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Bilingual Children With Nonsyndromic Cleft Lipand/or Palate: Language and Memory Skills

Selena Ee-Li Young,a,b Alison Anne Purcell,b Kirrie Jane Ballard,bSusan Jane Rickard Liow,c Sara Da Silva Ramos,d and Robert Heardb

Purpose: Research shows that monolingual children with cleftlip and/or palate (CLP) have a higher incidence of cognitive-linguistic deficits, but it is not clear whether bilingual preschool childrenwith CLP are especially vulnerable because they need to acquire2 languages. We tested the hypothesis that bilingual children withCLP score lower than bilingual childrenwith typical development (TD)on receptive vocabulary, verbal memory, and visuospatial memory.Method: Participants were 86 bilingual CLP children and 100 TDchildren 3–6 years of age, dominant in English or Mandarin. Eachchild completed assessments of English and Mandarin vocabulary,verbal and visuospatial short-term and working memory, hearing,and articulation.Results: With analysis of covariance controlling for age anddominant language, no group differences were found between

the CLP and TD bilingual children, although a correlational analysisindicated discrepancies in the relationship between variables.Conclusions: The findings do not support the hypothesis thatpreschool children with CLP score lower than preschool childrenwith TD on receptive vocabulary andmemorymeasures. Longitudinalresearch examining literacy skill development is needed to establishwhether the deficits reported for school-age monolingual childrenwith CLP become more obvious in bilingual children in later years,especially when the medium of instruction is the child’s nondominantlanguage.

Key Words: cleft lip and palate, language, working memory,children, bilingual

R esearch on the communication skills in monolin-gual children with nonsyndromic cleft lip and/orpalate (CLP) has predominantly focused on articu-

lation (D’Antonio & Scherer, 1995; Henningsson et al.,2008), resonance (Kuehn & Moller, 2000), pragmatics(Chapman, Graham, Gooch, & Visconti, 1998), language(Fox, Lynch, & Brookshire, 1978; Nash, Stengelhofen,Toombs, Brown, & Kellow, 2001; Priester & Goorhuis-Brouwer, 2008), and learning disorders (Richman,1980; Richman & Eliason, 1986), with fewer studies in-vestigating specific cognitive abilities such as phonolog-ical awareness (Collett, Leroux, & Speltz, 2010; Collett,

Stott-Miller, Kapp-Simon, Cunningham, & Speltz, 2010)and short-term memory (STM; Eliason & Richman,1990; Richman, Eliason, & Lindgren, 1988; Richman &Ryan, 2003). In these few studies, the cognitive-linguisticabilities of monolingual children with CLP have rangedfrom normal (Broen, Devers, Doyle, Prouty, & Moller,1998; Collett, Leroux, & Speltz, 2010) to deficient whencompared with age-peers without CLP (Chapman, 2011;Collett, Stott-Miller, et al., 2010; Richman&Ryan, 2003).Nevertheless, most researchers have uncovered variablecognitive-linguistic performance in monolingual childrenwith CLP (see review below), and to our knowledge,there has been no work examining how bilingual chil-dren with CLP progress. Children who learn two lan-guages before puberty are the majority worldwide(Tucker, 1998); hence, the need to examine the cognitive-linguistic performance of bilingual children with CLPwould be relevant to a significant number of children in-ternationally. Bilingual children with CLP may possiblyshow different cognitive and linguistic behavioral charac-teristics compared with monolingual children with CLPbecause of their learning of two languages. For this rea-son, a clearer understanding of the prevalence and na-ture of cognitive deficits in bilingual children with CLPis needed to ensure adequate and early identification of

aKandang Kerbau Hospital, SingaporebUniversity of Sydney, New South Wales, AustraliacNational University of SingaporedHeriot-Watt University, Edinburgh, Scotland

Correspondence to Selena Ee-Li Young:[email protected]

Editor: Janna OettingAssociate Editor: Katherine Hustad

Received November 16, 2010Revision received June 26, 2011Accepted February 15, 2012DOI: 10.1044/1092-4388(2012/10-0320)

Journal of Speech, Language, and Hearing Research • Vol. 55 • 1314–1328 • October 2012 • D American Speech-Language-Hearing Association1314

childrenwho require a comprehensive framework of lan-guage and cognitive intervention.

Clefts of the lip andpalateare oneof themost commoncongenital defects resulting from genetic and environ-mental causes, with 77% of CLP occurring in isolationor without a documented syndrome (i.e., nonsyndromic;International Perinatal Database of Typical Oral CleftsWorking Group, 2011). Individuals with CLP all requirelong-term multidisciplinary intervention to repair thecleft and to remediate interrelated disorders in facialgrowth, dentition, communication, hearing, feeding,and psychosocial development. The worldwide incidenceis estimated to range from 0.13 to 2.53 (per 1,000 livebirths), with the highest incidence in Asian and AmericanIndian populations, and the lowest levels in African popu-lations (Wyszynski, 2002). The incidence in Singapore,the setting for this study, is one of the highest in theworld, with rates increasing from 1.57 in 1993 to 2.21in 2002 but varying across the predominantly Asianethnicities (K. B. L. Tan, Tan, & Yeo, 2008). On thebasis of a 10-year average from 1993 to 2002, the ratesof clefting in Singapore are 2.00 in Chinese individuals,1.87 in Malay individuals, 1.26 in Indian individuals,and 1.16 in other ethnic groups (K. B. L. Tan et al., 2008).

Cognitive and Learning Difficultiesin Children With CLP

Monolingual infants, toddlers, and children withCLP are frequently found to have below-average scoreson verbal IQ tests (Conrad, Richman,Nopoulos,&Dailey,2009; Kuehn & Moller, 2000), even though a majority ofchildren with CLP perform within the average range ofoverall intelligence (Broder, Richman, & Matheson,1998; Richman & Nopoulos, 2009). This higher risk ofdepressed verbal performance and verbal mediationthereby place individuals with CLP to be at a greaterrisk of linguistic and learning disability than the generalpopulation (Broder et al., 1998; Conrad et al., 2009;Eliason & Richman, 1990; Jocelyn, Penko, & Rode,1996; Nation, 1970; Richman et al., 1988). In a study byBroder et al. (1998), 46% of the 6- to 18-year-olds withCLP were diagnosed with a learning disability, 47% haddisrupted educational progress, and 27% had repeated atleast a grade in school. As such, high learning disabilityrates between 25% and 80% identified in monolingualschool-age children with CLP illustrate that languagefunctions and psychosocial development may also be im-pacted in adulthood (Broder et al., 1998; Buckenberger,1990; Collett, Stott-Miller, et al., 2010; Richman &Eliason, 1986; Richman & Ryan, 2003).

