Literacy & Dyslexia Revealed through Bilingual Brain Development

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April 2016

By Ioulia Kovelman, Silvia Bisconti, and Fumiko Hoeft

Reading is one of the most important skills learned in early childhood. Yet many young learners fail to meet the national standards in reading achievement, and young bilingual learners often are represented in this low-achieving group (Pugh et al., 2011). The goal of this paper is to explore how bilingualism affects the development of literacy in bilinguScience of Dyslexia Iconal children, bilingual children with dyslexia, and monolingual children with dyslexia who are learning to read in a new language.

Impact of Bilingualism on Learning to Read?

Even when using only one of their languages, bilinguals often access linguistic and orthographic representations of their other language (Kroll & Bialystok, 2013). Such tight interaction between bilinguals’ two languages facilitates the bidirectional sharing or “transfer” of literacy knowledge gained in one language towards learning to read in another language (Cummins, 2012).

For example, studies comparing bilinguals learning English and a language with a more phonologically-transparent orthography (e.g., Spanish, Portuguese, or Italian) have shown that these bilinguals outperform English monolinguals on phonological literacy tasks, such as nonword reading (Kovelman et al., 2008; Siegel, in press). Evidence of the benefits of cross-linguistic transfer has also been found for speakers of similar (e.g., Spanish-English) as well as more distal languages (e.g., Arabic-English and Chinese-English). The implication of this evidence is that bilingualism might improve the flexibility of children’s metalinguistic cognition for learning to read  (Siegel, in press).

…bilingualism might improve the flexibility of children’s metalinguistic cognition for learning to read.

Similar to the behavioral evidence, neuroimaging research suggests that childhood bilingual exposure to a more phonologically-transparent language can impact children’s neural circuitry for learning to read in their more phonologically-opaque language (Das et al., 2011; Jasinska et al., under review). For instance, when reading nonwords in English, young Spanish-English and French-English bilinguals showed greater activation in left superior temporal and lower activation in left inferior frontal regions, as compared to English monolinguals. Left temporal regions are thought to support phonological analyses for more direct and rule-governed sound-to-print mappings (Paulesu et al., 2000).

Dysfunction of left posterior temporal regions is often implicated in dyslexia (Hoeft et al., 2007), which raises the tantalizing possibility that early bilingual exposure might have a positive impact on the developmental plasticity of these regions in people with dyslexia.

…early bilingual exposure might have a positive impact on the developmental plasticity of these regions in people with dyslexia.

In sum, accumulating evidence with bilingual learners of two alphabetic languages suggests that learning in a phonologically-transparent orthography (e.g., Spanish) might improve children’s phonological reading skills and increase the strength of left superior temporal activation in their phonologically-opaque language (e.g., English).

Impact of Bilingualism on Dyslexia?

Bilingualism is a fundamentally linguistic experience. The focus of this article will be on the impact of bilingualism on language-related processes in dyslexia, such as phonological awareness.

Learners of Similar Scripts. Studies of bilingual children learning to read in two alphabetic orthographies have shown that children with dyslexia present with similar reading deficits in both of their languages (Klein & Doctor, 2003). These deficits are likely to be phonological and are likely to impede children’s acquisition of print to sound correspondences in both of their languages (Geva et al., 2000).

At the same time, this does not preclude young bilinguals with dyslexia from developing language-specific reading strategies in each of their languages. For example, bilingual children learning to read in English and Afrikaans (a language that has descended from Dutch and is more phonologically-transparent than English) have been found to have phonological deficits in each of their languages.

Nevertheless, when reading Afrikaans, the more phonologically transparent language, these Afrikaans-English bilinguals with dyslexia applied a phonological, sounding-out strategy (Klein & Doctor, 2003)—similar to typically developing readers of Afrikaans. When reading English, the more opaque language, these Afrikaans-English bilinguals with dyslexia applied both phonological, sounding-out strategies (for phonologically predictable words) and additional lexical, meaning-based strategies (for phonologically unpredictable words)—similar to typically developing readers of English.

An important implication of this and similar findings is that bilingual children with dyslexia can and do benefit from early literacy intervention under certain circumstances:

  • Even if this intervention can be made available only in one of the children’s languages
  • If they have not yet achieved full spoken language proficiency in the language of the intervention (Geva et al., 2000).

More intriguingly, however, bilingual children with dyslexia who are learning to read in a phonologically-transparent orthography (Italian) have also been found to have better phonological literacy skills in their phonologically-opaque language (English) than their monolingual English peers with dyslexia (Siegel, in press). It is therefore possible that in the case of bilingual learners of two alphabetic scripts, for both typical learners and those with dyslexia, bilingual exposure has a positive impact on children’s phonological reading skills. 

It is therefore possible that in the case of bilingual learners of two alphabetic scripts, for both typical learners and those with dyslexia, bilingual exposure has a positive impact on children’s phonological reading skills.

Learners of Different Scripts. Similar to alphabetic languages, phonological awareness is also important for learning to read in character-based languages like Chinese (Ho et al., 2005). Chinese-English bilinguals have been found to transfer phonological reading skills across their two languages (Geva et al., 2000). Chinese children with dyslexia are likely to have lower levels of phonological awareness and difficulty learning English as a second language (Ho et al., 2005). In addition, they show reduced activation in temporo-parietal brain regions when completing literacy tasks in English (You et al., 2011).

