International Journal of Language & Communication Disorders

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International Journal of Language & Communication Disorders

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Non-word repetition in Spanish-speaking children with Specific Language Impairment (SLI) To link to this article: DOI: 10.1080/13682820600783210 URL: http://dx.doi.org/10.1080/13682820600783210

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INT. J. LANG. COMM. DIS., JANUARY–FEBRUARY VOL.

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2007,

1, 59–75

Research Report Non-word repetition in Spanish-speaking children with Specific Language Impairment (SLI) Downloaded By: [Girbau, Dolors] At: 21:47 23 January 2007

Dolors Girbau{ and Richard G. Schwartz{ {Jaume I University, Castello´, Spain {City University of New York, New York, NY, USA (Received 7 October 2005; accepted 24 April 2006)

Abstract Background: A number of previous studies have revealed that children with Specific Language Impairment have limitations in Phonological Working Memory as revealed by a task that requires them to repeat non-words of increasing syllable length. However, most published studies have used nonwords that are phonotactically English. Aims: The purpose was to examine the repetition of non-words that are consistent with the phonotactic patterns of Spanish. The study also examined the relationship between non-word repetition performance and other language measures. Methods & Procedures: Eleven Spanish-speaking children with Specific Language Impairment and 11 age-matched children with typical language development aged 8;3–10;11, who were part of a larger study of sentence processing, participated in the study. The primary data were the children’s repetition of 20 non-words, four at each syllable length (one, two, three, four and five syllables). The children’s productions were transcribed and scored for non-word, segmental and cluster accuracy as well as for error type. Outcomes & Results: The children with Specific Language Impairment performed more poorly on almost all measures of accuracy, but particularly in their production of three-, four-, and five-syllable non-words. Substitutions were the most frequent error type for both groups. Likelihood ratios indicated that non-word repetition performance is a highly accurate identifier of language status in these preselected groups. The children’s non-word repetition was highly correlated with most of the standardized language measures that were administered to the children. Conclusions: The repetition of non-words consistent with Spanish phonotactics reveals word-length effects and error patterns similar to those found in previous Address correspondence to: Dolors Girbau, Department of Basic Psychology, University Jaume I, Campus Riu Sec, 12071 Castello´, Spain; e-mail: [email protected]

International Journal of Language & Communication Disorders ISSN 1368-2822 print/ISSN 1460-6984 online # 2007 Royal College of Speech & Language Therapists http://www.informahealthcare.com DOI: 10.1080/13682820600783210

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Dolors Girbau and Richard G. Schwartz studies. It extends these findings to older school-age Spanish-speaking children with Specific Language Impairment. Given the limited choices for instruments that can be used to identify children with Specific Language Impairment, a Spanish Non-word Repetition Task has the potential to be a valuable screening test for clinical and research purposes. Keywords: Specific language impairment (SLI), non-word repetition, children, Spanish speakers, psycholinguistic abilities, Phonological Working Memory.

Downloaded By: [Girbau, Dolors] At: 21:47 23 January 2007

What this paper adds Children with Specific Language Impairment (SLI) have limitations in Phonological Working Memory as revealed by English non-word tasks. Few studies have extended Non-word Repetition Task to children over 8 years of age or other languages. A non-word task that followed the phonotactic patterns of Spanish was created. This task has the potential to be a valuable screening test for detecting Specific Language Impairment in Spanish-speaking children; children with Specific Language Impairment performed more poorly in several measures. Introduction English-speaking children with SLI have apparent deficits in Phonological Working Memory as revealed by a number of tasks including the repetition of non-words (e.g. Montgomery 2002). Scores on this particular task often identify a child’s language status with a high degree of accuracy (Dollaghan and Campbell 1998). However, the approaches to this task and the findings concerning the performance of children with SLI vary substantially. Furthermore, most of the research concerning non-word repetition in children with SLI has focused on English-speaking children with nonwords that resemble real English words to varying degrees. Although non-word repetition or reading has been adapted to some other languages (Le Foll et al. 1995, Saito 1995, Sahleń et al. 1999, Van Bon and Van der Pijl 1997, Maridaki-Kassotaki 2002, Carreiras and Perea 2004), including Spanish, a non-word repetition task has not been applied to Spanish-speaking children with SLI. This has potential importance for several reasons. It will further confirm findings from previous studies (e.g. Le Foll et al. 1995, with 16 non-words) that the word length effects and overall performance deficits in children with language impairments extend to languages other than English. We also hoped to create a non-word set with Spanish phonotactic characteristics that might ultimately be used to identify children with SLI for research or clinical purposes. Early studies of non-word repetition by children with SLI (e.g. Gathercole and Baddeley 1990, Gathercole et al. 1994), revealed that these children had particular difficulties repeating non-words that were three or more syllables in length. Nonword repetition requires that the child perceives and temporarily stores an unfamiliar sequence of syllables and segments, constructs a novel phonological representation, and produces one or more novel syllables. Some of the sequences of individual segments may not be completely novel, a point to which we will return below. Baddeley’s (1986, 1996, 2003a,b) working memory model includes a specialized subsystem called the phonological loop. It has two components: phonological