Elevated learning disability rates may also explainthe high prevalence of disability on reading and reading-related tasks in school-age children with CLP, rang-ing from 17% to 61% (Richman et al., 1988, Richman,

Wilgenbusch, & Hall, 2005) compared with general pop-ulation rates of 5%–15% (Chapman, 2011; Collett, Stott-Miller, et al., 2010; Richman & Eliason, 1984; Richmanet al., 2005). In a recent study by Collett, Stott-Miller,et al. (2010), 42 children with CLP between 5 and7 years of age scored significantly lower than theirpeers with typical development (TD) on basic reading,phonological memory, and reading fluency. In the non-CLP and TD population, studies have documented thatreading achievement is dependent on appropriate cogni-tive, learning, and language skills (Scarborough, 2005;Wise, Sevcik, Morris, Lovett, & Wolf, 2007). ChildrenwithCLPwould be disadvantaged academically becauseof their higher prevalence of cognitive and language def-icits (Collett, Stott-Miller, et al., 2010; Young, Purcell, &Ballard, 2010), thereby placed at risk for ongoing lan-guage delays and memory difficulties.

Reasons for the cognitive and learning difficultiesdocumented in the monolingual CLP population includecortical auditory dysfunction (Čeponienė et al., 1999),verbal expressive delay (Conrad et al., 2009; Kuehn &Moller, 2000;Richman&Eliason, 1986), global languagedelay (Eliason & Richman, 1990), hearing (Richman& Eliason, 2001), poor neuropsychological function-ing (Richman, 1995), and aberrant brain development(Conrad et al., 2010). In the general and atypical (e.g.,dyslexia, specific language impairment) populations, re-search studies have implicated underlying cognitive pro-cesses such as workingmemory (WM) to affect languagedevelopment, vocabulary acquisition, and higher orderreasoning (Gathercole & Baddeley, 1989); however, inthe CLP population, studies in this area are limitedand undefined with mixed findings (Collett, Leroux, &Speltz, 2010; Collett, Stott-Miller, et al., 2010; Eliason& Richman, 1990; Maenpaa, Laasonen, Haapanen,Pulkkinen, & Virsu, 2008; Richman & Ryan, 2003). Assuch, it is still not clear as to whether the memory pro-cesses linked to the learning, linguistic, and educationaldifficulties found in the CLP population are global (bothverbal and visuospatial STM and WM), domain-specific(exclusively verbal or visuospatial), or component-specific(either STM or WM).

Memory Skills in Children With CLPStudies investigating the STM abilities of monolin-

gual children with CLP have used models of develop-mental dyslexia and neuropsychology to examine avariety of cognitive processes and their relationships toreading (Richman & Ryan, 2003; Richman et al., 2005).From a study sample of 154 childrenwith CLP, Richmanand Ryan (2003) documented 23% of children to haveverbal STM deficits, in conjunction with 30%–40% dis-playing readingdisabilities (Conrad et al., 2009;Richman&Ryan, 2003). Consequently, Richman et al. (2005) studied

Young et al.: Language and Memory in CLP 1315

the relationship between verbal and visual STM andreading disorders in 48 consecutive children with CLP.They found these 7- to 9-year-old children to performbet-ter with verbal information, with 65% of the childrenhaving the greatest deficit in visual STM, which was sig-nificantly correlated to reading disorders. The findingsof Richman and colleagues (Richman & Ryan, 2003;Richman et al., 2005) are supported by other studies doc-umenting that 3- to 8-year-old children with CLP showsignificant delays in visual STM (Smith & McWilliams,1968), together with difficulties in associative reasoningand categorization (Eliason & Richman, 1990).

Eliason and Richman (1990) employed the AuditoryAssociation Test (Kirk, McCarthy, & Kirk, 1968) on 654- to 6-year-old children with CLP and found them tohave an average verbal memory span but delays in ver-bal mediation compared with their peers with TD. Be-sides domain-specific memory processes, similarcognitive studies investigating children with CLP havereported impaired performance of cross-modal memorymeasures (e.g., visual-motor sequential, auditory-vocalautomatic, audiovisual sequential; Eliason & Richman,1990;Maenpaa et al., 2008). Thus, to eliminate the influ-ence of intersensory memory measures, we selected theWM model proposed by Baddeley and Hitch (1974) asour basis to profile the individual verbal and visuo-spatial memory abilities of children with CLP.

WM ModelThe WM model is a multicomponent system in-

volved in the temporary storage (i.e., STM) and simulta-neous manipulation (i.e., WM) of information assumedto be required for a wide range of complex cognitive ac-tivities (Gathercole, Willis, & Baddeley, 1991). In chil-dren, WM components are in place by 4 years of age,with WM capacity increasing steadily with age between4 and 14 years (Alloway, Gathercole, & Pickering, 2006).Within this model, attention and higher level processingare coordinated by the central executive, and verbalSTM and visuospatial STM support verbal WM andvisuospatial WM, respectively (Archibald &Gathercole,2006; Baddeley & Hitch, 1974). In language develop-ment, the phonological loop (measured by tests such asnonword repetition) has been strongly correlated withreceptive vocabulary knowledge, grammar, and second-language learning (Baird, Dworzynski, Slonims, &Simonoff, 2010; Messer, Leseman, Boom, & Mayo,2010), which in turn has been shown to highly predictmathematical performance (Kyttälä,Aunio,&Hautamäki,2010). Thus, limited verbal WM capacity may reflectweak linguistic representation (Bishop, 2000), therebyhaving negative effects in language learning and func-tioning (Montgomery, Magimairaj, & Finney, 2010;Summers, Bohman, Gillam, Peña, & Bedore, 2010).

For bilingual children, language knowledge may affectthe accurate processing and retrieval in their nondomi-nant language (Juhasz, 2005; Montgomery et al., 2010;Summers et al., 2010).

Likewise, the visuospatial sketchpad is crucial forlearning, as it is used to actively manipulate nonverbalinformation throughmaintaining attention in the visualor spatial modality, and it plays a role in the recognitionof letters and words in reading (Gathercole, 2006). As anatural trajectory in childhood, children with TD havebeen documented to rely increasingly on verbal pro-cessing strategies for visually presented information(Dehn, 2008). Thus, a better understanding of the rolesplayed by both verbal and visuospatial WM could beimportant for planning compensatory domain-specificand/or domain-general interventions for children withCLP, given thatWMunderliesmany aspects of academiclearning (Dehn, 2008).

Context of SingaporeSingapore is a multicultural country, wherebymulti-

lingualism is the norm. The official languages spoken areEnglish, Mandarin, Malay, and Tamil, with English asthe main medium of education, public administration,commerce, science and technology, and internationalrelations (Ministry of Education Singapore, 2008). InSingapore, 74.1% of the population are Chinese, withMalay individuals composing 13.4% of the population,Indian individuals composing 9.2% of the population,and other ethnic groups composing 3.3% of the popula-tion (Singapore Department of Statistics, 2010). TheChinese cohort was chosen for our study because it hadthe highest rate of clefting in Singapore, and it repre-sented the majority racial group. In addition, the pre-school period offered us an early opportunity to studywhen children first developed proficiencies in their orallanguage and cognitive foundations for learning, specif-ically WM. For this reason, we chose to evaluate theseskills to ascertain whether Singaporean preschool chil-dren were adequately prepared for primary school.

