Content uploaded by Rebecca Ward
Author content
All content in this area was uploaded by Rebecca Ward on Nov 15, 2023
Content may be subject to copyright.
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=ncny20
Child Neuropsychology
A Journal on Normal and Abnormal Development in Childhood and
Adolescence
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/ncny20
Predicting language outcomes in bilingual children
with Down syndrome
Rebecca Ward & Eirini Sanoudaki
To cite this article: Rebecca Ward & Eirini Sanoudaki (03 Nov 2023): Predicting language
outcomes in bilingual children with Down syndrome, Child Neuropsychology, DOI:
10.1080/09297049.2023.2275331
To link to this article: https://doi.org/10.1080/09297049.2023.2275331
© 2023 The Author(s). Published by Informa
UK Limited, trading as Taylor & Francis
Group.
Published online: 03 Nov 2023.
Submit your article to this journal
Article views: 173
View related articles
View Crossmark data
Predicting language outcomes in bilingual children with
Down syndrome
Rebecca Ward
a
and Eirini Sanoudaki
b
a
School of Psychology, Swansea University, Swansea, UK;
b
School of Arts, Culture and Language, Bangor
University, Bangor, UK
ABSTRACT
Continuous approaches to measuring bilingualism have recently
emerged as a means of understanding individual variation in lan-
guage abilities. To date, limited information is available to assist in
understanding the language abilities of bilingual children with
Down syndrome (DS), who are specically known to have a large
variation in linguistic outcomes. Group studies in this population
report that children exposed to two languages do not dier from
their monolingual counterparts after considering age and non-
verbal cognitive abilities, although no study to date has examined
the relationship between the amount of exposure to one language
and the linguistic abilities in the other language within this popula-
tion. This study sought to identify whether exposure to an addi-
tional language, specically Welsh, predicted linguistic abilities in
the majority language, in this case, English. Sixty-ve children
between the ages of 5;5–16;9 who had varied linguistic experiences
completed a range of cognitive and linguistic assessments. Results
from hierarchical regression analyses show that the amount of
exposure to Welsh had no impact on language abilities in English,
after controlling for non-verbal cognitive abilities, short-term mem-
ory and socioeconomic status. This demonstrates that exposure to
an additional language does not have a negative impact on lan-
guage development, a nding that has important clinical and edu-
cational implications.
ARTICLE HISTORY
Received 26 May 2023
Accepted 19 October 2023
KEYWORDS
Down syndrome; bilingual;
language acquisition;
developmental disability;
language disorders
The impact of exposure to more than one language on linguistic outcomes is highly
variable due to the heterogeneous nature of bilingual experiences. These experiences not
only vary from individual to individual but are also dynamic and changeable during an
individual’s lifespan. Conceptualizing bilingual experiences has consequently posed
a substantial challenge to researchers, although current measures often consider the
degree of exposure to each language as being a key factor in language outcomes
(Gathercole & Thomas, 2009; Hammer et al., 2012; Thordardottir, 2019), particularly
when considering children in dual-language learning environments. Although several
well-designed and validated tools exist that aim to determine what contributes to an
CONTACT Rebecca Ward r.k.ward@swansea.ac.uk School of Psychology, Swansea University, Bangor SA2 8PP,
UK
CHILD NEUROPSYCHOLOGY
https://doi.org/10.1080/09297049.2023.2275331
© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/
licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or
with their consent.
individual’s bilingual status (such as the Quantifying Bilingual Experiences
Questionnaire and the Language Experience and Proficiency Questionnaire; De Cat
et al., 2022; Marian et al., 2007), methodological challenges exist due to the indirect
measures that are needed to quantify or determine bilingual experiences. As Kremin and
Byers-Heinlein (2021) note, the requirement of multiple measures which include
a number of factors, in itself, suggests that researchers are evidently aware of the multi-
dimensional nature of bilingualism. Furthermore, comparing and contrasting the find-
ings of studies in the field can be onerous due to the diversity of samples and the varying
approaches in defining what constitutes as bilingual.
As a result of viewing bilingualism as a complex interplay of various factors, recent
research has redefined and reconceptualized the notion of this concept. Previously,
a bilingual speaker was defined as an individual with complete native-like control of
both of their languages, or being perfectly balanced in each language (Lambert et al.,
1959). Although this view has been challenged and refined in more recent studies,
traditionally researchers have employed categorical research designs which aim to com-
pare groups, most often bilinguals and monolinguals, on specific aspects of linguistic or
cognitive development. With quantity of language exposure being considered as a key
factor in accounting for variation in performance, alongside various other factors such as
the age and order of acquisition and the quality of parent-child interactions (Bylund
et al., 2019; Siller & Sigman, 2002), more recent approaches to researching bilingualism
have instead proposed that viewing bilingualism on a continuum as a continuous variable
may be more appropriate (Kremin & Byers-Heinlein, 2021; Marian & Hayakawa, 2021).
In doing so, researchers can evaluate the impact that numerous factors have on language
outcomes, which may also help to explain individual variation in linguistic outcomes and
identify subtle differences between individuals or populations.
One population in which this approach might be particularly beneficial is when
researching children with a higher degree of variability in language outcomes, such as
autistic children (Kjelgaard & Tager-Flusberg, 2001) or even more notably children with
Down syndrome (DS), with individual differences being described as a “hallmark of
Down syndrome” (Feltmate & Kay-Raining Bird, 2008, p. 16). DS is the most common
chromosomal disability which is reported to occur in around one in every 700–1000 live
births (Morris & Alberman, 2009; Parker et al., 2010), and frequently results in cognitive
and linguistic challenges, notably difficulties with the development of phonology (Martin
et al., 2009; Roberts et al., 2007) and expressive morphosyntax (Andreou & Katsarou,
2013; Ypsilanti & Grouios, 2008). Relative strengths include semantic, pragmatic (Martin
et al., 2009) and social development with some individuals with DS having a tendency to
have fairly strong skills in engaging with others and orienting attention (Fidler, 2005).
Developmental disabilities and bilingualism
As children with developmental disorders such as DS often have delays and difficulties
with several aspects of language, some have expressed concerns about how these children
would acquire two (or more) languages. The developmental trajectory for children with
DS is not only delayed, but some aspects may be more challenging than others, alongside
the aforementioned and well-documented variability in cognitive and linguistic abilities
(Feltmate & Kay-Raining Bird, 2008; Tsao & Kindelberger, 2009). Although group design
2R. WARD AND E. SANOUDAKI
research studies to date provide concurring evidence that bilingualism does not exacer-
bate these delays and difficulties compared to monolingual control groups (Drysdale
et al., 2015; Kay-Raining Bird et al., 2005, Ward & Sanoudaki, 2021a; Zhou et al., 2019),
clinicians’ advice to parents may not align with the current evidence base. For example,
studies have reported that parents have been advised to limit their language input to
a single language to avoid confusion (Howard et al., 2020; Kay-Raining Bird et al., 2012;
Ware et al., 2015). In some circumstances, parents have even been directed toward the
view that the use of more than one language in the home may even have caused, or
contributed toward their child’s language difficulties with one professional stating that
a child ‘has these problems because he hears so many different languages‘ (Jegatheesan,
2011, p. 195).
Not only are these views unsupported by current evidence, but they may inadvertently
have a negative impact on children’s language outcomes. As Drysdale et al. (2015)
proposed, the use of a non-native language in the home may be less successful if parents
lack fluency in that language and are not as proficient in modeling the language appro-
priately. Moreover, bilingualism is often a natural and necessary feature of some families
and societies. Thus the proposal that parents should abandon or reduce the use of
a native language in the home, may not be practical (Yu, 2016). In contrast, when parents
interact with their children using their native language, research suggests that they are
better able to convey emotions, resulting in increased engagement and potentially more
meaningful interactions (Wharton et al., 2000). This is clearly an area of growing clinical
importance and some recent policies reflect this approach, however, de Valenzuela et al.
(2016) notes that “practice does not always follow policy.”
Researchers investigating the impact of bilingualism on language development in
children with DS specifically report that bilingual children exhibit similar language
profiles as monolingual children with DS when appropriate matching paradigms are
employed (i.e., considering non-verbal IQ and age; Kay-Raining Bird et al., 2005; Ward &
Sanoudaki, 2021b). Earlier case studies also demonstrate that children with DS are
capable of acquiring more than one language, including spoken and signed languages
(Vallar & Papagno, 1993; Woll & Grove, 1996). However, when it comes to children with
developmental disabilities such as DS, quantifying bilingualism might be even more
difficult as standardized assessments are often inappropriate for bilingual children and
it may be difficult to account for bilingual experiences in considering proficiency in each
language. Faced with these challenges, a more appropriate approach to evaluating the
impact of bilingualism on linguistic outcomes may be to consider exposure to an
additional language as a continuous variable. As a result, children’s language abilities
in their additional language can then be examined in relation to the age of first bilingual
exposure (AoE) and degree of exposure (i.e., the frequency and duration of exposure) to
that language.
