memory; and metamemory. Each of these aspects of memory function shows substantial qualitative change from infancy, through the preschool period, to the early school years. Beyond about 7 years of age, however, memory function appears adult-like in organisation and strategies, and shows only a gradual quantitative improvement through to early adolescence.

Phonological short-term memory and new word learning in children.

Sixty-five 5-year old children participated in 4 experimental tasks of word learning that varied systematically in the amounts of phonological and nonphonological learning required. Measures of the children's performances on 2 measures of phonological memory (digit span and nonword repetition), vocabulary knowledge, and nonverbal ability were also obtained. Learning of the sound structures of new words was significantly, and to some degree independently, associated with aspects of both phonological memory skill and vocabulary knowledge. Learning of pairs of familiar words was linked with current vocabulary knowledge, although not with phonological memory scores. The findings suggest that both existing lexical knowledge and phonological short-term memory play significant roles in the long-term learning of the sounds of new words. The study also provides evidence of both shared and distinct processes contributing to nonword repetition and digit span tasks.

Phonological working memory and speech production in preschool children.

This study investigates whether phonological working memory is associated with spoken language development in preschool children. Assessments were made of speech corpora taken from 3-year old children grouped in terms of their phonological memory abilities. Both quantitative and qualitative indices of the children's spontaneous speech output were taken in a structured play session. Significant differences were found, with children of good phonological memory abilities producing language that was more grammatically complex, contained a richer array of words, and included longer utterances than children of poor phonological memory abilities. The possible mechanisms by which phonological working memory skills are linked to the production of speech are considered.

Is nonword repetition a test of phonological memory or long-term knowledge? It all depends on the nonwords.

The extent to which children's performance on tests of nonword repetition is constrained by phonological working memory and long-term lexical knowledge was investigated in a longitudinal study of 70 children tested at 4 and 5 years of age. At each time of testing, measures of nonword repetition, memory span, and vocabulary knowledge were obtained. Reading ability was also assessed at 5 years. At both ages, repetition accuracy was greater for nonwords of high- rather than low-rated wordlikeness, and memory-span measures were more closely related to repetition accuracy for the low-wordlike than for the high-wordlike stimuli. It is argued that these findings indicate that nonword repetition for unwordlike stimuli is largely dependent on phonological memory, whereas repetition for wordlike items is also mediated by long-term lexical knowledge and is therefore less sensitive to phonological memory constraints. Reading achievement was selectively linked with earlier repetition scores for low-wordlike nonwords, suggesting a phonological memory contribution in the early stages of reading development. Vocabulary knowledge was associated with repetition accuracy for both low- and high-wordlike nonwords, consistent with the notion that lexical knowledge and nonword repetition share a reciprocal developmental relationship.