Dolors Girbau and Richard G. SchwartzJournal of Communication Disorders 41

(2008) 124-145

37-975-Challenges to Language Acquisition: Bilingualism and Language Impairment

December 2010

Phonological working memory in Spanish-English bilingual children with and without

specific language impairment

IntroductionIntroductionThe identification of Specific Language Impairment

continues to be a challenge for clinicians, even in older children (e.g., Spaulding, Planto, & Farinella, 2006).

Many children’s language impairments still go undiagnosed and, instead, intervention often focuses on poor academic achievement and reading disabilities, which are more readily identified.

There is, therefore, a need for further examination of measures that can reliably identify SLI in school-aged children.

Specific Language Impairment in Spanish-speaking children

The number of undetected children with SLI who speak languages other than English might be larger, even with recent attempts to improve the accuracy of this diagnosis (e.g., Crespo-Eguilaz & Narbona, 2003).

There are relatively few Spanish language assessment tools, despite the significant number of Spanish speakers in USA and worldwide (with more speakers than English).

This population has greater incidence of poverty and less education than the national average (Suro, 2005).

Bilingual proficiency varies across the sequential bilingual Hispanic population living in USA depending on many variables, such as language instruction at school, language spoken at home and with friends, years of residence in countries with L1 and L2, history of language deficits, socioeconomic status, length of exposure to the English, and how similar the two languages are.

English and Spanish have significant phonological, morphological and syntactic differences.

In Spanish, words are usually morphologically marked. Spanish-speaking children’s errors with verb morphology tend to be substitutions, unlike in English speakers who are more likely to omit verb inflections (Bedore and Leonard, 2000).

The transparent orthography of the Spanish language contrasts with the deep asymmetrical English orthography-phonology correspondence.

English has more vowel sounds than Spanish (five vowels).

Phonological Working Memory and SLI

Non-word repetition (NWR) is one of several tasks used by clinicians for distinguishing SLI children from their TLD peers.

Several studies have indicated that this task, which involves a shorter time than other language measures, is a reliable identifier of language impairment and the risk for language impairment in pre-school (e.g., Bishop, Adams, & Norbury, 2004) and primary-school children (e.g., Archibald & Gathercole, 2006a).

In NWR tasks, the child listens to a non-word, temporarily stores the novel phonological representation, and then produces it. The task involves the phonological loop which is a specialized subsystem of working memory with two components. The first component, phonological short-term storage maintains the incoming auditory sequence as a phonological code and the second component, subvocal rehearsal, holds this phonological representation avoiding its decay.

Children with SLI have an apparent deficit in phonological working memory(PWM) as exhibited by poorer repetition of non-words, particularly as the length of the non-words increases (e.g., Gathercole, 2006a, 2006b).

Aims of the studyThe present study examined the performance of sequential

bilingual children with and without SLI on the Spanish non-word repetition task developed by the researchers.

The researchers’ main goal was to determine the success with which that task can distinguish children with and without SLI in this bilingual context.

They also aimed to analyze the errors made by these children, and examine the relationship between NWR and scores from two language tests (one for each language).

The same task was administered to a subset of these children’s mothers as a pilot study, to determine whether the mothers of SLI children perform more poorly than the mothers of TLD children.

MethodMethodParticipants:

Most of the study participants were recruited from a dual language (English/Spanish) public school in NY. The rest were recruited through speech-language pathologists and by postings on internet and news papers.

Spanish was their L1 and English their L2.They all came from Spanish-speaking homes in NY with low/low-

middle socio-economic status. Both parents were monolingual speakers of Spanish (with some

exposure to English), and were born in Latin American Spanish-speaking countries.

The study population included 11 children with SLI and 11 age-matched children with TLD (7;6-10;10): 5 boys and 6 girls in each group.

SLI children were initially identified by speech pathologists. The presence of language impairments was further confirmed by the judgments of their teachers and parents. All were receiving intervention, except two children.

Each participant with SLI was matched on age (in years and months) and gender with a child with TLD, as closely as possible.

All children performed within normal limits on the Test of Nonverbal Intelligence (TONI-3; Brown et al., 1997), and passed a hearing screening.

A parent questionnaire was used to determine:

1. The extent to which Spanish was the primary language

2. Their socioeconomic status3. The family and child history for language deficits4. That the child did not have

a history of neurological disorders, behavior characteristic of autism.

The Primary English/Spanish language measures

The English CELF-3 Screening test (Semel, Wiig, & Secord, 1996) was administered as the primary English language measure.