Accounting for variability in language outcomes
When it comes to understanding the individual differences on children’s language
abilities, Paradis (2023) notes that that are a number of variables internal and external
to the child themselves that are important to consider. For typically developing (TD)
children, studies suggest that relative exposure to each language predicts linguistic
CHILD NEUROPSYCHOLOGY 3
abilities in that language, particularly in the case of minority languages (Gathercole &
Thomas, 2009; Hoff et al., 2012; Thordardottir, 2011). Although some individuals may
have concerns that minority language exposure would negatively affect children’s abil-
ities in the majority language, studies with TD populations report that this is not the case
and that the use of a home language that differs from the majority language has little
impact on language outcomes in the majority language (Cattani et al., 2014; De Cat, 2020;
Papastergiou & Sanoudaki, 2021).
In addition, Thordardottir (2019) investigated how variation in the quantity of
language input and the AoE to each language impacted language outcomes. Findings
from this study demonstrated that differences between simultaneous (children acquiring
two languages from birth) and sequential (children acquiring one language prior to the
introduction of a second) bilinguals were mediated by variations observed in the amount
of exposure that children received in each language. This relationship was not found for
the timing of exposure, suggesting that quantity of exposure, not the age of exposure, has
more of an impact on language outcomes in TD children. However, in a recent review by
Paradis (2023), it was highlighted that the relationship between AoE and language
development is more complex. Here it was suggested that older bilingual children
acquiring a language may be afforded faster initial gains in development. In other
words, children who have a higher AoE often display language gains more quickly
than children with a lower AoE. Additionally, Paradis (2011) noted that child internal
factors overall (such as language aptitude and cognitive maturity) explain more variance
in language outcomes.
Similarly, Bohman et al. (2010) investigated the factors that influence language out-
comes in Spanish-English bilinguals. The authors report that performance in both the L1
(first language) and L2 (second language) were explained by variations in language input
and output, socioeconomic status and age. As a result, this study also suggests that the
amount of exposure to both the L1 and L2 are influential in explaining variation in
language abilities, particularly during the early stages of language acquisition.
Far fewer studies have investigated the impact of bilingual exposure in children with
varying developmental trajectories (Gonzalez-Barrero & Nadig, 2018; Hambly &
Fombonne, 2014), a population in which these apprehensions may be even greater.
One such study that has been conducted in this area specifically explored vocabulary
sizes and morphological abilities in autistic children and found that current language
exposure accounted for a similar degree of variability as it did for TD children (49–62%
of the variance; Gonzalez-Barrero & Nadig, 2018).
For children with DS specifically, a parent-report study suggested that there was
a relationship between vocabulary size and mental age as well as a relationship between
exposure to a second language and language outcomes in that language (Trudeau et al.,
2011). No relationship was found for exposure to a second language (French) and
expressive or receptive language outcomes in the first language (English). Interestingly,
in Kay-Raining Bird et al. (2005) group study of bilingual children with DS, a series of
follow up correlations were conducted which suggested that the duration of exposure to
a second language was not significantly related to first language abilities in children with
DS. The authors caution that the lack of variability seen in the amount and duration of
exposure to a second language in the bilingual children may explain this finding as the
bilingual children may have received “adequate” exposure in their second language, such
4R. WARD AND E. SANOUDAKI
that the amount of exposure was no longer related to performance in the second
language.
Finally, a preliminary study of twelve children (four of whom had DS and were
considered bilingual), involved the examination of individual differences in linguistic
outcomes (Feltmate & Kay-Raining Bird, 2008). The authors reported that measures of
current language input were related to the variability in each of the languages, in this case
English and French (i.e., children with more exposure to French performed higher on the
French language assessments). Due to the very small sample size, no statistical compar-
isons were made, and so caution is needed in interpreting these findings. As a result, very
limited research is available concerning the relationship between exposure to a minority
language with linguistic abilities in the majority language in children with DS. The aim of
the current study will therefore be to expand current understanding of the role of
language input and the AoE on language outcomes in children with DS. This study
will take a novel approach by using continuous measures of language exposure to
investigate any relationship with language outcomes.
Concurrently, utilizing continuous measures in quantifying bilingual experiences is
arguably more suitable for linguistic contexts where two languages are frequently used
alongside each other. The UK is an increasingly multilingual country, but Wales more
specifically has two official languages, meaning that the whole population has some
degree of exposure to an additional language, albeit limited for some individuals.
Welsh is considered a minority language as only around 19% of the population speak
the language fluently according to the latest self-report census (Office for National
Statistics, 2011). English is the majority language and is widely spoken in most commu-
nities. For educational settings, over a quarter of schools in Wales are Welsh-medium
(26.4%) with Welsh being the primary language of instruction. A further 5.4% provide
bilingual instruction, and an additional 2.1% have a dual-stream option meaning that
parents are able to opt for Welsh-medium or English-medium education (Welsh
Government, 2020). Welsh-medium schools are available across the country and chil-
dren from all backgrounds (i.e., homes with English, Welsh or another home language)
are able to access Welsh-medium provisions. As a result, Wales provides a natural
bilingual platform, though the degree of exposure to each language is highly variable
dependent on geographical, cultural and individual factors. Resultingly, this linguistic
setting provides an opportune environment for evaluating the role of language input on
linguistic variability.
Additional predictors of language variation
Several further factors need to be considered when estimating linguistic variability and
will be controlled for in the current study. Firstly, non-verbal cognitive abilities (NVCA)
have been described as being “intertwined” with language outcomes in TD children and
children with “idiopathic intellectual disabilities” (Slušná et al., 2021, p. 2). Furthermore,
NVCA has also been found to predict language gains in young autistic children who had
limited productive vocabulary (Ellis Weismer & Kover, 2015), though similar studies
report a more complex interaction between NVCA and language in autistic children
(Stevens et al., 2000). As children with DS are known to have a lower NVCA compared to
CHILD NEUROPSYCHOLOGY 5
TD children, along with a high degree of variability (Tsao & Kindelberger, 2009),
individual differences in this domain need to be taken into account.
A second predictor which relates to language variability is parental socioeconomic
status (SES). Although conflicting findings have emerged as to how SES might impact
language abilities, it has been suggested that SES impacts both the quality and quantity of
language input that children receive, resulting in reduced language skills (Paradis, 2023).
More specifically, vocabulary development in particular seems to be impacted by lower
parental SES, for both monolingual and bilingual TD children (Biemiller & Slonim, 2001;
Pungello et al., 2009).
This also seems to be the case for children with DS, with studies suggesting that
elevated language abilities are found in children from higher SES backgrounds (Arango
et al., 2018). The final variable that will be controlled for in the present study which is
reported to be associated with language development is phonological short-term memory
(STM). This has been strongly linked to several aspects of linguistic abilities, including
sentence comprehension (Willis & Gathercole, 2001) and phonological awareness, which
in turn also has a mediating effect on word reading skills (Knoop van Campen et al.,
2018). These three key predictors will therefore be controlled for in the present study.
Study aims and research questions
The quantity and breadth of research investigating bilingualism in diverse populations,
including those with developmental disabilities, has increased in recent years, although to
date it is still unclear whether the degree of exposure to an additional or minority
language specially impacts language outcomes in the majority language. In the case of
children with DS, very limited information is available with regards to the variability that
exists in language outcomes and what the role of language input and the AoE has on
language outcomes within a bilingual context. Generally, research consistently reports
that exposure to one language predicts language proficiency in that language (Hurtado
et al., 2014), including for children with neurodevelopmental conditions such as autism
(Gonzalez-Barrero & Nadig, 2018), however, less research has focused on whether the
quantity of exposure to a minority language is directly related to proficiency in the
majority language.
The primary aim of this study is to identify whether there is a relationship between
exposure to a minority language (in this case Welsh) and language proficiency in the
majority language (in this case English). More specifically, we aim to observe whether the
degree of current exposure and the AoE to Welsh predicts English language skills after
controlling for a number of factors identified earlier, that are known to influence
language development. The research questions that will be addressed are:
(1) Does the percentage of current exposure to a minority language (Welsh) predict
language proficiency in the majority language (English) for TD children and
children with DS after controlling for NVCA, STM & SES?