In 1979, the Singapore government mandated thebilingual education policy for all children attending for-mal schooling (Dixon, 2004). Itwas therefore compulsoryfor children to learn English in school, together with oneother official language as a second-language subject. Forthe Chinese population, this language policy resulted inhouseholds slowly shifting from predominantly usingChinese dialects (e.g., Hokkien, Teochew) to mainlyMandarin and English dialects (which they used withdiffering fluency across a lectal continuum; Dixon, 2004).As a result of this language shift, a high degree of multi-lingualism and linguistic tolerance resulted (Gupta,Brebner, & Chandler Yeo, 1998). Hence, even thoughSingapore Standard English is the official language of

1316 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1314–1328 • October 2012

education in Singapore, children in Singapore frequentlyenter preschool with a colloquial variety of English(Singapore Colloquial English) or Mandarin as theirmain language (Gupta, 1989). As such, Singaporean pre-school children may exhibit vocabulary and languagedifferences as an extension of reduced exposure to Stan-dard Singapore English. In Singapore, the traditionalpreschool curriculum emphasizes an academic focus toprepare children for the rigorous educational demandsof Primary One (Ministry of Education Singapore,2008). Preschool children from 3 years of age attendingpreschool are taught in English, and they are given 25%of their instruction time in their second language (Dixon,2004). Ensuring children with CLP have adequate foun-dational skills in English, as well as adequate learningand cognitive skills, is necessary to provide these chil-dren with the best chance of academic success.

Purpose of the StudyWith regard to the present study, it seems likely

that the high prevalence of language and learning dis-abilities in children with CLP (Kuehn & Moller, 2000;Richman et al., 2005), including those in Singapore(Young et al., 2010), could be attributed to verbal and/orvisuospatial STM and/or WM difficulties. Bilingual chil-dren learn two phonotactic systems as well as two lexical,two phonetic, and two syntactic systems, thereby placingdifferent demands on their STM, WM, and attentionalsystems (Summers et al., 2010). Bilingualismcan influencelanguage development because of the extensive code-mixing of the features in both languages, which couldalso be phonological, morphosyntactic, or pragmatic(Genesee, 2009). Reduced exposure, input, and frequencyof both languagesmay impair a bilingual child’s ability toacquire working knowledge of both languages, makingbilingual children more vulnerable, as they may showlags in language acquisition from a lack of adequate vo-cabulary in one or both languages to express themselvesfully in each language (Genesee, 2009; Nicoladis, Song, &Marentette, 2012). This study explores the verbal andvisuospatial memory abilities of Singaporean childrenwith and without CLP who use two contrasting lan-guages: English and Mandarin.

To our knowledge, no studies have profiled themem-ory abilities of bilingual children with CLP. In addition,the likelihood that a bilingual Chinese Singaporeanchild with CLP with normal cognitive functioning willhave expressive language impairment is between 3.9and 12.7 times more likely than the general population(Young et al., 2010). Such findings suggest that the po-tential aetiologies of persistent language difficulties,specifically verbal and visuospatial memory abilities,need to be investigated further. For this reason, theaims of this studywere twofold: (a) to test the hypothesis

that children with CLP would perform poorer thanchildren with TD on receptive vocabulary performancein English and Mandarin, as well as verbal and visuo-spatialmemorymeasures, and (b) to examine the degreeto which receptive vocabulary scores in English andMandarin are correlated with performance on verbaland visuospatial memory measures.

MethodParticipants

The number of participants required for both thestudy and comparison groups was established from pub-lished studies by Brebner (2002) and Young et al. (2010).The figures were based on the assumption that the pro-portion of Chinese Singaporean preschoolers with TD atrisk of language impairment was 10% (Brebner, 2002),and the corresponding proportion in the Chinese Singa-porean preschoolers with CLP was 33% (Young et al.,2010). A minimum sample size of 90 (45 per group)was required, on the basis of a two-sided McNemar’stest with a 5% Type I error and 80% power, on the basisof an anticipated medium effect size of Cohen’s d = 0.5(Machin, Campbell, Fayers, & Pinol, 1997).

We recruited a consecutive sample of 86 preschoolchildren with CLP and 100 preschool children with TDbetween June 2008 and June 2009. Participants withCLP were between the ages of 3;11 (years;months) and6;10 (mean age = 5;6, SD = 0.918), and participants withTD were between the ages of 3;8 and 6;5 (mean age =4;11, SD = 0.815).

To recruit sufficient numbers in this study and tominimize the variables associated with different lan-guage backgrounds, we limited our study to native Chi-nese Singaporean participants who spoke English andMandarin (74.1% of the Singapore population; SingaporeDepartment of Statistics, 2010). Information pertainingto residential categories and language dominance wasgathered from parent report. Residential categories givean indication of socioeconomic status, as it is linked to one’smonthly combined household income ceiling (SingaporeDepartment of Statistics, 2010). Childrenwere allocatedto English as dominant language (EL1) and Mandarinas dominant language (ML1) groups on the basis of par-ent report. In the parent report, language dominanceclassification was allocated on factors identified as im-portant in previous research: (a) Proficiency of the child’sfirst language ranked higher than his or her second lan-guage, (b) the child’s first language was spoken mostof the time by his or her parents, and (c) language towhich the child received the highest amount of exposure(Li, Sepanski, & Zhao, 2006; S. H. Tan, 2010).

All participants were in mainstream preschoolsand were current clients of the Singapore National


Healthcare Programme, whereby their development ismonitored by a pediatrician annually from birth to6 years of age. None of the participants had been diag-nosed with any syndromes or neurological disorders,and they were not receiving specialist services providedfor children with developmental delay. All participantshad normal or corrected vision at the time of testing,as they had all undergone compulsory vision screeningat their preschools as part of the Health Promotion Boardof Singapore’s National Myopia Prevention Programme.Children who failed their hearing screening were ex-cluded from the analysis.

Children with CLP. Participants with CLP (CLPgroup) were recruited from the Kandang Kerbau Cleftand Craniofacial Centre (KKCCRC) within KKHospitalin Singapore, which is the national referral center dedi-cated to cleft and craniofacial treatment in Singaporeand Southeast Asia (Young et al., 2010). As part of theroutine surgical protocol for CLP-staged repair, theKKCCRC Cleft Palate Team performs lip closure and/orrhinoplasty at 3 months and performs palate closure at9 months (Yi, Yeow, & Lee, 1999; Young et al., 2010). Inaddition, children with CLP follow a standard timelinewith regard to their speech and language assessment,and they receive therapy from 6 months of age and arereviewed every 6–12 months until they are 18 years ofage. This way, children with speech, resonance, or lan-guage difficulties are seen for blocks of therapy, on aneeds-led basis. A total of 93 eligible children with CLPmet the inclusion criteria in the KKCCRC database andwere invited to participate in the research study. Of these,parents of 86 children with CLP (92%) consented to par-ticipate in the study. Following exclusion of childrenwithCLP who failed their hearing screening (n = 16), the CLPsample (n = 70) included 15 participants with cleft liponly, 15 participants with unilateral cleft lip and palate,five participants with bilateral cleft lip and palate, and35 participants with cleft palate only. See Table 1 for fur-ther details of the CLP group’s characteristics.