Non-word repetition in Spanish SLI

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short-term storage, which holds the incoming auditory sequence as a phonological code, and subvocal rehearsal, which maintains this phonological representation preventing its decay. Many investigators (e.g. Gathercole and Baddeley 1990, Baddeley 1996, 2000a,b, Dollaghan and Campbell 1998, Ellis Weismer et al. 2000, Marton and Schwartz 2003) have used Non-word Repetition Tasks to identify impairments in Phonological Working Memory (PWM) in children with SLI, as a clinical marker of SLI (Bishop et al. 1996, Conti-Ramsden and Hesketh 2003), and as the basis for claiming that storage limitations in PWM may underlie some of the deficits observed in children with SLI (e.g. Gathercole and Baddeley 1990, Montgomery 2002). Several different Non-word Repetition Tasks have been developed to assess children’s PWM. One of the more widely used Non-word Repetition Tasks, The Children’s Test of Non-word Repetition (CNRep), includes 40 non-words (e.g. ballop, pennel, doppelate, blonterstaping), ten at each length from two to five syllables (Gathercole et al. 1994). The non-words follow English phonotactic and stress patterns. The non-words are presented via live voice in random order and the child is instructed to repeat each non-word exactly as it was heard. The test has been normed on 612 children with typical language development (TLD) between 4;0 and 9;0. Gathercole et al. (1994) reported developmental changes in typically developing children between the ages of 4 and 8 years. If PWM has access to long-term storage of phonological representations for words, the use of English morphological endings and syllables that were actually English words in the CNRep items might facilitate the performance of TLD children and impair the performance of children with SLI. Dollaghan and Campbell (1998) constructed pairs of non-words that were identical except for a single segment; the stressed syllable of one was a real word, while the stressed syllable of the other token was not a word. Typically developing children (aged 9;10–12;0) repeated non-words with syllables that corresponded to real words significantly more accurately than non-words with ‘non-lexical’ syllables. The Non-word Repetition Task (NRT) (Dollaghan and Campbell 1998) contains 16 non-words ranging in length from one to four syllables. Although the non-words were phontactically legal in their segmental content, they were prosodically non-English in that each syllable was equally stressed and all vowels were tense or, in some cases, diphthongs (e.g. naib, vatchaip, doitauvab, tavatchinaig). The NRT was initially administered to 40 children (aged 6;0–9;9). Half of the children had SLI and half were age-matched children with TLD. Children with SLI were less accurate than their age-matched controls, particularly on the three- and four-syllable non-words. In a second study, likelihood ratios revealed that a total percentage of phonemes correct of 70% or below successfully identified children as SLI, whereas a score of 81% or above identified a child as typically developing, with a high degree of confidence. Dollaghan and Campbell argued that the structure of the non-words they employed and the nature of the task provided a culturally and linguistically unbiased assessment tool. The CNRep and the NRT, the two most commonly used Non-word Repetition Tasks, differ in several ways. The CNRep includes syllables that are real words and English morphological endings, whereas the NRT includes no real words or morphological affixes. Notably, the NRT non-words are segmentally English, but do not resemble any stress-timed language. The CNRep uses two- to five-syllable targets, whereas the NRT uses one- to four-syllable targets. The scoring on the NRT

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Dolors Girbau and Richard G. Schwartz