(2) What impact does the AoE to a minority language (Welsh) have on language
proficiency in the majority language (English) for TD children and children with
DS after controlling for NVCA, STM & SES?
6R. WARD AND E. SANOUDAKI
Methods
For this study, both children with a diagnosis of DS and TD children were recruited.
Within these two populations, children were recruited from a variety of linguistic back-
grounds including those with substantial Welsh-language input such as those attending
Welsh-medium schools, alongside children with predominantly English-language expo-
sure attending English-medium schools. As participants were recruited from Wales, the
majority of children received at least a small degree of exposure to Welsh, with Welsh-
medium lessons being a statutory requirement for all public schools in Wales, and with
Welsh being fairly widely used within the public domain (e.g., such as bilingual television
and radio programs). As a result, the aim was to include a sample of children with diverse
language experiences and a varied degree of exposure to both English and Welsh (see
participants section below). Full ethical approval for the study was received from the
University departmental ethical review board.
Participants
A total of 77 children were recruited for the study. The inclusion criteria stipulated that
children with DS should be between five and 16 years of age at the time of data collection,
with the TD children being between three and seven years of age. This meant that the TD
children would be of a similar developmental age to the children with DS. As children
with a dual diagnosis of both DS and ASD often display a differing linguistic and
cognitive profile to children with DS, four bilingual children with both DS and ASD
were excluded from the subsequent analysis but are reported on separately in Ward &
Sanoudaki (2021a). One participant was removed due to being trilingual, with another
removed due to being bilingual in languages other than English and Welsh. A further six
participants were removed as they did not complete all of the assessments, which left
a final sample of 65 children (see Table 1).
The final sample included 25 participants with DS, who were between 5;5–16;9 (mean
= 9;6, SD = 2.98) and there were 40 TD participants who were between 2;11 and 7;10
(mean = 4;3, SD = 1.34). No significant between-group difference was observed between
TD children and children with DS for gender (p = .60) or parental SES (p = .34). Parental
Table 1. Group characteristics of TD participants, participants with DS and the between-group
comparison.
Down
Syndrome
Typically
Developing
Group Comparison
(p value)
Combined
Sample
Age in months *114.60 (35.67) 5.98 (16.13) <.001* 75.45 (4.11)
Gender (% Male) 36.00 42.50 .609 40.00
SES 10.64 (2.12) 11.24 (2.46) .335 1.98 (2.32)
Non-verbal cognitive ability 10.36 (5.68) 11.73 (5.23) .326 11.20 (5.40)
Current Welsh exposure (%) 18.92 (25.41) 28.50 (26.12) .165 24.44 (26.04)
Lifetime Welshexposure (%) 21.28 (28.22) 24.54 (23.42) .628 23.19 (25.34)
Age of exposure (months) 7.64 (15.44) 5.00 (1.23) .552 5.83 (11.94)
Mean scores are reported with standard deviations in parenthesis. Non-verbal cognitive ability represent raw scores on
the non-verbal matrices subtest of the KBIT-II (Kaufman & Kaufman, 2004). Socioeconomic status (SES) was obtained via
parent report in terms of parental education and occupation (scale from 2–14). *Indicates a between-group effect with
p < .05.
CHILD NEUROPSYCHOLOGY 7
SES was calculated as a composite score of parental occupation and education level by
combining Likert scale scores regarding parental occupation and education obtained
from the parental background questionnaire (see below). None of the TD children
displayed any evidence of an intellectual disability, according to their performance on
the cognitive measure (defined as a Z-score within ± 2). Parents of the TD children also
confirmed that their child did not have any known or suspected language impairment or
developmental disorder.
Of the parents/guardians of children with DS, none specified that their child had
mosaic or translocation DS subtypes and children were included if they had no more than
mild hearing loss as determined by parental report. This would subsequently be repre-
sentative of children with DS who frequently have mild or corrected hearing loss. As the
design of the study included TD children at the same developmental age as the children
with DS, the TD children were younger than the children with DS (p < .001). There was
no significant difference between the TD children and the children with DS on their non-
verbal cognitive ability (p = .33). Most of the children with DS were attending main-
stream schools (n = 19, 76%), with a further three (12%) attending a special educational
needs school. One was placed within a specialist unit in a mainstream school (4%), and
two were attending both a special educational needs and a mainstream school on
different days (8%). All TD children were attending mainstream schools or nurseries.
In terms of language exposure, as aforementioned, English is the majority community
language in Wales, meaning that all children received substantial input in English
regardless of home language or the language of schooling. At the same time, the majority
of children received at least a small degree of exposure to Welsh, with Welsh-medium
lessons being a statutory requirement for all public schools in Wales. The amount of
current exposure to Welsh for the TD children varied from 0%-90%. Five children with
DS had a statement of educational need (an official legal document that outlines the
child’s needs and how the education authority will meet these needs within educational
settings), which stipulated that they were exempt from this legal requirement to have
Welsh language lessons, with parental reports indicating that their child received no
exposure to Welsh. Of all participants with DS, current exposure to Welsh ranged from
0% to 90%. Forty-nine percent of participants (10 DS, 22 TD) were attending Welsh-
medium or bilingual schools/nurseries, and 35.4% (8 DS, 15 TD) received Welsh
language input in at least one other setting (e.g., spoken at home by at least one parent).
The AoE to a second language varied from birth to 48 months. The vast majority of
parents who reported that their children had received input in both Welsh and English
stated that they had been exposed to both languages from the outset (71.4%). For the
children with DS, of the parents who reported that their children were exposed to both
languages, 72.7% were exposed from birth. Similarly, 70.8% of typically developing
children received input in both languages from birth.
Materials and procedure
Two organizations who support children with DS and learning difficulties disseminated
information about the research project in order to recruit participants with DS. Typically
developing children were recruited by contacting local Welsh and English-medium
schools and nurseries. Parents or caregivers were provided with an information leaflet,
8R. WARD AND E. SANOUDAKI
consent form and background questionnaire to complete (see below). Once informed
consent was received, children were assessed in either their homes, schools, or
a combination of both, depending on the suitability of these environments. A series of
one-to-one sessions were conducted by the first author on the cognitive and linguistic
measures described below, with the number of sessions varying according to the age and
needs of each child. Assessments were completed in the same pre-defined order. Only the
language of testing was used during each respective session, with the Welsh language
assessments taking place on a different day to the English language assessments. Children
were also administered a Welsh receptive vocabulary assessment and phonological
awareness assessments in English and Welsh, but these are not reported on further
here as they are not relevant for the present study (see Ward & Sanoudaki, 2021b). All
data was stored securely in line with general data protection regulations as both hard
copies and electronically. Participants were assigned a unique ID number so that the data
was anonymous from the point of data collection.
Background questionnaire
Parents or guardians were asked to complete a background questionnaire, which was
provided in their language of choice (Welsh/English or both) and completed either
before or during one-to-one testing sessions with the children. The first section of the
questionnaire aimed to gather essential demographic information about their child (i.e.,
age, hearing status etc.). This included two questions to gather information about
parental socioeconomic status (SES) which included parents’ highest level of education
and occupation. These scales were combined to create a single composite measure of SES.
The next section related to the child’s language background and experiences, which
included parental report of the percentage of time their child was currently exposed to
each language, the percentage of lifetime exposure to each language and the percentage of
time that the child responded in each language. Although direct observations of chil-
dren’s language environment are believed to provide the most accurate representation of
their exposure, parental reports are widely used in the literature and considered to be an
accurate estimate of children’s linguistic exposure (Byers-Heinlein et al., 2020). Further
information regarding home language use, AoE to each language, the consistency of
exposure and any gaps in exposure was obtained, as well as a parent report of their child’s
receptive and expressive language abilities. Measures of current language exposure and
AoE used for the subsequent analyses were calculated based on parent-report estimations
provided in the background questionnaire.