Children with TD. Participants from the TD group(n = 100) were typically developing, according to bothparent and teacher reports. Children with TD wererecruited from the community through advertisementsplaced in public and private preschools throughout Sin-gapore. Interested parents were then invited to contactthe study team directly to arrange for an appointment tohave their child participate in the research study. Fol-lowing exclusion of children who failed their hearingscreening (n = 1) and who refused hearing screening(n = 2), a total of 97 children with TD were recruited.

Characteristics of all 167 participants from bothgroupswere compared (see Table 2).Mean agewas signif-icantlyhigher for theCLPgroup, t(167) = 4.29,p< .001; assuch, age was entered as a covariate in subsequent sta-tistical analyses. There was also a significant differencebetween both groups in the use of either EL1 or ML1,with the CLP group having more participants who spokeMandarin, c2(1,N= 167) = 10.48,p≤ .001. Sex ratios andresidential categories were not significantly differentbetween the groups, c2(1, N = 167) = 2.70, p = .100; c2(2,N = 167) = 1.74, p = .419, respectively. The significantdemographic variables (age and dominant language)were therefore taken into account by adjusting statisti-cal analyses when both groups were compared (see theData Analysis section).

ProcedureThe Kandang Kerbau Hospital Institutional Re-

view Board in Singapore and the University of SydneyHuman Research Ethics Committee in Australia ap-proved the procedures. Following parental consent andchild assent (only for the children who were 6 years ofage), each participant attended a single 1-hr session witha research assistant in a quiet room to complete the ex-perimental protocol. The research assistant was a nativespeaker of Singapore English and Mandarin. The proto-col included (a) audiometric screening, (b) articulation

Table 1. Features of nonsyndromic cleft lip and/or palate (CLP) participants for cleft type, language dominance, hearingstatus, and vision status.

Type of CLP

Total CLPparticipants(N = 70) EL1 ML1

Passedaudiometric

screen

Passedvisionscreen

Cleft lip only 15 11 4 15 15Unilateral cleft lip and palate 15 10 5 15 15Bilateral cleft lip and palate 5 3 2 5 5Cleft palate only 35 25 10 35 35

Total (% of total CLP participants) 70 (100.0) 49 (70.0) 21 (30.0) 70 (100.0) 70 (100.0)

Note. Values represent the number of participants; numbers in parentheses represent percentages. EL1 = English as dominantlanguage; ML1 = Mandarin as dominant language.


assessment using the Diagnostic Evaluation of Artic-ulation and Phonology (DEAP; Dodd, Zhu, Crosbie,Holm, & Ozanne, 2002) and the Cleft Audit Protocol forSpeech (CAPS; Harding, Harland, & Razzell, 1997), (c) theEnglish and Mandarin versions of the SingaporeBilingual Vocabulary Test (SBVT; Rickard Liow & Sze,2007), and (d) four subtests from theAutomatedWorkingMemory Assessment (AWMA; Alloway, 2007).

Audiometric screening.A 10-min audiometric screen-ing was performed using a Madsen Micromate 304 por-table screening audiometer at the pure-tone frequenciesof 500, 1000, 2000, and 4000Hz to rule out sensorineuralhearing loss. Using the American Speech-Language-Hearing Association’s (1997) guidelines, a child partici-pant was classified as having failed the audiometricscreening if his or her individual pure-tone averageexceeded 20 dBHL in the poorer ear. All children partic-ipated in the audiometric screening except two childrenfrom the TD group who refused testing.

Articulation assessment. Each participant’s single-word articulation was assessed using the ArticulationSingle-Word Production subtest from the DEAP (Doddet al., 2002). The DEAP and CAPS (Harding et al., 1997)were both conducted to gain a comprehensive picture ofevery participant’s articulatory abilities in words andsentences. This was necessary, as Nonword Recall, Lis-tening Recall (processing and memory), and SpatialSpan (processing) required the participant to giveresponses verbally. Participants were therefore not pe-nalized for articulatory errors in their verbal responsesshould those errors be identified in the DEAP and/or

CAPS. The DEAP is a battery designed to provide differ-ential diagnoses of speech disorders in children betweenthe ages of 3;0 and 8;11. In the Articulation Single-WordProduction subtest, participants were asked to name30 colored pictures that comprised target words consist-ing primarily of consonant–vowel–consonant syllableshapes (e.g., “pig”). The DEAP took approximately5 min to complete. Subsequently, standardized sen-tences designed to evaluate consonants in differentword positions were assessed using the CAPS. TheCAPS was chosen because it has been recognized as asuccinct perceptual speech protocol with good reliability(Sell et al., 2001). The research assistant gave the sen-tences verbally and concurrently presented colored pic-tures to facilitate sentence imitation. The CAPS tookapproximately 5 min to complete.

Receptive vocabulary assessment.The SBVTis a fully-computerized test for bilingual Singaporean children(Rickard Liow & Sze, 2007). Currently, it is the only re-ceptive language test standardized on Singaporean chil-dren between 5 and 7 years of age, and it is available inEnglish, Mandarin, and Malay. The SBVTwas adminis-tered first inEnglish and then inMandarin to provide anindex of each child’s competence in both languages. Inthe SBVT, participants were presented with four pic-tures on a computer screen and were asked to selectthe picture that best matched the word recorded by aSingaporean English–Mandarin female native speaker.The full test was graded for difficulty, and it comprised200 trials (100 different items per language) with forcedpicture choice (one out of four) in response to a spokenword auditorily presented over free-field Altec Lansingspeakers. Each correct answer was awarded 1 point.Testing was stopped when the participant failed onseven consecutive items. The SBVT took approximately20 min (10 min per language) to complete.

Memory assessment. Verbal and visuospatial STMand WM abilities were measured using the Englishversion of the AWMA (Alloway, 2007). The AWMAwasselected because it has an automated presentation andscoring procedure and because it is suitable for screen-ing individuals with significant WM difficulties fromearly childhood to adulthood. Currently, the AWMA,which is based on Baddeley and Hitch’s (1974) theory,is the only WM scale that distinguishes visuospatialWM from visuospatial STM (Dehn, 2008). As well, thistest has been standardized on a U.K. sample comprisingEnglish-dominant speakers from diverse ethnic groups(e.g., Bangladesh, China, and Africa;1 Alloway, 2007).