is more sensitive, using a percentage of phonemes correct, whereas the CNRep scores whole non-words as correct or incorrect. The CNRep uses a live-voice presentation (in some experiments investigators have used audio-recorded versions of the stimuli), whereas the NRT has been used experimentally with audio-recorded stimuli. It is unclear whether these non-words could be produced by a speaker of English or any other stress-timed language without imposing a prosodic structure that would reduce some of the tense vowels to lax vowels. The CNRep has been normed, but the NRT does not have published a set of norms. One additional feature of the stimuli in non-word repetition that appears to influence non-word repetition performance is the phonotactic probability of the syllables (Munson et al. 2005). Children with phonological disorders are less accurate in repeating non-words that have phonotactically infrequent segment sequences. A number of studies have established relations of varying degrees between nonword repetition and other measures of language, as well as the use of non-word repetition as a marker of language impairment. For example, children with SLI (mean age of 10;11) who had the highest non-word repetition scores, had better basic reading and reading comprehension scores, than children with SLI who had the lowest non-word repetition scores (Botting and Conti-Ramsden 2001). These groups did not differ in their expressive vocabulary or their receptive vocabulary scores. However, Montgomery (2004) found no association between sentence comprehension and non-word repetition for either SLI or TLD children (Montgomery 2004). In typically developing children (aged 3;2–8;10), non-word repetition was found to be more accurate in a larger-vocabulary group than in a smaller-vocabulary one (Edwards et al. 2004). Receptive vocabulary was also associated with non-word repetition scores for 3–5-year olds (Metsala 1999). Four-year-old TLD children with better non-word repetition skills produced speech with a larger repertoire of words, had longer utterances, and a greater range of syntactic constructions than 4-year-old children with relatively poor non-word repetition skills (Adams and Gathercole 2000). In Swedish preschool children with language impairments, there was a correlation between non-word repetition and four comprehension measures (Sahleń et al. 1999). This study employed a Non-word Repetition Task with non˚ kesson words that followed Swedish phonotactic patterns (Barthelom and A 1995). In Greek-speaking children (aged 6–9 years), results revealed strong links between reading performance and non-word repetition scores (Maridaki-Kassotaki 2002). Also, Dutch poor readers (aged 9.8–11.8 years) showed a pseudoword repetition deficit when they were compared with normal readers (aged 7.7– 9.4 years) scoring in the same range on a word-reading test (Van Bon and Van der Pijl 1997). Several studies (Dollaghan and Campbell 1998, Briscoe et al. 2001, ContiRamsden and Hesketh 2003, Gray 2003, Bishop et al. 2004, Roy and Chiat 2004) have found that non-word repetition is a reliable and accurate identifier of language impairments or the risk of language impairment in preschool children. Roy and Chiat (2004) also reported a strong correlation between non-word repetition and measures of vocabulary comprehension. When preschool children with SLI (mean55;0) were compared with younger, language-matched children with TLD (mean52;10), percentile repetition scores identified children with SLI, but the raw scores did not differentiate the groups (Conti-Ramsden and Hesketh 2003).


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In somewhat older children, Ellis Weismer et al. (2000) replicated the earlier findings of Dollaghan and Campbell (1998), although the likelihood ratios were not as large. The only studies that have focused on children over 8;0 have provided a set of normative data for the CNRep (Botting and Conti-Ramsden 2001, Simkin and Conti-Ramsden 2001) and have compared children with SLI who have very high and very low repetition scores. These data are somewhat limited because of ceiling effects. The average score was 38 out of 40 non-words correct with an apparent normal range of 35–40. Out of 242 children with SLI, 14 (6%) had scores above the 84th percentile. When compared with 14 children with SLI, matched for IQ, who scored below the 16th percentile, significant correlations with the group were found between most of the language tests and performance on the Non-word Repetition Task with the exception of expressive and receptive vocabulary tests. To date, relatively few studies have extended non-word repetition to languages other than English. The further establishment of Phonological Working Memory deficits cross-linguistically through non-word repetition is important for several reasons. It will further confirm the fact that this deficit is not unique to Englishspeaking children with SLI and that the deficits are seen in the repetition of nonwords that have syllable structures other than closed syllable pattern. The purpose of the present study was to devise a task involving non-words consistent with the phonotactic patterns of Spanish. We created non-words that reflected Spanish prosodic patterns and included Spanish syllables. We focused on 8–10-year-old Spanish children (for whom instruments identifying Specific Language Impairment are needed), who were part of a larger study of sentence processing (Schwartz and Girbau in preparation). We also examined the relationship between non-word repetition performance and other language measures. Previous research has revealed correlations of varying strength between non-word repetition and measures such as expressive and receptive vocabulary, reading skills, sentence and story comprehension, utterance length, and syntactic complexity. The conflicting findings concerning some of these relations (e.g. expressive and receptive vocabulary) may be due to methodological differences and would benefit from additional investigation. Method Recruiting and subject selection Children were recruited from two middle/middle-low socio-economic status public schools in Castello´, Spain. The main teaching language at school was Spanish and the participants came from Spanish-speaking homes. The children also understood Catalan. In the Valencia region, there is a diglossic bilingualism: Spanish is considered the formal language and Catalan a non-formal language, so that there are many passive bilinguals who are Spanish users and understand Catalan. Testing There are two main standardized language tests available in Spanish, a version of the CELF-4 (Wiig et al. 2006) with limited normative data and the Spanish adaptation of