Cognitive measures
In order to assess phonological short-term memory (STM), a forward digit span measure
was used with an increasing length of digits from two upwards. After piloting, a reverse
digit span was deemed too difficult for the children under study, resulting in the decision
to employ a forward digit span measure. Previous research has deemed STM as being
fundamental to language outcomes (Baddeley, 2003), particularly phonological working
memory in the case of children with DS (Baddeley & Jarrold, 2007; Witecy & Penke,
2017). Two trials of each digit length were presented until the participant was no longer
able to recall either sequence within a trial. Prior to the assessment, the children were
asked to count to 10 to ensure that they recognized and could say all the digits and served
CHILD NEUROPSYCHOLOGY 9
as a warm-up to the task. A measure of non-verbal cognitive ability was administered to
ascertain the cognitive development level of each participant. The Kaufman’s Brief
Intelligence Test (KBIT-II; Kaufman & Kaufman, 2004) was utilized for this purpose as
it is a short, standardized assessment with a non-verbal matrices subtest, suitable for the
target populations. Furthermore, the KBIT-II has a high level of internal consistency with
a coefficient of .93 across all ages and a coefficient of .88 for the nonverbal subtest
specifically.
Expressive and receptive language measures
Parent-report instruments can be effective in measuring language production, however,
they may not be as reliable in assessing language comprehension (Feldman et al., 2005;
Tomasello & Mervis, 1994), may be less reliable for those from lower SES (Feldman et al.,
2000) and are also unable to evaluate children’s abilities in everyday contexts (e.g., within
sentences). As a result, a standardized assessment was used to assess expressive, receptive
language abilities in English, the Clinical Evaluation of Language Fundamentals –
Preschool Version (CELF-P, Second Edition; Wiig et al., 2006). This is a clinical diag-
nostic tool that is specifically designed and standardized for children between 3–7 years
old. The core eight subtests were administered: Concepts and Following Directions,
Word Structure, Expressive Vocabulary, Recalling Sentences, Sentence Structure, Basic
Concepts, Recalling Sentences in Context, Word Classes. The CELF-P provides three
main outcome measures: Core, Receptive and Expressive Language, which are calculated
by combining scores on various sub-tests. Core language is calculated by combining
sentence structure, word structure and expressive vocabulary subtests. Receptive lan-
guage is comprised of sentence structure, concepts and following directions, and basic
concepts subtests. The word structure, expressive vocabulary and recalling sentences
subtests are combined to calculate expressive language. Note that there is some overlap in
the subtests which comprise of each language area. As a result, receptive and expressive
language components are the focus of the subsequent analyses. Performance did not
indicate a ceiling effect for expressive or receptive language skills. The internal consis-
tency across all ages is within acceptable standards of between .79 and .97. Internal
consistency is also high for children from clinical groups such as autistic children,
children with hearing disorders and language disorders (alpha coefficients between .87
and .97). As children with DS have developmental ages that do not correspond to their
chronological age, instead the children with DS in the study had developmental ages
within the range specified for the CELF-P (3–7). Raw scores were converted to z-scores
which were used in the subsequent analyses due to the lack of standardized scores
available for children outside of this age range.
Data analysis
As mentioned above, standardized scores from the measures used were not appropriate,
as the participants were outside of the age range for the assessments. Instead, raw scores
were converted to Z scores for all of the English language measures. This also enabled
comparisons between participants with DS and TD participants, as well as comparison
between the different components of language being assessed here: receptive, expressive
language.
10 R. WARD AND E. SANOUDAKI
A two-step hierarchical linear regression was conducted using the enter method to
identify whether exposure to Welsh predicted English language abilities, whilst consider-
ing the influence of the covariates specified earlier which have been identified as
influencing language abilities: NVCA, STM and SES. These are expected to have an
impact on language abilities but are not the focus of this research, and so were included in
the first step of the model. Exposure to Welsh was entered in the second step. Statistical
analyses were conducted using JASP and SPSS.
Results
For a summary of the descriptive statistics for both TD and DS groups on the linguistic
and cognitive measures described above, see Table 2.
In order to satisfy multicollinearity assumptions, the percentage of current and life-
time exposure could not both be entered into the regression model as these were highly
correlated (r = 0.86, p < .001). Preliminary analyses suggested that both the percentage of
current and lifetime exposure to Welsh explained a similar degree of variability in English
language outcomes. As current language exposure to Welsh (r = 0.32) was slightly more
predictive of language abilities compared to lifetime exposure (r = 0.28), current language
exposure to Welsh was used in subsequent analyses. This aligns with previous research
which has also shown that current exposure is more predictive of language outcomes
than lifetime exposure (Cohen, 2016; Hambly & Fombonne, 2014). There were no
outliers, residuals were normally distributed, and inspection of the residuals indicated
that the residuals were homoscedastic.
Does the percentage of current exposure to a minority language (Welsh) predict
language proficiency in the majority language (English) for TD children and children
with DS after controlling for NVCA, STM & SES?
To answer to our first research question, we investigated whether current exposure to
Welsh predicted the variance in English receptive language abilities for TD participants
after controlling for NVCA, STM and SES (see Figure 1). Results from the first step of this
model which included the control variables was significant F(3, 27) = 16.563, p < .001, R
2
= 0.65, R
2
Adjusted = 0.61, ƒ2 = 1.56. This suggested that NVCA, STM and SES explained
a significant amount of variation (61%) in participants’ English receptive language. The
Table 2. Descriptive statistics for linguistic and cognitive measures for
both TD participants and the participants with DS.
Down Syndrome Typically Developing
Core Language 35.88 (17.74) 46.6 (17.62)
Receptive Language* 30.68 (12.34) 39.71 (13.86)
Expressive Language** 32.48 (19.95) 51.22 (22.15)
Short-Term Memory 2.88 (0.83) 3.25 (.71)
Mean raw scores for each of the measures are presented with SD in parenthesis.
Measures for Core, Receptive and Expressive language were obtained using the
Clinical Evaluation of Language Fundamentals – Preschool Edition II (Wiig et al.,
2006). Measures of non-verbal cognitive ability are represented by raw scores on the
non-verbal matrices subtest of the KBIT-II (Kaufman & Kaufman, 2004). Short-term
memory is reported as digit span. *Missing data for two children. ** Missing data for
four children.
CHILD NEUROPSYCHOLOGY 11
addition of the predictor variable (Welsh current exposure) from block 2 did not
significantly improve the model F change (1, 26) = 0.237, p = .630, R
2
Change = 0.003,
R
2
Adjusted = 0.60, ƒ2 = 1.50, which suggests that the amount of exposure to Welsh did
not have an impact on receptive skills in English and did not improve the prediction. The
results from this model are presented in Table 3, which indicate that NVCA had the
largest influence on English receptive language abilities, followed by STM.
The same finding was observed for the children with DS, where the first step of the
model accounted for a significant amount of variation in English receptive language
abilities F(3, 21) = 32.697, p < .001, R
2
= 0.82 R
2
Adjusted = 0.79, ƒ2 = 3.76. The addition
of current Welsh exposure in step 2 again did not improve the prediction change (1, 20)
= 0.147, p = .706, R
2
Change = 0.001, R
2
Adjusted = 0.79, ƒ2 = 3.76. This suggests that
there was no relationship between current exposure to Welsh and receptive language
abilities in English for children with DS or TD participants. For the participants with DS,
Figure 1. Relationship between current exposure to Welsh and receptive language abilities in English
as measured by the CELF-P for children with DS (Down syndrome) and TD (typical development).
Table 3. Regression results for the impact of percentage of current exposure on English receptive
language abilities.
DS Group TD Group
Variable Standardized β t p Standardized β t p
NVCA 0.364 3.100 .006 0.716 5.071 <.001
SES 0.036 0.359 .723 0.043 0.371 .713
STM 0.634 5.217 <.001 0.147 1.043 .306
Current Welsh exposure −0.037 −0.383 .706 −0.057 −0.487 .630
12 R. WARD AND E. SANOUDAKI
STM was the strongest predictor of English receptive language abilities, whereas for the
TD participants NVCA was the strongest predictor.
A second regression model was run to answer the first research question, this time to
identify whether current exposure to Welsh predicted the variance in English expressive
language abilities (see Figure 2). For the TD group, the first step of this model was
significant F(3, 25) = 39.160, p < .001, R
2
= 0.83, R
2
Adjusted = 0.80, ƒ2 = 4.00, suggesting
that NVCA, STM and SES, accounted for a significant amount of variation in partici-
pants’ English expressive language abilities. In block 2, the addition of the predictor
variables (Welsh current exposure) did not significantly improve the model, F change (1,
24) = 2.453, p = .130, R
2
Change = 0.016, R
2
Adjusted = 0.814, ƒ2 = 4.26. The results for
this regression model are presented in Table 4. These findings show that NVCA had the
largest influence on English expressive language abilities.
