Lay Publication Details

The influence of bilingualism on speech production: A systematic review

Easy Access Summary

The influence of bilingualism on speech production: A Systematic Review
There is an increase in the number of children who speak more than one language (bilingual) entering the school system in English-speaking countries. This has implications for speech and language therapists as we know that children who are bilingual, and have a speech sound disorder, are less likely to be referred to speech and language therapy.  It can be difficult for speech and language therapists to know whether a child has a speech sound disorder or whether they are slow to learn English because they speak other languages at home.
The review identified all the previous studies that have investigated the development of language in English speaking bilingual infants and children. The article comments on how exposure to more than one language can impact a child’s ability to speak English. It also investigates research in to how these bilingual children with a speech sound disorder are identified and treated.
Findings from the review reported no clear evidence for ‘typically developing’ bilingual children learning speech at a slower or faster rate than their peers, but it is clear that bilingual children learn speech differently from their peers who speak a single language.  Bilingual children can produce atypical sounds in one or both languages, they show delayed acquisition of some sounds and accelerated acquisition of others, depending on interactions between languages spoken, and there is greater variation in rates of speech acquisition compared to monolingual children.  Even though more research is needed for conclusive evidence into the subject, findings from the review emphasise the importance for speech and language therapists to take a careful case history and assess speech sound production in both languages of a bilingual child.


H. Hambly; Y. Wren; S. McLeod; S. Roulstone


Background: Children who are bilingual and have speech sound disorder are likely to be under-referred, possibly
due to confusion about typical speech acquisition in bilingual children.
Aims: To investigate what is known about the impact of bilingualism on children’s acquisition of speech in English
to facilitate the identification and treatment of bilingual children with speech sound disorder.
Methods & Procedures: A systematic review of studies from the last 50 years was conducted. Studies investigating
speech acquisition in bilingual infants and children (where one language was English) were identified
through searching seven electronic databases, bibliographies of relevant articles and e-mailing authors. Sixtysix
studies investigating bilingual speech production met inclusion criteria, with 53 describing typically
developing children and 13 describing children with speech sound disorder. The 66 studies were analysed
thematically and summarized in terms of methods, key findings and underlying theories.
Main Contribution: There was limited evidence to suggest that bilingual children develop speech at a slower rate
than their monolingual peers; however, there was evidence for qualitative differences and increased variation in
speech production. Nearly all studies provide evidence for transfer between the two phonological and language
structures, although the amount of transfer varied between studies. There was evidence of positive and negative
transfer of features from the dominant language (L1) to the second language (L2) as well as from L2 to L1. Positive
transfer became more evident with increased age and length of exposure to a second language. More recently
researchers have moved away from investigating whether there are one or two phonological systems and accept
that there are two systems that interact. Interest has shifted to examining how phonological systems interact and
to identifying factors that influence interactions. The review revealed a number of inconsistencies in the findings
of studies due to differences in methodology, languages investigated and degree of language exposure. Overall,
measurement issues were addressed well but most studies provided limited sample information about language
experience, schooling and socio-economic status.
Conclusions & Implications: There are differences in speech sound acquisition between monolingual and bilingual
children in terms of rate and patterns of error, with both positive and negative transfer occurring in bilingual