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the Illinois Test of Psycholinguistic Abilities (ITPA, Kirk et al. 2001). Because the CELF-4 has limited normative data in Spanish, we used the ITPA with norms from Spain. It consists of 11 individually administered subtests (some of them different from the English version). Although all subtests were administered, we selected four subtests as criteria for SLI because these focused on those characteristics of language production and comprehension that most closely correspond to those tested by more contemporary language tests. In the Auditory Comprehension subtest, the child listens to very brief stories and responds to questions about the stories by pointing to pictures. In the Auditory Association subtest, the child completes sentences spoken by the examiner (e.g. ‘The father is big, the child is … (small)’). The Verbal Expression subtest is a lexical fluency task; the child is given a series of categories (e.g. animals, fruits) and is asked to say as many items in the stated category as possible in one minute. In the Grammatical Integration subtest, the child completes sentences spoken by the examiner according to related pictures (e.g. ‘Here there is a dog, here there are two … (dogs)’). As for the intelligence, the SLI children were administered the Wechsler Intelligence Scale for Children — Revised (WISC-R; Wechsler 2001) and four children were also administered the Test of Nonverbal Intelligence (TONI-2; Brown et al. 2000). The typically developing children were administered the Baterıá de Aptitudes Diferenciales y Generales (BADYG E2; Yuste 2002). All children passed a hearing screening and their parents completed a questionnaire that determined the extent to which Spanish was the primary language, socio-economic status, a family history of language deficits, and whether the child had a history of neurological disorders, or behaviours characteristic of autism. Participants A school psychologist identified and referred 28 children with language impairments (excluding articulation disorders). Seventeen were eliminated because: five children did not meet one or more of the criteria for SLI (including performance IQ above 75); Spanish was not their first language (seven children); or the child or parents decided not to participate (five children). We also eliminated 16 of the 27 TLD children that were tested because their ITPA (four children) or IQ (two children) scores did not fit the criteria, because the child or parents decided not to participate (six children) or Spanish was not their first language (four children). Eleven children with SLI and 11 children with TLD, aged 8;3–10;11, participated. There were seven boys and four girls in each group. Each SLI participant was matched for gender and age with a TLD child. The average for the difference in age within each pair of children was mean521.55 months [SLI age – TLD age] with standard deviation (SD)53.53. The mean age of SLI group was 9;5, mean5113.09 months, SD58.54 months (ranging from 99 to 131). For the TLD group, mean59;6 (mean5114.64 months, SD57.88 months), ranging from 103 to 127 months. For each child, we calculated a mean of the z-scores for each of selected subtests of the Spanish ITPA (Table 1). The children with SLI who were included all scored: (1) below zero on the average z-score of these four language-relevant subtests; and (2) at least 21.0 SD below the means on at least two of the four selected subtests. The children with TLD who were included all scored: (1) above zero on the average

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Table 1. Mean standard deviations (in relation to mean scores from the norms) and standard deviations for Illinois Test of Psycholinguistic Abilities (ITPA) test scores Auditory comprehension


Specific Language Impairment (SLI) Typically developing language (TLD)

22.00 (1.76)

Auditory association

Verbal expression

21.24 (1.17) 21.03 (0.94)

0.13 (0.39)

0.72 (0.47)

0.58 (0.81)

Grammatical integration

Overall mean

21.04 (1.55)

21.33 (0.50)

0.57 (0.49)

0.50 (0.29)

z-score of these four language-relevant subtests; and (2) scored more than 21.0 SD from the mean on any of the four selected subtests (Table 1). The children with SLI had performance IQs based on the WISC-R (Wechsler 2001) ranging from 75 to 104 (mean581.5, SD58.78). Five of the children were also administered the TONI-2 (Brown et al. 2000). Their WISC-R performance scores were 75, 77, 77, 84 and 104, and their respective TONI-2 scores were 85, 83, 83, 97 and 132. We can only speculate that their scores all would have been close to or above 85 (the more current typical cut-off for SLI with English normed tests), if we had used the TONI-2 across all the subjects. Their SLI status was also confirmed by the judgements of their teachers and parents, which appears to be a highly reliable indicator of language status (Restrepo 1998). All children with SLI were receiving intervention at the schools or through private services. The children with TLD had performance intelligence percentiles ranging from 35 to 97 (mean573.73, SD516.68), on the basis of the school collectively administered BADYG E2 test (Yuste 2002). We transformed percentile scores into standard scores with mean5100 (SD515) so that we had an approximated IQ to compare the two language groups. The children with TLD had performance intelligence IQs ranging from 94 to 128 (mean5111.08, SD59.19). It is clear that the distributions overlap, but that there were children in the TLD group who had higher performance scores as is typical in age-matched groups. Non-word Repetition Task A Non-word Repetition Task was constructed following Spanish phonotactic patterns in the syllable structure and the segments included. There were 20 nonwords, four at each of five syllable lengths (one, two, three, four and five syllables). All non-words began with consonants. The pseudo-words had a total of 184 segments: 14 segments in one-syllable non-words, 25 in two-syllable non-words, 38 in three-syllable non-words, 48 in four-syllable non-words and 59 in five-syllable non-words. Sixty medium-low frequent different syllables were selected from a sample of 1148 syllables produced by 6–10-year-old children (Justicia et al. 1996) and 1156 syllables produced by 6–13-year-olds (Justicia 1995), and from a list of more than 2500 Spanish syllables (Armario Toro 2001). Each syllable contained only one vowel; the highest frequent syllables were excluded. The medium and low frequent syllables were combined in different orders within a pseudo-word. None of the non-words contained any diphthongs. Twelve non-words included at least one cluster; these non-words were distributed according to the syllable lengths: two in each of the one- to three-syllable non-word lists, and three at both four- and five-syllable lengths. The clusters that were included are very frequent in Spanish