To explore whether this relationship between English expressive language abilities and
current Welsh language exposure was the same for children with DS, a further regression
model was conducted. The first step of this model was significant F(3, 21 = 6.912, p = .002,
R
2
= 0.50, R
2
Adjusted = 0.43, ƒ2 = 0.75. The addition of Welsh current exposure as
a predictor in step 2 did not improve the prediction, again suggesting that there was no
relationship between current exposure to Welsh and English expressive language abilities
Figure 2. Relationship between current exposure to Welsh and expressive language abilities in English
as measured by the CELF-P for children with DS (Down syndrome) and TD (typical development).
Table 4. Regression results for the impact of percentage of current exposure on English expressive
language abilities.
DS Group TD Group
Variable Standardized β t p Standardized β t p
NVCA 0.288 1.454 .161 0.744 7.185 <.001
SES 0.145 0.868 .368 0.090 1.061 .299
STM 0.446 2.175 .042 0.254 2.465 .021
Current Welsh exposure −0.067 −0.417 .681 −0.128 −1.566 .130
CHILD NEUROPSYCHOLOGY 13
(F change (1, 20) = 0.174, p = .681, R
2
Change = 0.004, R
2
Adjusted = 0.401, ƒ2 = 0.67). For
the participants with DS, STM was the strongest predictor of English expressive language
(see Tables 3 and 4).
Does the AoE to a minority language (Welsh) predict expressive and receptive language
proficiency in the majority language (English) for TD children and children with DS after
controlling for NVCA, STM & SES?
To investigate whether the AoE to Welsh specifically impacted children’s linguistic
abilities in English, a regression model was undertaken to explore this in relation to
receptive language abilities in English specifically, again after controlling for NVCA,
STM and SES. The aim of this analysis was to identify whether the relationship between
AoE to Welsh and English receptive language abilities mirrored that of TD children and
children with DS, and as a result, this regression model was split by DS status. For the TD
group, the first block of this model with the control variables was significant F(3, 19) =
12.257, p < .001, R
2
= 0.66, R
2
Adjusted = 0.61, ƒ2 = 1.56. Within this model, only NVCA
significantly contributed to this mode, suggesting that only NVCA explained the varia-
tion in English receptive language abilities. Block two which included the AoE to Welsh
did not significantly improve this model F change (1, 18) = 0.006, p = .941, R
2
Change =
0.00, R
2
Adjusted = 0.58, ƒ2 = 1.38, suggesting that AoE to Welsh was not related to
English receptive language skills (see Table 5).
Similar findings were found for expressive language abilities for the TD group where the
first block with the control variables was significant F(3, 17) = 31.98, p < .001, R
2
= 0.92, R
2
Adjusted = 0.82, ƒ2 = 4.56. The addition of the AoE to Welsh as an additional variable in
block two did not significantly improve this model F change (1, 16) = 0.350, p = .562, R
2
Change = 0.003, R
2
Adjusted = 0.82, ƒ2 = 4.56 (see Table 6). This showed that AoE to Welsh
was not related to English receptive language skills for TD participants.
A further analysis was conducted to see if this relationship was the same for the DS
group. For receptive language, the first block of this model with the control variables was
significant F(3, 7) = 28.533, p < .001, R
2
= 0.92, R
2
Adjusted = 0.89, ƒ2 = 8.09. Adding AoE
Table 5. Regression results for the impact of age of exposure on English receptive language abilities.
DS Group TD Group
Variable Standardized β t p Standardized β t p
NVCA 0.668 3.512 .013 0.559 3.015 .007
SES 0.175 0.890 .408 −0.019 −0.136 .893
STM 0.350 1.738 .133 0.325 1.784 .091
Welsh age of exposure 0.221 1.250 .258 0.011 0.075 .941
Table 6. Regression results for the impact of age of exposure on English expressive language abilities.
DS Group TD Group
Variable Standardized β t p Standardized β t p
NVCA 0.486 1.095 .315 0.686 5.291 <.001
SES 0.028 0.061 .954 0.149 1.552. .140
STM 0.282 0.599 .571 0.280 2.197 .043
Welsh age of exposure 0.365 0.886 .410 0.058 0.592 .562
14 R. WARD AND E. SANOUDAKI
to Welsh into the model did not improve the prediction, F change (1, 6) = 1.562, p = .258,
R
2
Change = 0.016, R
2
Adjusted = 0.90, ƒ2 = 9.00. This showed that AoE to Welsh was not
related to English receptive language skills for those with DS. Finally, an analysis was
conducted in relation to AoE to Welsh and expressive language abilities. The first block
of this model with the control variables was not significant (though note the p value
indicated that this was approaching significance) F(3, 7) = 3.977, p = .06, R
2
= 0.63, R
2
Adjusted = 0.47, ƒ2 = 0.89. The AoE to Welsh did not improve the model for those with
DS, F change (1, 6) = 0.785, p = .410, R
2
Change = 0.043, R
2
Adjusted = 0.46, ƒ2 = 0.85.
This showed that AoE to Welsh was not related to English receptive language skills for
participants with DS either.
Discussion
The focus of this study was to explore the extent to which variation among children in
their exposure to a minority language predicts language abilities in the majority language,
after controlling for several variables which have been associated with linguistic abilities.
More specifically, the study aimed to identify if there was a relationship between the
degree of current exposure and AoE to Welsh on the one hand and receptive and
expressive language abilities in English on the other hand for both TD children and
children with DS. In answering the first research question, the results demonstrate that
the current amount of exposure to Welsh did not have an impact on receptive or
expressive language abilities in English, after controlling for STM, SES and NVCA. No
significant relationship was observed between the degree of current exposure to Welsh
and performance on the combined sub-components of the CELF-P.
These findings coincide with prior literature that reports that the use of a home
language which differs from the majority language does not have a negative impact on
language outcomes (Cattani et al., 2014; De Cat, 2020; López & Tashakkori, 2004). For
many of the children in the present study, using Welsh at home did not appear to impact
development of the majority language (English). Although the linguistic situation in
Wales is fairly unique with the availability of immersive Welsh-medium education,
findings from previous studies with children who have English as an additional language
seem to also be transferable to this context. For example, studies report that children
attending bilingual educational programs do not have any additional difficulties in
developing English language skills or English literacy skills, when this language is the
majority language (López & Tashakkori, 2004). This view is also supported by the
conclusion proposed by Poarch and Bialystok (2017, p. 187) that “not only is there
ample evidence for the cognitive benefits of bilingualism, but also is there no indication
that the acquisition of the majority language is jeopardized through maintaining a home
language.”
In comparing the TD participants and the participants with DS, findings demonstrate
that there was no evidence to suggest that increased exposure to Welsh had any impact
on English language abilities for TD children, and more importantly, increased exposure
to Welsh had no impact on English language abilities for children with DS in this study
either. These findings substantiate earlier parent-report findings by Trudeau et al. (2011)
as well as an earlier study by Kay-Raining Bird et al. (2005) who reported that the rate or
CHILD NEUROPSYCHOLOGY 15
duration of exposure to a second language did not negatively impact vocabulary sizes in
the first language.
These findings also support the results of studies which report that the amount of
current language exposure account for a similar degree of variability in language out-
comes for autistic children as it does in TD children (Gonzalez-Barrero & Nadig, 2018).
These findings also substantiate the preliminary findings reported by Hambly and
Fombonne (2014), who suggested that current input in each language was related to
the variability in each language in four bilingual children with DS, although their study
did not report the relationship between the impact of exposure of one language on
language outcomes in the alternative language.
Our final research question aimed to identify whether the AoE to Welsh had any
impact on the participants’ linguistic abilities in English. Results suggest that the AoE to
Welsh had no bearing for participants’ English receptive or expressive language abilities.
These findings were found for the TD participants, as well as the participants with DS. To
date, no other study has examined the impact of AoE to an additional language in
bilingual children with DS. These findings coincide with recent findings for TD children
reported by Thordardottir (2019) who also reported that performance on language
measures was not related to the AoE to a second language, although Thordardottir did
report that the amount of input was more strongly related to language abilities. Similarly,
Bedore et al. (2012) also reported that current language exposure was more closely
associated with variation in language outcomes compared to AoE in Spanish-English
bilinguals.
These findings have important implications as they suggest that the use of an addi-
tional language or the AoE to an additional language, specifically a language that differs
to the majority community language, does not negatively impact language outcomes.
Using a continuous measure, these findings suggest that the amount of exposure to an
additional language has no bearing on key abilities in the majority language. These results
extend previous group-design studies which report that children with DS who are
categorized as being bilingual do not have any additional difficulties compared to
monolinguals with DS (Kay-Raining Bird et al., 2005; Ward & Sanoudaki, 2021b).