The Spanish version of the Illinois Test of Psycholinguistic abilities (ITPA; Kirk et al., 2001) was the primary Spanish language measure. The researchers applied the ITPA with norms from Spain due to the scarce availability of Spanish tests with norms from USA for this age. It consisted of 11 individually administered subtests, which all were administered to the children, but only 4 subtests were selected as criteria for SLI: Auditory Comprehension, Auditory Association, Verbal Expression, and Grammatical Integration.

Twelve of the children’s mothers agreed to participate in the study. Seven of them had a child with SLI and five had a child with TLD.

Almost all mothers of children with SLI (6 out of 7) reported to

have one or more relatives with language and/or learning disabilities.

The English and Spanish versions of the Peabody Picture Vocabulary Test were administered to these mothers to get a comparative language measure in both languages (PPVT-III, Dunn & Dunn, 1997; TVIP, Dunn, Padilla, Lugo, & Dunn, 1986).

The Non-word repetition task The task followed the phonotactic patterns in the syllable structure, stress, and

the segments. It included 20 non-words, four at each of five syllable lengths (1,2,3,4,and 5

syllables). All the non-words began with consonants. They had a total of 184 segments: 14 in 1- s nw, 25 in 2and-s nw, 38 in 3-s nw,

48 in 4-s nw, and 59 in 5-s nw. 60 medium-low frequent different syllables were selected from a sample of

1148 syllables produced by 6-10 year old children and 1156 syllables produced by 6-13 year olds and from a list of more than 2500 Spanish syllables.

Each syllable contained only one vowel. None of the non-words contained any diphthongs. Twelve non-words included at least one cluster. The clusters were frequent in

Spanish words. Only one syllable in each word was stressed. All the Spanish sounds were included in the task.

ProcedureThe sessions were audio-recorded.The non-words were presented to the participants individually

through a computer with headphones so that they were seated on a side of the table without seeing the screen but the microphone of their recording.

Immediately after listening to each non-word, they had to repeat it.

An interstimulus interval was increased as the length of the non-word increased, which permitted sufficient time for the child’s repetition.

Each non-word was presented only one time.The entire task lasted approximately 3 min.

Instructions

“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 say the words once. Here comes the first word!”

Transcription and scoring

The participants’ productions were transcribed by the experimenter. A second judge independently transcribed the non-word productions of nine randomly selected children. The percentage of agreement between the two judges was 98.53%.

The number of correct words, the accuracy of the stress pattern as well as the frequency and types of overall consonant, consonant singleton, consonant cluster, and vowel errors were examined.

Each segment produced was categorized as one of the following:

•For the mothers, the analysis focused only on the overall accuracy of non-word production and the accuracy of 3-4-5 syllable non-words. Their errors were not further analyzed.

ResultsResults

CLEF-3

Auditory Comprehension

Auditory Association

Verbal Expression

Grammatical Integration

Overall MTotal

SLI-3.73 (2.44)-2.15 (1.50)-1.71 (0.75)-4.34 (1.85)-2.95 (1.09)-2.42 (0.67)

TLD-0.04 (0.66)-0.05 (0.51)-0.24 (0.67)0.04 (1.16)-0.07 (0.55)-0.19 (1.42)

ITPA

Mean standard deviations, in relation to mean scores from the norms (and Standard Deviations) for the Spanish ITPA and the English CELF-3 Screening Tests scores

•Fig.1 illustrates that the number of non-words produced correctly decreases with increases in the number of syllables. The graph includes the mean number of correct non-words and S.D. for each of five syllable lengths in both language groups of children.

Syllable Length of Nonwords

Mea

n N

umb

er o

f C

orre

ct N

onw

ords )0.65(

)0.83( )0.75(

)0.50(

)0.83()0.93(

)0.65(

)0.60()0.67(

)1.18(

The reproduction of the stress pattern for the non-words was almost always correct for the two groups of children, except for 5 non-word productions by children with SLI.

Thus the analysis focused on the percentage of correct non-words and correct segments, and the frequency of various error types.

Most of the errors occurred on the non-words that were 3,4, and 5 syllables in length. Therefore, a combined score for these non-words was examined as well.