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words (e.g. /bl/, /c /, /p /, all with a tapped / /). All the Spanish sounds were included on the task, except the / / and /w/ [n˜, w], which occur very infrequently. The stress in the non-words varied across four different syllable positions: ultimate, penultimate, antepenultimate, and before the antepenultimate, (e.g. /muń.ti /, /gi. en.flo´.nis/). More examples of the non-words at each syllable length are given in Table 2. The instructions and the 20 non-words were digitally recorded using Cool Edit Pro (2002; Syntrillium Software Corporation) by the first author who is a native speaker of Spanish. The average duration of a non-word at each length was: one-syllable non-words, mean5445 ms, SD551 ms; two-syllable nonwords, mean51015 ms, SD5110 ms; three-syllable, mean51332 ms, SD5130 ms; four-syllable, mean51621 ms, SD5137 ms; and five-syllable, mean51890 ms, SD5143 ms. An interstimulus interval was left to allow the child’s repetition. Each word was presented only one time. The entire task lasted approximately 3 min. Procedure The sessions were videotaped. The non-words were presented to the children individually through a computer with headphones. Immediately after listening to each non-word, the child had to repeat it. Instructions Each child was given the following instructions: ‘Ahora voy a decirte varias palabras divertidas que son inventadas. Despue´s de escuchar cada palabra inventada tu´ tienes que repetı´rmela exactamente tal como la has oı´do; la debes repetir igual. Algunas palabras son cortas y otras largas. Escucha muy bien, porque so´lo puedo decirte cada palabra una vez. Esta es la primera palabra.’ (I am going to say some funny made-up words. Your job is to say them back to me, exactly the way you hear them. Some of the words are short, and others are longer. Listen carefully, because I can only say the words once. Here comes the first word.) Transcription and scoring The children’s productions were transcribed from the videotapes by the experimenter. To assess transcription reliability, a second judge independently transcribed the non-word productions of six randomly selected children. This represented Table 2. Phonetic transcription /flıń/ /hole´ / /konscenb a´l/ /gi enflońis/ /kleptasmaho´ fun/

Examples of the non-words for each syllable length Orthographic transcription flıń zo.lle´r cons.cen.bra´l gui.ren.flo´.nis clep.tas.ma.zo´r.fun