There are several clinical applications of these findings, for example in relation to advice
provided to parents or caregivers regarding bilingualism. In line with previous studies,
the findings of the present research suggest that parents of children with developmental
disabilities from bilingual backgrounds, or those who desire that their child be raised
bilingually should not be discouraged from doing so. As this study did not find that the
degree or AoE to Welsh was related to language abilities in English for children with DS,
parents or caregivers should not be encouraged to discontinue or even reduce input to an
additional language. An intervention study with this population has found that children
receiving a narrative intervention in both of their languages leads to gains in both
languages as well as cross-language transfer effects (Gorman et al., 2021). This suggests
that speech and language therapy delivery would also benefit from implementing an
approach which includes both languages.
In the present study, three control variables were used to help account for the variation
in language outcomes in English, which were NVCA, SES and STM. Including these
factors as control variables resulted in being able to account for a large degree variability
in English language abilities for both children with DS and TD children (accounting for
16 R. WARD AND E. SANOUDAKI
up to 67% of the variance). Therefore, these variables appear to be important in influen-
cing language development in these populations, although SES did not contribute to any
these models. This suggests that the role of SES in these circumstances is limited, or at
least when compared to the influence of NVCA and STM. Interestingly, for the partici-
pants with DS, STM was the strongest predictor of English expressive and receptive
language abilities, whereas for TD participants NVCA was the strongest predictor in each
model. Although NVCA did significantly predict language outcomes in English for the
participants with DS (with the exception of expressive language), this suggests that the
role of STM is more influential for children with DS. This finding is also supported by
previous studies that have investigated language outcomes in monolinguals (Abbeduto
et al., 2003) and bilinguals with DS (Kay-Raining Bird et al., 2005). This suggests that the
mechanisms underpinning language development may differ for children with DS
compared to TD children, and a focus on developing STM abilities in children with DS
may be successful in enhancing linguistic abilities also.
Strengths and limitations
There are several strengths of this research to highlight. Firstly, the participant recruit-
ment employed a very stringent approach to ensuring that participants had a wide range
of linguistic experiences. This meant that, although there is a relatively small sample size,
the sample was fairly representative of the diverse populations that exist in Wales, and
within bilingual settings more generally. In addition, the approach to data collection was
comprehensive and several measures were used to collect data on cognitive and linguistic
abilities. Although this resulted in a small number of participants being excluded as they
did not complete enough assessments, this provided a thorough understanding of the
participants language abilities and non-verbal cognitive ability, enhancing the validity of
the findings.
There are however several limitations that are also important to note. With regards to
the population size, as noted above there was a fairly small sample size in the current
study, and this is particularly true when conducting analyses on the different populations
here (children with DS and TD children). Although this sample was fairly limited in size,
this is one of the largest studies of bilingual children with DS to date and challenges exist
in recruiting very specialist populations. Nevertheless, further studies with larger sample
sizes in future are needed to substantiate these findings. In considering the sample of the
present study, participants were exposed to English and Welsh specifically. Therefore,
caution is warranted in applying these findings to different contexts, especially contexts
where the additional language may not receive as much support as Welsh and English do
in Wales (i.e., official language status, Welsh-medium immersion nurseries, governmen-
tal policies, and legislation). Future research should endeavor to conduct research in
diverse linguistic contexts to identify whether these findings are transferable to different
circumstances.
Finally, one further limitation to consider is that conceptualizing bilingualism and
attempting to ascertain the degree of exposure that children have to each language is
a challenging task. Due to the ages and developmental abilities of the children in the
current study, it was necessary to obtain this information via the parental-report ques-
tionnaire. As a result, the accuracy of this information may be limited as some parents
CHILD NEUROPSYCHOLOGY 17
may underestimate exposure to a language, whereas others may overestimate this factor.
To further strengthen these findings, a composite score consisting of a number of
bilingual experiences (e.g., from both parents and teachers) may be more appropriate
when using continuous approaches to bilingualism in future studies. Nevertheless,
studies utilizing parent-report methods are widely used and accepted (Byers-Heinlein
et al., 2020).
Conclusion
Challenges arise in conceptualizing bilingual experiences, with more recent approaches
opting for continuous measures of bilingualism such as the degree of exposure to each
language. This approach may help our understanding of individual variability in linguis-
tic outcomes and may be particularly useful in heterogeneous populations, such as
children with DS who display a large degree of variability in language and cognitive
profiles. This study is the first to date to use continuous measures of bilingual experience
to ascertain whether the amount and AoE to a minority language (Welsh) impacted
majority language (English) proficiency in children with DS. In summary, findings
demonstrate that the amount of current exposure and the age of first exposure to
Welsh did not have an impact on receptive or expressive language abilities in English,
after controlling for NVCA, STM and SES. Importantly, this relationship was found not
only for TD children, but children with DS also. The implications arising from these
findings mean that exposure to an additional language (no matter how large or small),
does not seem to impact the development of a majority language. In practice, this means
that clinicians should adopt an evidence-based approach when advising parents and
making decisions around language use in the home, community and clinic, and that
educational provisions should be inclusive when it comes to bilingual opportunities.
Acknowledgments
The authors are very grateful to the funders of this research, the ESRC Wales-DTP studentship
(grant number 1790820) secured by the second author in collaboration with the UK Down’s
Syndrome Association and awarded to the first author. We are very thankful to all the children,
schools and families that participated in this project. We are very grateful to the UK Down’s
Syndrome Association for collaborating and promoting this research with their networks.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
The work was supported by the Economic and Social Research Council [1790820].
ORCID
Rebecca Ward http://orcid.org/0000-0001-7177-3615
18 R. WARD AND E. SANOUDAKI
Eirini Sanoudaki http://orcid.org/0000-0003-1611-8882
Data availability statement
The study materials which include information about the study, the consent form, and the
questionnaires are provided in the supplementary materials and are available on the OSF
(https://osf.io/kywgf/). The analysis code is also available on the OSF (https://osf.io/aj93m). As
the data relates to a very specialist population, the data relating to this study is not publicly
available to ensure participants’ anonymity and privacy.
References
Abbeduto, L., Murphy, M. M., Cawthon, S. W., Richmond, E. K., Weissman, M. D., Karadottir, S.,
& O’Brien, A. (2003). Receptive language skills of adolescents and young adults with down or
fragile X syndrome. American Journal on Mental Retardation. https://doi.org/10.1352/0895-
8017(2003)108<0149:RLSOAA>2.0.CO;2
Andreou, G., & Katsarou, D. (2013). Language learning in children with Down syndrome (DS):
Receptive and expressive morphosyntactic abilities. Procedia - Social & Behavioral Sciences, 93,
921–924. https://doi.org/10.1016/j.sbspro.2013.09.304
Arango, P. S., Aparicio, A., & Tenorio, M. (2018). Developmental trajectories of children with
Down syndrome by socio-economic status: The case of Latin America. Journal of Intellectual
Disability Research, 62(9), 759–774. https://doi.org/10.1111/jir.12516
Baddeley, A. (2003). Working memory and language: An overview. Journal of Communication
Disorders, 36(3), 189–208. https://doi.org/10.1016/S0021-9924(03)00019-4
Baddeley, A., & Jarrold, C. (2007). Working memory and Down syndrome. Journal of Intellectual
Disability Research, 51(12), 925–931. https://doi.org/10.1111/j.1365-2788.2007.00979.x
Bedore, L. M., Peña, E. D., Summers, C. L., Boerger, K. M., Resendiz, M. D., Greene, K.,
Bohman, T. M., & Gillam, R. B. (2012). The measure matters: Language dominance profiles
across measures in Spanish–English bilingual children. Bilingualism, 15(3), 616–629. https://
doi.org/10.1017/S1366728912000090
Biemiller, A., & Slonim, N. (2001). Estimating root word vocabulary growth in normative and
advantaged populations: Evidence for a common sequence of vocabulary acquisition. Journal of
Educational Psychology, 93(3), 498–520. https://doi.org/10.1037/0022-0663.93.3.498
Bohman, T. M., Bedore, L. M., Peña, E. D., Mendez-Perez, A., & Gillam, R. B. (2010). What you
hear and what you say: Language performance in Spanish–English bilinguals. International
Journal of Bilingual Education and Bilingualism, 13(3), 325–344. https://doi.org/10.1080/
13670050903342019
Byers-Heinlein, K., Schott, E., Gonzalez-Barrero, A. M., Brouillard, M., Dubé, D., Jardak, A.,
Laoun-Rubenstein, A., Mastroberardino, M., Morin-Lessard, E., Pour Iliaei, S., Salama-
Siroishka, N., & Tamayo, M. P. (2020). MAPLE: A multilingual approach to parent language
estimates. Bilingualism: Language and Cognition, 23(5), 951–957. https://doi.org/10.1017/
S1366728919000282
Bylund, E., Abrahamsson, N., Hyltenstam, K., & Norrman, G. (2019). Revisiting the bilingual
lexical deficit: The impact of age of acquisition. Cognition, 182, 45–49. https://doi.org/10.1016/j.