Table 2. Features of CLP and typical development (TD) groups for sex,age, language dominance, and residential category.

Participant characteristicCLP group(n = 70)

TD group(n = 97)

Sex (%)Male 32 (45.7) 58 (59.8)Female 38 (54.3) 39 (40.2)

Mean age in years (SD)* 5.54 (0.92) 4.97 (0.80)Dominant language (%)*

English 49 (70.0) 88 (90.7)Mandarin 21 (30.0) 9 (9.3)

Residential categories (%)Small HDB flat 8 (11.4) 11 (11.3)Large HDB flat 44 (62.9) 52 (53.6)Private housing 18 (25.7) 34 (35.1)

Note. Unless otherwise indicated, values represent the number ofparticipants; numbers in parentheses represent percentages or standarddeviations (see first column). HDB = Housing and Development Board(Singapore public apartment housing).

*p < .05.

1TheMandarin version of the AWMAwas not available when data collectionfor this research study commenced. We were also not able to compare ourscores with the AWMA norms, as we discovered an error in the program-ming of the AWMA software. No normative data using the correct scoringhave yet been made available.


Four subtests were chosen in this study: two mea-suring verbal STM and WM (i.e., Nonword Recall andListening Recall, respectively) and the other two mea-suring visuospatial STM and WM (i.e., Dot Matrix andSpatial Span, respectively). The subtests were pre-sented via a computer, together with audio-recordingsof a native British adult female speaker supplied withthe published test and delivered via Altec Lansingfree-field speakers. Every subtest was explained toeach participant individually, and an opportunity topractice three trial items systematically was given to en-sure that each subtest was understood prior to formaltesting.

Each subtest consisted of six blocks, with each blockbeing a different level of difficulty. The first block (easi-est level) consisted of six trials, and the number of itemsto be recalled in these trials increased by one in the nextblock. The criterion for progressing to the next block wasthe correct recall of four items within a block (either con-secutively or nonconsecutively). The subtest was discon-tinued when three incorrect recalls were made within ablock. Scores for each subtest were computerized, withthe total score for each subtest based on the total num-ber of correct responses plus the assumed correct itemsthatwere skipped.Test administrationwas in accordanceto the AWMA instructions and took approximately20 min to administer.

Verbal STM. The Nonword Recall subtest was usedto assess the verbal STM abilities and the temporary re-tention of verbalmaterial through the phonological loop.Each participant heard a voice-recorded sequence ofmonosyllabic nonwords (e.g., “jod bim”) presented at arate of one nonword per second, with the computerscreen remaining blank. The participant was encour-aged by the research assistant to repeat each nonwordwith the correct order of phonemes, with each sequencein the correct serial order. The accuracy of sequence andarticulation was taken into account during live scoring.The participant was not penalized for any articulatoryerrors noted from the DEAP and CAPS assessments.Each correct response for each nonword or sequence ofnonwords scored 1 point.

Given that the AWMA had been standardized withthe British–English population, our scoring system wasadapted to be more culturally and linguistically ap-propriate. Our scoring system allowed us to obtain amore sensitive and relevant picture of our participants’performances by considering the characteristic pronun-ciation of both Singapore Standard English and Singa-pore Colloquial English, thereby not unfairly penalizingtheir productions. This type of scoring had previouslybeen reported by Dollaghan, Biber, and Campbell(1995), who did not treat dialectal alterations of pho-nemes typical of Black English as errors when scoring

nonwords, and by Gutiérrez-Clellen and Simon-Cereijido(2010), who did not penalize Spanish-influenced errorswhen scoring English nonwords spoken by bilingualSpanish–English children. For these reasons, we tookinto account responses in both Singapore English var-iants when scoring each nonword.

Verbal WM. The Listening Recall task was adminis-tered to assess verbal and executive WM, measuredthrough the storage of verbal material with a secondaryprocessing task (Dehn, 2008). Each participant waspresented with a series of spoken sentences while thecomputer screen remained blank.For theprocessing com-ponent of Listening Recall, participants had to verify eachsentence by stating whether it was “true” or “false” (pro-cessing component). Each correct response scored1 point for processing. For the memory component ofListening Recall, participants had to recall the lastword for each sentence or sequence of sentences. Eachcorrect last word or a sequence of last words scored1 point. The first block started with one sentence and in-creased to a block of six sentences.

Visuospatial STM. This task assessed the visuospa-tial STM storage of visuospatial information using theDot Matrix subtest. Each participant was shown theposition of a red dot (exposed for 2 s) in a series of 4 ×4 matrices and had to recall this position by tappingthe appropriate squares on the computer screen. Theparticipant had to recall the dot(s) in the correct orderto receive a correct score of 1 point for each trial. Thetest commenced with a block of one dot and increasedto a block of nine dots.

VisuospatialWM.TheSpatial Span taskwas used tomeasure the visuospatial WM capacity of the partici-pants. The participant viewed a picture of two shapeson the computer screen, in which the shape on theright had a red dot on it. For the processing component,the participant had to identify whether the shape on theright was the “same” (normal orientation) or “opposite”(mirror image) to the shape on the left. One point wouldbe given for the correct identification of the orientationof the shape. Furthermore, the shape with the red dotcould also be rotated. Next, the participant had to recallthe location of the red dot on the shape in sequence bypointing to a picture with three compass points shownon the computer screen. The participant would receivea memory score for correctly identifying the dot(s) in se-quence. The test began with a block of one set of shapesand increased to a block of seven sets of shapes.

The responses to the DEAP, CAPS, SBVT (Englishand Mandarin), and AWMA were audio- and video-recorded with a Sony HDR-HC9E camcorder andattached Audio-Technica ATR3s lavalier microphone,maintained at a mouth-to-microphone distance of 10 cm.All responses were double-checked by the principal


investigator, and responses to the Nonword Recall,DEAP, and CAPS were phonetically transcribed. Subse-quently, recordings were randomized for intra- andinterrater reliability analyses of the participants’ ar-ticulatory responses for the Nonword Recall, DEAP,and CAPS.

Intrarater reliability. Twenty percent (10% for chil-dren with CLP and 10% for children with TD) of therecorded Nonword Recall, DEAP, and CAPS data wererandomly selected. Data were rescored by the princi-pal investigator (a speech-language pathologist with12 years of experience in craniofacial speech-languagepathology and cleft speech transcription, and who wasa native speaker of Singapore English and Mandarin).The percentage of exact point-to-point agreement was92.7% (Nonword Recall), 94.2% (DEAP), and 95.3%(CAPS)—calculated by dividing the number of agree-ments by the total number of agreements and disagree-ments. This high level of agreement is similar to findingsalluded to in Cordes (1994), which cites more than 80%agreement as moderate-to-excellent reliability.