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approximately 27% of the sample. The percentage of agreement between two judges for segment transcription (1106 segments) was 99.19%. The children’s productions were analysed segment-by-segment as: vowels, consonants (including the two consonants of each cluster), and clusters. In most cases we were easily able to match the segments in child’s production to the target segments, syllable-by-syllable. In a small number of cases the syllable sequence and structure did not match that of the target. In these cases we judged whether syllables had been transposed or whether segments had migrated. Each segment produced was categorized as one of the following: (1) correct — the child’s production matches the adult target in the same serial position within the syllable (or only involves a minor distortion in pronunciation); (2) substitution — the child substitutes a segment for the adult target in the same serial position within the syllable; (3) omission — a consonant or vowel in the adult target did not appear in the child’s production; (4) addition — a segment that is not present in the matching target syllable was produced (e.g. /muń.ti s/ for /muń.ti /). When matching the child’s produced syllables and segments with their targets was more challenging, we followed a set procedure. We first attempted to align the syllable sequence produced by the child to the target, using the matching vowels (child’s production/target) as syllable anchors because vowels were produced more accurately. If there were no matching vowels, the matching consonants were used as syllable anchors. If the child produced two syllables that could be matched with one target syllable, only the most similar syllable was scored. If the syllable produced had a matching cluster and it was a partial or total fusion of two target syllables, the matching clusters were used as syllable anchors and it was only scored for the target syllable with the cluster. Within a syllable, when one target segment could potentially be matched with more than one error segment in the child’s production (e.g. an apparent substitution and an addition), the produced segment that was more similar to the target was classified as substitution. Results The two language status groups (SLI/TLD) did not differ significantly in age, F(1, 20)50.195, p50.66. Therefore, the age variable was not considered in any of the subsequent analyses. The focus of the analyses was on the number or percentage of correct non-words and correct segments. We also examined the frequency of various error types. Non-word repetition accuracy An examination of our data revealed that most errors occurred on the non-words that were three, four, and five syllables in length, similar to previous reports. So, in addition to the total scores typically examined in Non-word Repetition Tasks, we examined a combined score for three-, four-, and five-syllable non-words (3-4-5). Because many of the derived scores were at or near ceiling, we did this to avoid statistical comparisons of ceiling effects to non-ceiling scores. We transformed all percentages using arcsine prior to statistical analysis. A series of one-way analyses of variance (ANOVAs) revealed that the groups differed in the percentage of total number of non-words correct [F(1, 20)59.78, p50.005 ], in the 3-4-5 composite

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Figure 1. Mean number of correct non-words for each of five syllable lengths.

[F(1, 20)59.25, p50.006] and in the three- [F(1, 20)55.30, p50.03], four- [F(1, 20)510.24, p50.004 ], and five-syllable non-words [F(1, 20)510.24, p50.004]. Figure 1 shows that the number of non-words produced correctly decreases with increases in the number of syllables. The difference was also significant using an IQadjusted model of ANCOVA (with IQ as a covariate and language group as a fixed factor), for the percentage of total number of non-words correct [F(2, 19)55.21, p50.015 ], and the 3-4-5 composite [F(2, 19)54.76, p50.021]. Segmental accuracy and types of errors We examined the overall correct percentages of consonants, vowels and clusters as well as the respective subscores across the three-, four-, and five-syllable non-words (Table 3). We transformed all percentages using arcsine prior to statistical analysis. Vowels were rarely produced inaccurately by children in either group. The average percentage of vowel errors as well as the individual scores for the TLD children were consistently at floor. Consequently, we did not analyse these data statistically. The children with SLI made vowel errors; one child with percentage correct as low as 81.67%. Even scores below 100% correct are noteworthy, given the consistently perfect performance of the children with TLD (only one child scored below, with 98.33%). The children with SLI made more consonant errors overall [F(1, 20)510.89, p50.004] and in the 3-4-5 syllable non-words [F(1, 20)512.61 p50.002]. This was also true using an IQ-adjusted model of ANCOVA, overall [F(2, 19)56.05, p50.009] and in the 3-4-5 syllable composite [F(2,19)56.97 p50.005]. They also made more errors on clusters than the children with TLD overall [F(1, 20)58.35, p50.009 for the ANOVA, and F(2, 19)54.82, p50.020 for the ANCOVA] and in the 3-4-5 syllable non-words [F(1, 20)56.62, p50.018 for the ANOVA, and F(2, 19)54.39, p50.027 for the ANCOVA]. We also examined the percentage of consonants that were omitted or substituted. Substitutions were the most frequent error type for both groups

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Non-word repetition in Spanish SLI Table 3.

Mean (standard deviation) accuracy for non-word repetition Non-words total specific language impairment (SLI)

Mean (SD)


Correct items Non-words Consonants Vowels Clusters

49.09 81.96 95.61 77.58

Errors in consonants Substitutions Omissions Additions

11.66 (7.34) 6.45 (6.67) 2.73 (1.62)

(17.72) (11.45) (6.96) (15.85)

3-4-5 Syllable

Typically developing language (TLD) 76.36 95.16 99.85 94.55

(7.78) (3.29) (0.50) (5.82)

3.81 (2.82) 1.03 (1.15) 2.00 (1.18)

SLI 30.30 79.28 95.39 72.93

(17.59) (11.83) (7.19) (19.55)

13.45 (7.60) 7.37 (7.26) 2.09 (1.64)

TLD 71.21 94.40 99.85 92.53

(10.78) (3.82) (0.50) (8.73)

4.36 (3.35) 1.23 (1.29) 1.09 (0.70)

For the consonants categories, each cluster was counted as two consonants. All categories are presented as percentages except additions, which are presented as frequencies.