cognition.2018.08.020
Cattani, A., Abbot-Smith, K., Farag, R., Krott, A., Arreckx, F., Dennis, I., & Floccia, C. (2014). How
much exposure to English is necessary for a bilingual toddler to perform like a monolingual peer
in language tests? International Journal of Language and Communication Disorders, 49(6),
649–671. https://doi.org/10.1111/1460-6984.12082
Cohen, C. (2016). Relating input factors and dual language proficiency in French–English bilin-
gual children. International Journal of Bilingual Education and Bilingualism, 19(3), 296–313.
https://doi.org/10.1080/13670050.2014.982506
CHILD NEUROPSYCHOLOGY 19
De Cat, C. (2020). Predicting language proficiency in bilingual children. Studies in Second
Language Acquisition, 42(2), 279–325. https://doi.org/10.1017/S0272263119000597
De Cat, C., Kašćelan, D., Prévost, P., Serratrice, L., Tuller, L., & Unsworth, S. (2022). Quantifying
bilingual experience (Q-BEx): Questionnaire manual and documentation. https://doi.org/10.
17605/OSF.IO/V7EC8
de Valenzuela, J. S., Kay-Raining Bird, E., Parkington, K., Mirenda, P., Cain, K., MacLeod, A. A. N.,
& Segers, E. (2016). Access to opportunities for bilingualism for individuals with developmental
disabilities: Key informant interviews. Journal of Communication Disorders, 63, 32–46. https://
doi.org/10.1016/j.jcomdis.2016.05.005
Drysdale, H., van der Meer, L., & Kagohara, D. (2015). Children with autism spectrum disorder
from bilingual families: A systematic review. Review Journal of Autism and Developmental
Disorders, 2(1), 26–38. https://doi.org/10.1007/s40489-014-0032-7
Ellis Weismer, S., & Kover, S. T. (2015). Preschool language variation, growth, and predictors in
children on the autism spectrum. Journal of Child Psychology and Psychiatry and Allied
Disciplines, 56(12), 1327–1337. https://doi.org/10.1111/jcpp.12406
Feldman, H. M., Dale, P. S., Campbell, T. F., Colborn, D. K., KursLasky, M., Rockette, H. E., &
Paradise, J. L. (2005). Concurrent and predictive validity of parent reports of child language at
ages 2 and 3 years. Child Development, 76(4), 856–868.
Feldman, H. M., Dollaghan, C. A., Campbell, T. F., Kurs-Lasky, M., Janosky, J. E., & Paradise, J. L.
(2000). Measurement properties of the MacArthur communicative development inventories at
ages one and two years. Child Development, 71(2), 310–322. https://doi.org/10.1111/1467-8624.
00146
Feltmate, K., & Kay-Raining Bird, E. (2008). Language learning in four bilingual children with
Down syndrome: A detailed analysis of vocabulary and morphosyntax/L’apprentissage du
langage chez quatre enfants bilingues atteints du syndrome de Down: Une analyse detaillee
du vocabulaire et de la morph. Canadian Journal of Speech-Language Pathology & Audiology, 32
(1), 6.
Fidler, D. J. (2005). The emerging down syndrome behavioral phenotype in early childhood:
Implications for practice. Infants and Young Children, 18(2), 86–103. https://doi.org/10.1097/
00001163-200504000-00003
Gathercole, V. C. M., & Thomas, E. M. (2009). Bilingual first-language development: Dominant
language takeover, threatened minority language take-up. Bilingualism: Language and
Cognition, 12(2), 213–237. https://doi.org/10.1017/S1366728909004015
Gonzalez-Barrero, A. M., & Nadig, A. (2018). Bilingual children with autism spectrum disorders:
The impact of amount of language exposure on vocabulary and morphological skills at school
age. Autism Research, 11(12), 1667–1678. https://doi.org/10.1002/aur.2023
Gorman, B. K., Martinez, G., & Pina Garcia, L. (2021). Dual-language narrative intervention
outcomes for a bilingual adolescent with down syndrome. Bilingual Research Journal, 44(4),
444–465. https://doi.org/10.1080/15235882.2021.1999340
Hambly, C., & Fombonne, E. (2014). Factors influencing bilingual expressive vocabulary size in
children with autism spectrum disorders. Research in Autism Spectrum Disorders, 8(9),
1079–1089. https://doi.org/10.1016/j.rasd.2014.05.013
Hammer, C. S., Komaroff, E., Rodriguez, B. L., Lopez, L. M., Scarpino, S. E., & Goldstein, B. (2012).
Predicting Spanish–English bilingual children’s language abilities. Journal of Speech, Language,
& Hearing Research, 55(5), 1251–1264. https://doi.org/10.1044/1092-4388(2012/11-0016)
Hoff, E., Core, C., Place, S., Rumiche, R., Señor, M., & Parra, M. (2012). Dual language exposure
and early bilingual development. Journal of Child Language, 39(1), 1–27. https://doi.org/10.
1017/S0305000910000759
Howard, K., Gibson, J., & Katsos, N. (2020). Parental perceptions and decisions regarding
maintaining bilingualism in autism. Journal of Autism and Developmental Disorders, 51(1),
179–192. https://doi.org/10.1007/s10803-020-04528-x
Hurtado, N., Grüter, T., Marchman, V. A., & Fernald, A. (2014). Relative language exposure,
processing efficiency and vocabulary in Spanish–English bilingual toddlers. Bilingualism, 17(1),
189–202. https://doi.org/10.1017/S136672891300014X
20 R. WARD AND E. SANOUDAKI
Jegatheesan, B. (2011). Multilingual development in children with autism: Perspectives of South
Asian Muslim immigrant parents on raising a child with a communicative disorder in multi-
lingual contexts. Bilingual Research Journal, 34(2), 185–200. https://doi.org/10.1080/15235882.
2011.597824
Kaufman, A. S., & Kaufman, N. L. (2004). Kaufman brief intelligence test (2nd ed.). Pearson, Inc.
Kay-Raining Bird, E., Cleave, P., Trudeau, N., Thordardottir, E., Sutton, A., Thorpe, A., Bird, E. K.,
Cleave, P., Trudeau, N., Thordardottir, E., Sutton, A., & Thorpe, A. (2005). The language
abilities of bilingual children with Down syndrome. American Journal of Speech-Language
Pathology, 14(3), 187–199. https://doi.org/10.1044/1058-0360(2005/019)
Kay-Raining Bird, E., Lamond, E., & Holden, J. (2012). Survey of bilingualism in autism spectrum
disorders. International Journal of Language & Communication Disorders/Royal College of
Speech & Language Therapists, 47(1), 52. https://doi.org/10.1111/j.1460-6984.2011.00071.x
Kjelgaard, M. M., & Tager-Flusberg, H. (2001). An investigation of language impairment in
autism: Implications for genetic subgroups. Language and Cognitive Processes, 16(2–3),
287–308. https://doi.org/10.1080/01690960042000058
Knoop van Campen, C. A. N., Segers, E., & Verhoeven, L. (2018). How phonological awareness
mediates the relation between working memory and word reading efficiency in children with
dyslexia. Dyslexia, 24(2), 156–169. https://doi.org/10.1002/dys.1583
Kremin, L. V., & Byers-Heinlein, K. (2021). Why not both? Rethinking categorical and continuous
approaches to bilingualism. International Journal of Bilingualism, 25(6), 1560–1575. https://doi.
org/10.1177/13670069211031986
Lambert, W. E., Havelka, J., & Gardner, R. C. (1959). Linguistic manifestations of bilingualism. The
American Journal of Psychology, 72(1), 77. https://doi.org/10.2307/1420213
López, M. G., & Tashakkori, A. (2004). Effects of a two-way bilingual program on the literacy
development of students in kindergarten and first grade. Bilingual Research Journal, 28(1),
19–34. https://doi.org/10.1080/15235882.2004.10162610
Marian, V., Blumenfeld, H. K., & Kaushanskaya, M. (2007). The language experience and
proficiency questionnaire (LEAP-Q): Assessing language profiles in bilinguals and
multilinguals. Journal of Speech, Language, & Hearing Research, 50(4), 940–967. https://doi.