Interrater reliability.Twenty percent of the recordeddata were retranscribed by a speech-language patholo-gist (who was not involved in the study) with 5 years ofexperience in craniofacial speech-language pathologyand cleft speech transcription, and who was a nativespeaker of Singapore English and Mandarin. The speech-language pathologist received training on the dialectaldifferences for Singaporean speakers and how to scoreeach verbal item on the basis of either a dialectal differ-ence or a consistent articulation error. The percentage ofexact point-to-point agreement was 88.7% (NonwordRecall), 91.4% (DEAP), and 94.7% (CAPS).

Data analysis. The primary independent variablewas CLP status. In the absence of normative data forthe key dependent variables, children with CLP (CLPgroup) were compared with a group of children withTD (TD group). Descriptive analyses (frequencies, means,and standard deviations) were used to contrast thedemographic variables (e.g., age, sex) and the eightdependent variables (English vocabulary, Mandarin vo-cabulary,NonwordRecall, ListeningRecall [processing],Listening Recall [memory], Dot Matrix, Spatial Span[processing], and Spatial Span [memory]) of the CLPand TD groups. The distribution of scores was sig-nificantly nonnormal for most continuous variables.Mandarin vocabulary was normally distributed, andage was very mildly platykurtic.

Preliminary analyses suggested that both age anddominant language (EL1 or ML1) were potentially con-founding variables. Age was controlled by entering it asa covariate, as the mean age was significantly differentbetween the CLP and TD groups, and as it has also beenknown to have a considerable effect on vocabulary size

and memory in children (Gathercole & Baddeley, 1989;Gathercole, Pickering, Ambridge, & Wearing, 2004).Language was entered as a grouping variable with twolevels (EL1 or ML1) in combination with either CLP orTD groups, thereby producing four participant sub-groups (CLP–EL1, CLP–ML1, TD–EL1, TD–ML1) forcomparison. Data were analyzed by planned contrastanalyses of covariance (ANCOVAs) comparing EL1group with ML1 group, CLP–EL1 with TD–EL1, andCLP–ML1 with TD–ML1. This method was chosen inpreference to standard 2 × 2 factorial ANCOVAs becauseit directly made the comparisons of interest while keep-ing group sizes for those comparisons adequate to en-sure robustness in the face of nonnormal dependentvariable distributions. ANCOVA is widely held to be ro-bust against nonnormality of its dependent variable aslong as the covariate is normal or close to normal, andgroup sizes are adequate (Field, 2009, p. 42), as theyare here. In addition, ANCOVA is able to deal with thenonnormal distribution shapes of most of our dependentvariables, given the limits of the small numbers of differ-ent subgroup types after dominant language was takeninto account.

Finally, nonparametric Spearman correlationalanalysis was used to explore findings revealed by theANCOVA.2 Unlike analysis of variance or ANCOVA,Pearson correlations are affected by nonnormal distri-butions. Initially, we had also planned to compare testperformances within the CLP group, but the constraintof smaller sample sizes within the four CLP subtypesafter languagewas controlled for (e.g., twoML1 childrenwith bilateral cleft lip and palate, 25 EL1 children withcleft palate only; see Table 1), in conjunction with thenonnormality of the dependent variables, preventedthis.

ResultsDescriptive statistics for all vocabulary andmemory

assessments are presented in Table 3, with only the sig-nificant comparisons summarized in the text.

Receptive Vocabulary AssessmentThe EL1 group performed significantly higher than

the ML1 group for English SBVT, F(1, 162) = 57.10,p< .001, partial h2 = .51. Similarly, theML1 group scoredsignificantly higher than the EL1 group for MandarinSBVT, F(1, 162) = 29.18, p < .001, partial h2 = .39.

2The nonnormality of most continuous variables rendered multiple regressionanalysis nonviable.


There were no significant group differences betweenchildren with CLP and TD.

Memory AssessmentThe EL1 group performed significantly higher than

the ML1 group for the processing component of Listen-ing Recall (verbal WM), F(1, 162) = 5.18, p = .02, partialh2 = .18. There were no significant group differences be-tween children with CLP and TD.

Correlation AnalysesSpearman correlation analyses among all vocabu-

lary and memory scores for all participants with CLPand TD (N = 167) are presented in Table 4. These anal-yses have been split on the basis of dominant language(EL1 or ML1) for both CLP and TD groups.

EL1. For the CLP–EL1 group, the correlations be-tween English vocabulary and all memory measureswere positive and moderate-to-strong (Asuero, Sayago,& González, 2006; all one-tailed ps < .01). This findingsuggests there is a relationship between verbal andvisuospatial memory measures and English receptivevocabulary for children with CLP. Specifically, the pro-cessing and memory components of Listening Recall(verbal WM) showed the strongest association with En-glish vocabulary (r = .621, p < .001; r = .591, p < .001, re-spectively). The processing aspects of the ListeningRecall and Spatial Spanmeasures were also very highlycorrelated with their respective memory tasks, Listen-ing Recall (memory; r = .957, p < .001) and SpatialSpan (memory; r = .916, p < .001), respectively.

For the TD–EL1 group, the correlations betweenEnglish vocabulary and all memory measures werealso positive and moderate-to-strong. The processingand memory components of Spatial Span (visuospatialWM) showed the strongest association with English vo-cabulary (r= .655,p< .001; r= .634,p< .001, respectively).However, unlike the CLP–EL1 group, the Mandarin vo-cabulary ability of the TD–EL1 group also showed a sig-nificant positive correlation with all measures exceptNonword Recall (r = .008, p = .942). Consistent withthe TD–EL1 group’s performance, the processing aspectsof the Listening Recall and Spatial Span measures werealso very highly correlated with their correspond-ing memory tasks (r = .946, p < .001; r = .944, p < .001,respectively).

ML1. For the CLP–ML1 group, correlations be-tween English vocabulary and all memory measures (ex-cept Dot Matrix) were positive and moderate-to-strong(all one-tailed ps < .01). The processing aspects of the Lis-tening Recall and Spatial Span measures were also veryhighly correlated with their respective memory tasks,Listening Recall (memory; r = .876, p < .001) and SpatialSpan (memory; r = .985, p < .001), respectively.

For the TD–ML1 group, comprising fewer partici-pants,Mandarinvocabularywaspositivelyandsignificantlycorrelated with all measures except Nonword Recall,which reached only borderline significance (r = .316,p = .061). Correlations were positive and high betweenthe processing and memory aspect of Listening Recall(verbal WM; r = .636, p < .001; r = .587, p = .001, respec-tively). A moderate association was also found betweenDot Matrix (visuospatial STM; r = .402, p = .028) andthe processing and memory aspect of Spatial Span

Table 3. Adjusted means (using age as a covariate) of vocabulary and memory assessment scores for all participants (N = 167).