(Table 3). These percentages were transformed by arcsine prior to statistical analysis. The children with SLI produced more substitutions than the children with TLD overall [F(1, 20)524.90, p50.00007 for the ANOVA, and F(2, 19)512.59, p50.0003 for the ANCOVA] and in the 3-4-5 syllable non-words [F(1, 20)526.95, p50.00004 for the ANOVA, and F(2, 19)513.71, p50.0002 for the ANCOVA]. The same was true for omissions overall [F(1, 20)510.54, p50.004 for the ANOVA, and F(2, 19)55.19, p50.015 for the ANCOVA] and for the 3-4-5syllable non-words [F(1, 20)511.08, p50.003 for the ANOVA, and F(2, 19)55.44, p50.013 for the ANCOVA]. There was no group difference for the frequency of consonant additions according to the ANOVA, F(1, 20)51.45, p50.24 (Table 3). Likelihood ratios We calculated likelihood ratios (Sackett 1992, Sackett and Haynes 2002) to determine the extent to which non-word repetition can accurately distinguish children with and without SLI. It is important to note that likelihood ratios are somewhat inflated by their derivation from preselected groups of children with SLI and TLD than from a general population of as yet unidentified children. The likelihood ratios were calculated using the percentage of correct non-words for the subgroup of three-, four- and five-syllable non-words. It is the likelihood that a given test result would be expected in a patient with the target disorder compared with the likelihood that that same result would be expected in a patient without the target disorder. For TLD children, if the percentage of correct non-words (for the subgroup of three-, four- and five-syllable non-words) is greater than 50.0%, the likelihood ratio is 0.00, with a negative predictive value of 100%. Negative predictive value represents the probability that a child does not have SLI following a negative test result. For the children with SLI, if the percentage of correct non-words (for the subgroup of three-, four- and five-syllable non-words) is lower than or equal to 50.0%, the likelihood ratio is 11.00 with a positive predictive value of 91.67%. Clinically, positive predictive value represents the probability of having SLI given a positive test result. It refers to the proportion of persons identified as positive on

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the screening test who actually have the disorder. The post-test probability is 91.67% (pre-test odds51; post-test odds511). The sensitivity (or true positive rate) of the Spanish Non-word Repetition Task is 1.00. The sensitivity of a test concerns its ability to identify people with the disorder in question, in this case SLI. It reflects the proportion of children with SLI correctly identified (‘true positives’) by the test. A sensitive test is one that provides a minimum of false negatives (i.e. children with SLI who are not detected by the screening measure). The specificity of non-word repetition is 0.91. The specificity (or true negative rate) of the test refers to its ability to accurately identify people who do not have SLI. It reflects the proportion of TLD (non-SLI) children correctly identified (‘true negatives’). A specific test provides a minimum of false positives (i.e. non-SLIs identified by the screening test as SLIs). As a general rule, screening tests tend to emphasize maximizing sensitivity over specificity. For people screening positive, additional testing is done to determine the presence and severity of a problem. Relation to other language abilities Beyond the general accuracy with which non-word repetition scores identify language status, we were interested in the relations between these scores and the standardized tests scores we had collected. We calculated Pearson Product Moment Correlations between the overall non-word repetition percentages or the 3-4-5 syllable composite percentages and the raw scores of the four ITPA subtests as well as an overall mean of these subtests (see Figure 2).The mean of the four ITPA subtests highly correlated with both of the non-word repetition scores. The same

Figure 2. Pearson correlations between the four subtests of the Illinois Test of Psycholinguistic Abilities (ITPA) test (including the overall mean) and the percentage of correct non-words in the Non-word Repetition Task: *p,0.002, **p,0.0002 and ***p,0.00002. The significant p-value starts at p50.005 (that is, 0.05/10) using the Bonferroni method, because the p-value needs to be adjusted since ten correlations were conducted.


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was true for the individual Auditory Association and Grammatical Integration scores. The Verbal Expression and the Auditory Comprehension subtests were not significantly correlated with either of the non-word repetition percentages, after using an adjusted p-value (Figure 2). Relation to performance intelligence abilities Downloaded By: [Girbau, Dolors] At: 21:47 23 January 2007