org/10.1044/1092-4388(2007/067)
Marian, V., & Hayakawa, S. (2021). Measuring bilingualism: The quest for a “bilingualism
quotient”. Applied Psycholinguistics, 42(2), 527–548. https://doi.org/10.1017/
S0142716420000533
Martin, G. E., Klusek, J., Estigarribia, B., & Roberts, J. E. (2009). Language characteristics of
individuals with down syndrome. Topics in Language Disorders, 29(2), 112–132. https://doi.org/
10.1097/TLD.0b013e3181a71fe1
Morris, J. K., & Alberman, E. (2009). Trends in Down’s syndrome live births and antenatal
diagnoses in England and Wales from 1989 to 2008: Analysis of data from the national down
syndrome cytogenetic register. BMJ, 339. https://doi.org/10.1136/bmj.b3794
Office for National Statistics. (2011). Census data. Office for National Statistics, 288154230, 2011.
http://www.ons.gov.uk/ons/guide-method/census/2011/index.html?utm_source=twitterfee
d&utm_medium=twitter
Papastergiou, A., & Sanoudaki, E. (2021). Language skills in Greek-English bilingual children
attending Greek supplementary schools in England. International Journal of Bilingual
Education and Bilingualism, 25(8), 2834–2852. https://doi.org/10.1080/13670050.2021.1980496
Paradis, J. (2011). Individual differences in child English second language acquisition: Comparing
child-internal and child-external factors. Linguistic Approaches to Bilingualism, 1(3), 213–237.
https://doi.org/10.1075/lab.1.3.01par
Paradis, J. (2023). Sources of individual differences in the dual language development of heritage
bilinguals. Journal of Child Language, 50(4), 793–817. https://doi.org/10.1017/
s0305000922000708
Parker, S. E., Mai, C. T., Canfield, M. A., Rickard, R., Wang, Y., Meyer, R. E., Anderson, P.,
Mason, C. A., Collins, J. S., Kirby, R. S., & Correa, A. (2010). Updated National birth prevalence
CHILD NEUROPSYCHOLOGY 21
estimates for selected birth defects in the United States, 2004-2006. Birth Defects Research, 88
(12), 1008–1016. https://doi.org/10.1002/bdra.20735
Poarch, G. J., & Bialystok, E. (2017). Konsequenzen der Mehrsprachigkeit von Migranten für die
sprachliche Bildung. Zeitschrift Für Erziehungswissenschaft, 20(2), 175–191. https://doi.org/10.
1007/s11618-017-0739-1
Pungello, E. P., Iruka, I. U., Dotterer, A. M., Mills-Koonce, R., & Reznick, J. S. (2009). The effects of
socioeconomic status, race, and parenting on language development in early childhood.
Developmental Psychology, 45(2), 544–557. https://doi.org/10.1037/a0013917
Roberts, J. E., Price, J., & Malkin, C. (2007). Language and communication development in down
syndrome. Mental Retardation and Developmental Disabilities Research Reviews, 13(1), 26–35.
https://doi.org/10.1002/mrdd.20136
Siller, M., & Sigman, M. (2002). The behaviors of parents of children with autism predict the
subsequent development of their children’s Communication. Journal of Autism and
Developmental Disorders, 32(2), 77–89. https://doi.org/10.1023/A:1014884404276
Slušná, D., Rodríguez, A., Salvadó, B., Vicente, A., & Hinzen, W. (2021). Relations between
language, non-verbal cognition, and conceptualization in non- or minimally verbal individuals
with ASD across the lifespan. Autism & Developmental Language Impairments, 6,
239694152110532. https://doi.org/10.1177/23969415211053264
Stevens, M. C., Fein, D. A., Dunn, M., Allen, D., Waterhouse, L. H., Feinstein, C., & Rapin, I.
(2000). Subgroups of children with autism by cluster analysis: A longitudinal examination.
Journal of the American Academy of Child and Adolescent Psychiatry, 39(3), 346–352. https://
doi.org/10.1097/00004583-200003000-00017
Thordardottir, E. (2011). The relationship between bilingual exposure and vocabulary
development. International Journal of Bilingualism, 15(4), 426–445. https://doi.org/10.1177/
1367006911403202
Thordardottir, E. (2019). Amount trumps timing in bilingual vocabulary acquisition: Effects of
input in simultaneous and sequential school-age bilinguals. International Journal of
Bilingualism, 136700691772241. https://doi.org/10.1177/1367006917722418
Tomasello, M., & Mervis, C. B. (1994). The instrument is great, but measuring comprehension is
still a problem. Monographs of the Society for Research in Child Development, 59(5), 174–179.
https://doi.org/10.1111/j.1540-5834.1994.tb00186.x
Trudeau, N., Kay-Raining Bird, E., Sutton, A., & Cleave, P. L. (2011). Développement lexical chez
les enfants bilingues avec Trisomie 21. Enfance, 2011(3), 383–404. https://doi.org/10.4074/
S0013754511003089
Tsao, R., & Kindelberger, C. (2009). Variability of cognitive development in children with Down
syndrome: Relevance of good reasons for using the cluster procedure. Research in
Developmental Disabilities, 30(3), 426–432. https://doi.org/10.1016/j.ridd.
Vallar, G., & Papagno, C. (1993). Preserved vocabulary acquisition in Down’s syndrome: The role
of phonological short-term memory. Cortex, 29(3), 467–483. https://doi.org/10.1016/S0010-
9452(13)80254-7
Ward, R., & Sanoudaki, E. (2021a). Bilingualism in Children with a Dual Diagnosis of Down
Syndrome and Autism Spectrum Disorder. Clinical Linguistics & Phonetics, 35(7), 663–689.
https://doi.org/10.1080/02699206.2020.1818288
Ward, R., & Sanoudaki, E. (2021b). Language profiles of Welsh-English bilingual children with
down syndrome. Journal of Communication Disorders, 93, 106126. https://doi.org/10.1016/j.
jcomdis.2021.106126
Ware, J., Lye, C. B., & Kyffin, F. (2015). Bilingualism and students (learners) with Intellectual
disability: A review. Journal of Policy and Practice in Intellectual Disabilities, 12(3), 220–231.
https://doi.org/10.1111/jppi.12124
Welsh Government. (2020). No schools by local authority, region and welsh medium type. https://
statswales.gov.wales/v/H-Ax
Wharton, R. H., Levine, K., Miller, E., Breslau, J., & Greenspan, S. (2000). Children with special
needs in bilingual families: A developmental approach to language recommendations.
22 R. WARD AND E. SANOUDAKI
Wiig, E., Secord, W., & Semel, E. (2006). The clinical evaluation of language
fundamentals-preschool 2. Age & Ageing, 35(5), 503–507. https://doi.org/10.1093/ageing/afl058
Willis, C. S., & Gathercole, S. E. (2001). Phonological short-term memory contributions to
sentence processing in young children. Memory, 9(4–6), 349–363. https://doi.org/10.1080/
09658210143000155
Witecy, B., & Penke, M. (2017). Language comprehension in children, adolescents, and adults with
down syndrome. Research in Developmental Disabilities, 62, 184–196. https://doi.org/10.1016/j.
ridd.2017.01.014
Woll, B., & Grove, N. (1996). On language deficits and modality in children with Down syndrome:
A case study. Proceedings of the Annual Boston University Conference on Language Development,
20(2), 837–848.
Ypsilanti, A., & Grouios, G. (2008). Linguistic profile of individuals with Down syndrome:
Comparing the linguistic performance of three developmental disorders. Child
Neuropsychology, 14(2), 148–170. https://doi.org/10.1080/09297040701632209
Yu, B. (2016). Bilingualism as conceptualized and bilingualism as lived: A critical examination of
the monolingual socialization of a child with autism in a bilingual family. Journal of Autism and
Developmental Disorders, 46(2), 424–435. https://doi.org/10.1007/s10803-015-2625-0
Zhou, V., Munson, J. A., Greenson, J., Hou, Y., Rogers, S., & Estes, A. M. (2019). An exploratory
longitudinal study of social and language outcomes in children with autism in bilingual home
environments. Autism, 23(2), 394–404. https://doi.org/10.1177/1362361317743251
CHILD NEUROPSYCHOLOGY 23