Measure

Group EL1 ML1

EL1(n = 137)

ML1(n = 30)

Effectsize F (1, 162)

CLP(n = 49)

TD(n = 88)


CLP(n = 21)

TD(n = 9)


VocabularyEnglish SBVT 54.14 32.61 0.51 57.10 51.97 55.35 0.12 2.40 30.45 37.68 0.12 2.23Mandarin SBVT 31.84 49.16 0.39 29.18 30.60 32.53 0.05 0.47 48.42 50.89 0.03 0.16

Verbal memoryNWR 5.62 4.52 0.08 1.07 5.69 5.59 0.01 0.03 3.91 5.95 0.12 2.51LR (p) 10.08 6.40 0.18 5.18 9.50 10.41 0.06 0.63 5.72 7.98 0.07 0.79LR (m) 4.53 3.16 0.15 3.49 4.08 4.78 0.11 1.9 2.94 3.66 0.05 0.41

Visuospatial memoryDM 15.61 14.83 0.03 0.19 14.93 16.00 0.11 2.05 14.45 15.71 0.06 0.58SS (p) 20.44 17.73 0.05 0.39 21.07 20.08 0.02 0.08 17.34 18.66 0.01 0.03SS (m) 9.15 7.88 0.08 1.04 9.27 9.08 0.02 0.04 7.69 8.33 0.02 0.09

Note. Scores in bold represent a significant difference (p < .001) between groups. SBVT = Singapore Bilingual Vocabulary Test; NWR = Nonword Recall;LR (p) = Listening Recall (processing); LR (m) = Listening Recall (memory); DM = Dot Matrix; SS (p) = Spatial Span (processing); SS (m) = Spatial Span(memory).


(visuospatial WM; r = .549, p = .002; r = .576, p < .001,respectively).

To summarize, although the correlation matricessuggested there are some differences in the pattern ofcorrelations for the children with CLP and those withTD, group comparisons controlling for age revealed nodifferences in performance between bilingual childrenwith CLP and bilingual children with TD.

DiscussionSchool-age monolingual children with CLP have

been reported to exhibit language and cognitive deficitsrelative to their peers with TD (Broder et al., 1998; Nash

et al., 2001; Richman & Eliason, 1984; Richman &Nopoulos, 2009). These deficits place them at an in-creased risk of learning difficulties, reading disabilities,and psychological maladjustment from childhood toadulthood (Endriga, Jordan, & Speltz, 2003; Richman& Lindgren, 1980). However, the underlying reasonsfor language deficits in the CLP population remain in-conclusive and varied (Kuehn & Moller, 2000; Priester& Goorhuis-Brouwer, 2008; Richman & Eliason, 2001;Young et al., 2010), and it is not clear how difficultiescan be identified in bilingual preschool children. In thislarge-scale study of 3- to 6-year-olds, we investigatedwhether any verbal and visuospatial memory deficitsmight be related to a higher prevalence of language diffi-culties in preschool children with CLP. First, we tested

Table 4. Correlation coefficients between all vocabulary and AWMA memory measures for all participants (N = 167).

Measure Group 1 2 3 4 5 6 7 8

EL11. English SBVT CLP .272 .461** .621** .591** .651** .660** .574**

TD .307** .406** .507** .453** .522** .655** .634**2. Mandarin SBVT CLP .156 .231 .202 .327* .318* .270

TD .008 .319** .287** .380** .351** .363**3. NWR CLP .355* .263 .375* .386** .354*

TD .321** .270* .318** .322** .332**4. LR (p) CLP .957** .507** .551** .585**

TD .946** .443** .525** .541**5. LR (m) CLP .428** .469** .507**

TD .399** .532** .537**6. DM CLP .805** .732**

TD .604** .665**7. SS (p) CLP .916**

TD .944**8. SS (m) CLP

TD

ML11. English SBVT CLP .598** .532* .725* .623* .423 .600** .612**

TD .736* .136 .426 .568 .523 .551 .6082. Mandarin SBVT CLP .316 .782** .721** .505* .604** .551**

TD .203 .814** .792* .597 .690* .815**3. NWR CLP .478* .389 .141 .440* .484*

TD .223 .392 .026 .194 .2384. LR (p) CLP .876** .555** .633** .621**

TD .900** .641 .606 .692*5. LR (m) CLP .586** .468* .466*

TD .614 .617 .6576. DM CLP .670** .670**

TD .880** .860**7. SS (p) CLP .985**

TD .949**8. SS (m) CLP

TD

Note. AWMA = Automated Working Memory Assessment.

*p < .05 (one-tailed). **p < .01 (one-tailed).


whether bilingual children with CLP performed morepoorly thanbilingual childrenwithTDon receptive vocab-ulary in English and Mandarin as well as verbal andvisuospatial memory measures. Second, we analyzedthe degree to which receptive vocabulary scores in En-glish and Mandarin were correlated with performanceon verbal and visuospatial STM and WM tasks.

Receptive VocabularyAs expected, children from both the EL1 and ML1

groups performed best in the receptive vocabulary testversion aligned with their dominant language (i.e.,English for EL1 and Mandarin for ML1). Vocabularyperformance appeared to be related to language useand exposure (Gutiérrez-Clellen & Simon-Cereijido,2010), highlighting the importance of assessing childrenin their dominant language. As well, the SBVT (RickardLiow&Sze, 2007) appeared to be sensitive in classifyingbilingual children’s first learned language and clinicaldifferentiation of language dominance when both lan-guages were tested.

Nevertheless, when the presence of CLP and lan-guage dominance was taken into account, no statisticaldifferences in vocabulary scores were noted between theCLP and TD groups. These findings support Eliason andRichman (1990), who found monolingual preschoolerswith CLP to have normal vocabulary development, aswell asCollett, Leroux, andSpeltz (2010),whodocumentedmonolingual children 5–7 years of age to show a nearequivalence of vocabulary scoreswhen comparedwith con-trols and within the average range relative to test norms.Thus, it would appear that vocabulary development doesnot differ in bilingual childrenwithCLP. This also suggeststhat although the vocabulary measures were sufficientlysensitive, they did not allow us to detect potential differ-ences in bilingual preschoolers with and without CLP.

Also, as we recruited a consecutive sample of partic-ipants with CLP with different dominant language pat-terns, we could not control the sample sizes for each ofthe CLP types. Research has documented mixed find-ings of childrenwithCLP to have language and cognitivedifferences on the basis of CLP type (Richman&Eliason,1984; Richman & Nopoulos, 2009). Hence, as the rela-tionship between cleft type and cognitive and linguisticskills is unclear, recruiting adequate sample sizes foreach of the CLP types may clarify these findings.

Verbal and Visuospatial MemoryAs a whole, English-dominant children from both

CLP and TD groups performed significantly better inverbal WM (processing), operationalized by ListeningRecall processing. This is an expected finding becauseListening Recall (processing) utilizes English stimuli,

and for a ML1 user, verbal WM may be affected by anincreasedmemory load on the phonological loop and cen-tral executive (Baddeley &Hitch, 1974), associated withprocessing phonological stimuli in one’s nondominantlanguage (Dehn, 2008; Gutiérrez-Clellen & Simon-Cereijido, 2010).