We also analysed the relation between non-word repetition percentages (arcsine transformed) and the Performance IQs from the WISC-R (for children with SLI) and the BADYG E2 test (for children with TLD). Specifically, we calculated Pearson Product Moment Correlations between these IQ scores and both the overall nonword repetition percentages (r50.40) and the 3-4-5 syllable composite percentages (r50.40). No significant association was found. This means that IQ accounts only for 16% (0.402 * 100) of variance between the two language groups. Discussion The findings were that, as in English-speaking children, Spanish-speaking children with SLI have considerably greater difficulty than their age-matched peers in repeating non-words as the number of syllables in those pseudo-words increases. It was also found that their performance first diverges at three-syllable non-words, as in previous studies at similar ages (Dollaghan and Campbell 1998, Montgomery 2004), and in younger children (Ellis Weismer et al. 2000, Rodekohr and Haynes 2001). The mean percentage of consonant substitutions, the most frequent error type, was more than three times higher in children with SLI than in children with TLD. The mean percentage of consonant omissions, although less frequent than consonant substitutions, was also significantly higher in children with SLI than in the TLD group (six times higher in children with SLI than in children with TLD). The analysis of covariance demonstrated that these findings cannot be attributed to the performance IQ differences between the groups. Strong correlations were found between the Spanish Non-word Repetition Task and two of the subtests of the Spanish ITPA: Auditory Association and Grammatical Integration. These correlations are not surprising. Auditory Association and Grammatical Integration involve auditory/oral sentence completion (without and with visual support, respectively), which certainly make demands on working memory. The high strengths of these correlations are not usual in reports of the relationship between non-word repetition and other measures of language, but these particular skills have not been examined specifically in previous studies. After adjusting the p-values to 0.005, there was no significant correlation with Verbal Expression scores (a lexical fluency subtest that requires the child to produce words in specific categories). A number of previous studies have reported correlations between non-word repetition and measures of vocabulary comprehension (Gathercole and Baddeley 1990, Montgomery 2002, Roy and Chiat 2004). In older children with SLI, non-word repetition scores were not related to expressive nor receptive vocabularies (Botting and Conti-Ramsden 2001). In typically developing children, a expressive/receptive vocabulary has been found to be associated with non-word repetition (Metsala 1999, Adams and Gathercole 2000, Edwards et al. 2004). The correlation with the Auditory Comprehension was not significant. Some investigators (e.g. Gathercole and Baddeley

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1990, Sahleń et al. 1999, Montgomery 2002) have reported a correlation between measures of language comprehension and non-word repetition. No significant correlations were found between any of the two Spanish Nonword Repetition Task scores and the Performance Intelligence measures. There may be some concern because the children with TLD, as usual, have higher IQs than the children with SLI. Although this may play some role in non-word repetition performance, our findings indicate that it only accounts for a small percentage (16%) of the variance between the two language groups. The Spanish Non-word Repetition Task has the potential to be a valuable screening test for detecting SLI in Spanish-speaking children. The percentage of correct non-words seems to be a very good predictor of language status that can be easily and reliably calculated. The cut-off of 50% correct for the 3-4-5syllable non-words accurately discriminates between children with and without SLI. In the English NRT (Dollaghan and Campbell 1998), with non-words ranging in length from one to four syllables, the cut-off points were 70% for children with SLI and 81% for children with TLD correct total phonemes (5;8–12;2). The percentage of correct non-words as a SLI marker simplifies scoring markedly and, thus, may be much easier to apply it clinically. It is important to reiterate that the likelihood ratios were somewhat inflated because they were derived from preselected groups of SLI and TLD children rather than from a yet unidentified group of children. The present study adds to a large body of literature concerning the non-word repetition skills of children with language impairments and provides additional data concerning the non-word repetition of older children. It also expands the somewhat smaller literature concerning non-word repetition for children who speak languages other than English. Spanish represents an important addition because of the greater variety of prosodic patterns and because it is primarily an open syllable language. Thus, it confirms that non-word repetition deficits cannot be ascribed to the closed syllable, trochaic pattern of English. With the establishment of these effects in languages, it may be possible to compare the repetition of non-words with native and non-native phonotactic patterns as a way of examining the effects of phonological representation on non-word representation. This would add a cross-linguistic perspective to the recent work by Munson et al. (2005) who demonstrated effects of phonotactic probability in English. The development of a Non-word Repetition Task in Spanish has significant clinical relevance, not only for monolingual Spanish-speaking children, but also for bilingual children. For example, it could be used as a screening device that might distinguish between a language difference versus a disorder in a bilingual child referred for evaluation because of English language deficits. In summary, it was found that a Non-word Repetition Task following the phonotactic patterns of Spanish yielded the same length effects as reported by previous investigators in other languages (e.g. Gathercole and Baddeley 1990, Gathercole et al. 1994, Le Foll et al. 1995, Van Bon and Van der Pijl 1997). It appears to be an accurate identifier of SLI for Spanish-speaking children from 8 to 10 years of age in this group of children. More work is needed before this task can be used clinically. A much larger sample of children needs to be tested to ensure that the findings and cut-off levels generalize to the population of Spanish-speaking children with SLI. It would also be interesting to expand the age of the children tested to insure that it is also accurate across a wider range of ages.


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Acknowledgements


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