SLISLITLDTLDSLISLITLDTLD

Correct ItemsCorrect Items

Non-words37.27 (8.76)55.91 (8.61)18.94 (13.48)42.42 (9.47)

Consonants73.31 (10.17)87.46 (3.96)70.53 (12.08)86.31(4.57)

Vowels91.06 (9.08)98.18 (2.03)90.06 (10.39)98.14 (2.07)

Clusters73.33 (17.33)83.64 (9.12)68.69 (23.84)80.20 (11.65)

Errors in Errors in consonantsconsonants

Substitutions14.88 (6.57)9.16 (3.84)15.73 (7.81)9.48 (4.28)

Omissions10.85 (6.91)3.52 (2.08)12.66 (7.93)4.28 (2.66)

Additions4.64 (2.87)3.18 (1.78)4.27 (2.80)2.73 (1.49)

Total non-wordsTotal non-words 3-4-53-4-5 syllable non-wordssyllable non-words

Mean (Standard Deviation) accuracy for non-word repetition

Relation to other Spanish and English language skills

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***

**

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Likelihood ratios for the percentage of correct non-words from the subgroup of 3-4-5 syllable non-words in children with SLI and TLD

Likelihood Likelihood ratioratio

NumberNumberProportionProportionNumberNumberProportionProportion

Children Children from USAfrom USA

<33.0%99/11=0.818211/11=0.09090.8182/0.0909=9.00

≥33.0%22/11=0.18191010/11=0.09090.1819/0.9091=0.20

Children Children from Spainfrom Spain

≤50.0%1111/11=111/11=0.09091/0.0909=11.0

>50.0%00/11=01010/11=0.09090/0.0909=0

SLISLI TLDTLD

Mean (Standard Deviations) accuracy for non-word repetition in a subgroup of children with SLI and TLD and their mothers: percentage of correct numbers

SLISLITLDTLDSLISLITLDTLD

MothersMothers39.29 (13.36)51.00 (4.18)23.81 (16.96)36.67 (7.46)

ChildrenChildren34.29 (7.87)57.00 (7.58)15.47 (10.31)43.33 (6.97)

Total non-wordsTotal non-words 3-4-53-4-5 syllable in non-wordssyllable in non-words

Spanish Test: Mothers of TLD children: M=96.60; Mothers of SLI children: M= 90.5.

English Test: Mothers of TLD children: M= 52.4; Mothers of SLI children: M=45.5.

Discussion The NWR TaskThe NWR task identified language status with

high degree of accuracy in bilingual Spanish L1 children.

The difference between the two groups was greater in longer non-words beginning with the three-syllable length.

These findings are similar to previous findings for children speaking other languages (e.g., Le Foll et al., 1995), including English and Spanish.

Error AnalysisThe two groups diverged significantly in the percentage of

consonant errors.The most frequent errors were consonant substitutions. This

finding is similar to previous findings for children of similar ages ( e.g., Marton & Schwartz, 2003).

The SLI group made significantly more substitution and omission errors.

Although they made less vowel errors, the SLI children did not approach the ceiling scores reached by the TLD group. This could be due to the limited vowel inventory of Spanish (only 5), and the fact that vowels are fully acquired earlier in development than the complete consonant inventory. But it also might indicate that vowels are preferentially preserved in this PWM task in SLI and TLD children.

The relation between the NWR task and the two standardized language tests ( CELF-3 and ITPA)

NWR was highly correlated with three of the four ITPA subtests. The reason might be that these tasks have auditory working memory demands similar to the NWR task.

The Verbal Expression task did not correlate significantly with the NWR task, because this subtest makes more demands on long-term memory than on working memory.

There was no significant correlation between the NWR task and CELF-3, maybe because it assesses L2 skills in these children. The correlation, however, approached significance because two of the CELF-3 tasks make direct demands on working memory.

The SES FactorIn the present study, the likelihood ratios led the

authors to set a 33% correct non-word repetition cut-off, whereas in a previous study they conducted in Spain, with a higher SES population, the cut-off was 50%.

There is evidence that SES has some effect on language development and academic achievement (e.g., Schuele, 2001). It may have an even greater impact on the fragile language and working memory abilities of children with SLI.

Performance of the mothersThe mothers with SLI children performed more poorly than

the mothers of TLD children for the set of 20 non-words and for the subset of 3-4-5 syllable non-words.

Future research is needed with a larger number of parents (mothers and fathers) to examine the potential use of this NWR task in parents as another marker of SLI.

It may be possible to identify parents whose children are at risk of SLI at an earlier age than the children might be testable.

It might also provide further information about the heritability of NWR deficit as a clinical marker of SLI.

ConclusionsConclusionsThe NWR task following the phonotactic patterns

of Spanish is an accurate identifier of SLI for Spanish-speaking children from 8 to 10 years of age.

Length effects were found in 3-4-5 syllable non-words.

Phonological working-memory abilities, as measured by NWR, were strongly related to comprehension and production skills in the children’s native language.