Specifically, we found strong positive relationshipsbetween English receptive vocabulary scores and allmeasures of verbal and visuospatial STM andWM. Con-sistent with this, performance on Nonword Recall hasbeen shown to predict English vocabulary developmentin some studies (Adams & Gathercole, 1995; Roy &Chiat, 2004). The moderate correlation (r = .41) betweenEnglish receptive vocabulary and Nonword Recall forour participants between 3 and 6 years of age was simi-lar to the correlations between the same measures forchildren with TD between 2 and 4 years of age (Adams& Gathercole, 1995; Roy & Chiat, 2004). These cor-relations between English receptive vocabulary andNonword Recall also suggest that verbal STM and lan-guage exposure play an important role in supportingEnglish vocabulary learning in preschool children.This has implications for children entering an educationsystem in which the medium of instruction is their non-dominant language.

On the other hand, Mandarin receptive vocabularyscores showedmuchweaker, although significant, corre-lations with all memorymeasures (with the exception ofNonword Recall; see below). The finding that receptivevocabulary is positively correlated with verbal andvisuospatial memory suggests that these information-processing resources underlying language-learningandmemory-development processes are shared (Summerset al., 2010). The stronger correlation of English vocabu-lary than Mandarin vocabulary with performance inNonword Recall, Listening Recall (processing and mem-ory), and Spatial Span (processing) tasksmay be relatedto the encoding, rehearsal, and manipulation of phono-logical representations of verbal responses (Dehn,2008). These findings raise the question of whethertrue estimates ofmemory abilities should be done specif-ically in one’s dominant language, thereby supporting abilingual approach to the evaluation of bilingual children.Administering theMandarin version of the AWMAwouldthus clarify this question.

Of interest, the only memory measure that was notcorrelated with Mandarin receptive vocabulary was themeasure of verbal STM (Nonword Recall). This suggeststhat the verbal skills required to perform NonwordRecall are language specific, reflecting the relationshipbetween language familiarity, vocabulary knowledge,verbal STMcapacity, and phonotactic information to cre-ate an accurate production of a nonword (Bowey, 2001;Messer et al., 2010; Stokes, Wong, Fletcher, & Leonard,2006; Thorn&Gathercole, 1999). A similar examplewas


illustrated with Turkish–Dutch children showing clearphonotactic knowledge on verbal STM in Turkish, sug-gesting sublexical knowledge in the dominant languageto support Nonword Recall (Messer et al., 2010). Thistrend was also noted for English–French children whowere significantly poorer at recalling French nonwordsthan French–English children (Thorn & Gathercole,1999). These results reinforce the view that superior vo-cabulary knowledge is related to higher acquisitionlevels of both words and nonwords in one’s dominantlanguage (Bowey, 2001; Thorn &Gathercole, 1999). Per-haps childrenwith a greater exposure to the tested dom-inant languagemay find it easier to draw analogies withthe phonological forms of real words in that language (inthe case of Nonword Recall; Gutiérrez-Clellen & Simon-Cereijido, 2010). This could have perhaps disadvantagedthe ML1 participants who were less able to use mor-phological or phonological cues from Mandarin whenprocessing nonword stimuli in an inherently differentlanguage and who could have relied on other types ofprocessing skills (English; Gutiérrez-Clellen & Simon-Cereijido, 2010; Messer et al., 2010; Zhu & Dodd, 2005).

In addition, we found that the Listening Recall pro-cessing and Spatial Span processing subtests were veryhighly correlated to Listening Recall memory and Spa-tial Span memory, respectively. This suggests that per-haps the skills needed for each WM test were stronglyinterrelated, questioning the need to score both the pro-cessing and memory components of the AWMA.

LimitationsAlthough the sample size of children with CLP in

the present study was large, the subgroups of partici-pants with different types of CLP after language wascontrolled for were too small for statistical comparisons(see Table 1). Also, only nine children (9.3%) from our TDgroup were ML1; hence, the results for this subgroupshould be interpreted conservatively. We acknowledgethat there was an absence of nonverbal IQ measure-ments for the participants and that statistical compari-sons of language exposure obtained from the parentreport between groups were not performed. As well,even though Mandarin receptive vocabulary was signif-icantly correlated with both WM measures and visuo-spatial STM, the correlations were low.

Future DirectionsFuture research may benefit from recruiting larger

samples across the different CLP subtypes to explorewhether differences exist depending on cleft type, sex,language dominance, hearing history, age group, andIQ performance. The assessment of bilingual childrenwith CLP should be delivered in both languages so as

to ensure that language dominance is not a confoundingfactor.Moreover, as vocabulary skill is a strong predictor ofearly literacy (Dixon, 2004; Vellutino, Fletcher, Snowling,& Scanlon, 2004), future research should encompass theanalysis of language-related academic domains (e.g.,reading, spelling, writing, mathematics). Further re-search exploring additional measures of linguistic abili-ties, such as early phonological awareness and otherpredictors of literacy skill development, is also needed.As WM was not different between groups, an investiga-tion of other possible causes for language and cognitivedeficits described in the literature (Conrad et al., 2009;Kuehn&Moller, 2000; Young et al., 2010) is still needed.This is because the reported deficits in monolingualschool-age childrenwithCLPmight becomemore obviousin older bilingual childrenwithCLPwhen the demands ofacademic work increase. Bilingual children with CLPwould then become especially vulnerable if the mediumof instruction was not their dominant language. Clearly,a longitudinal follow-up of bilingual children with CLP,frompreschool onward and using a broader range ofmea-sures in the school-age years, would verify whether theobserved similarities in cognitive-linguistic profiles be-tween CLP and TD groups remain.

SummaryIn conclusion, the results of this study suggest that

the performance of preschool bilingual children withCLP is comparable with TD children when matched forage. However, regardless of clinical diagnosis, childrenwhose first language is not English—the main mediumfor instruction in school—appear to be at greater risk forpoorer performance in English vocabulary and in verbalWM tests that utilize English stimuli. Although thiswould be expected in any population of preschoolers, asystematic longitudinal study of bilingual childrenwith CLP, beginning from preschool age and extendingthrough school age, is needed to ensure that perfor-mance is optimized in later years after the demands ofthe curriculum increase. This would facilitate the earlyidentification of bilingual children with CLP who dis-play language and cognitive difficulties in their lan-guage of education and ensure that they have the bestchance of solid educational achievement.

AcknowledgmentsThis study was supported by SingHealth Foundation

Grant SHF/FG350S/2007 and by funds from the Faculty Post-graduateFunding (2009–2010) and thePostgraduateResearchSupport Scheme (2008, 2010) from the University of Sydney(NewSouthWales, Australia).We thank all the childrenwho par-ticipated in this study. We also thank Karen Lee, Genevieve Ng,Melanie Chastan, Cecilia A. Chandra, and Vincent Yeow fortheir assistance with various aspects of the study.


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