Yet it appears that among Chinese-English bilingual children with reading deficits, only about 30 to 40% show signs of dyslexia in both of their languages (Kalindi et al., 2015; McBride et al., 2012). In Chinese-English bilinguals with Chinese-only reading impairments, these impairments are often characterized by select deficits in morphological awareness (McBride et al., 2013). Morphological awareness, the ability to manipulate the smallest units of meaning (e.g., football = foot+ball, undo = un+do), is important for learning to read across orthographies, especially in Chinese where characters often map onto morphemic units (McBride et al., 2012).

Newly-emerging evidence suggests both an overlap and a dissociation between the brain bases for phonological and morphological awareness (Arredondo et al., 2015). This overlap might be greater in Chinese than in Indo-European languages (Zhao et al., 2014). The nature of this overlap may help explain why bilingual Chinese-English children who show signs of dyslexia in both languages, compared to only one, exhibit more severe deficits in both phonological and morphological awareness  (McBride et al., 2013). Recent evidence suggests that during morphological awareness tasks in Chinese (as compared to a control word matching-task), adult typical readers of Chinese show significant activation in posterior superior temporal regions typically associated with phonological analyses as well as middle temporal regions typically associated with lexico-semantic analyses (Ip et al., in preparation).

It is therefore possible that phonological deficits in dyslexia in alphabetic languages and morphological deficits in dyslexia in Chinese have a common deficit of manipulating the most salient morpho-phonological units (Frost, 2012) of children’s respective languages. In particular, in English these salient units are likely to be meaningless phonological units such as syllables in the word cat-er-pil-lar, and in Chinese these salient units are likely to be meaningful morphemic units such as in the word foot-ball. This dysfunction in operating upon these phonological and morphological units is likely associated with the functionality of left posterior temporal regions. Research with bilingual children with dyslexia learning typologically contrasting languages (e.g., English and Chinese) will be the key to understanding the language-specific and the universal mechanisms of literacy and dyslexia across languages.

Concluding Notes for Parents, Individuals with Dyslexia, and Practitioners

If my child is bilingual and has dyslexia, what should I do?

Ideally, we should ensure that the child has the opportunity to learn to read sufficiently in his or her primary language of use at the same time as the child learns to read less familiar languages. Learning to read requires linking spoken language representations with print, which is best accomplished in the language of greatest proficiency (Goldenberg, 2008; Mortimore et al., 2012). This will allow the child to form the basics of literacy that she can then transfer from her native language into her new language (Cummins et al., 2012). Bilingual children with dyslexia can and eventually do form language-specific literacy skills in both of their languages (Klein & Doctor, 2003).

If my child is monolingual and has dyslexia, is it OK to learn a second language?

In many parts of the world, whether one has dyslexia or not, children must learn to read in more than one language. Unfortunately, children with dyslexia will find it difficult and time-consuming to learn to read in a new language, regardless of whether the language has a similar or a different orthography (Ho et al., 2005). There is no evidence, however, to suggest that bilingualism somehow “damages” literacy acquisition; instead, it may be beneficial to children with and without dyslexia as we state above in terms of transfer of language skills (Siegel, in press). Further, some bilingual children with dyslexia actually enjoy learning to read in foreign languages (Miller-Guron, & Lundberg, 2000).


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Ioulia Kovelman, Ph.D., is an Assistant Professor at the University of Michigan, Department of Psychology & Center for Human Growth and Development. Her research focuses on bilingual language and reading acquisition in young children. She is especially interested in how bilingual exposure to different types of languages affects both the language ability and the neural architecture for learning to speak and to read. To accomplish these research goals, she studies bilingual infants, children, and adults using both behavioral and neuroimaging methodologies. For more information, please visit the language and literacy laboratory website at

Silvia Bisconti, Ph.D., is a post-doctoral fellow at the Center for Human Growth and Development, University of Michigan. Her research focuses on language and early childhood development. In particular, she is interested in how early life experience and biological factors influence language acquisition. She uses behavioral techniques and functional near-infrared spectroscopy (fNIRS) to investigate the neural circuitry—and its plasticity—for neural specialization for language and other higher cognitive functions.

Fumiko Hoeft, MD, Ph.D., is Associate Professor of Child & Adolescent Psychiatry, Director of Laboratory for Educational Neuroscience (, Board Member of the Dyslexia Center at the University of California, San Francisco (UCSF) and the IDA, and Research Scientist at Haskins Laboratories. She was the 2014 Geschwind Memorial Lecturer of the IDA. LENS is interested in how cognitive science can inform educational and clinical practices, with specific interests in understanding the neurobiological cause of dyslexia, early identification and prediction, and the emotional resilience necessary to succeed.

More of Dr. Fumiko’s Science of Dyslexia:

Summer Vacation: Important Insights for Reading Development, by Joanna A. Christodoulou, Ed.D. and Fumiko Hoeft, M.D., Ph.D. (June 2015 )
The Myths and Truths of Dyslexia in Different Writing Systems, by Fumiko Hoeft, M.D., Ph.D., Peggy McCardle, Ph.D., M.P.H., and Kenneth Pugh, Ph.D. (March 2015)
Many Layers of Dyslexia: Gene Discovery Is Just the Beginning, by Fumiko Hoeft, M.D., Ph.D., and Albert Galaburda, M.D. (December 2014)
Meet Fumiko Hoeft, M.D., Ph.D., Q&A with Geschwind Memorial Lecturer (September 2014)
The Emerging Field of Neuroscience Is Changing the Landscape of Dyslexia Research and Practice, by Fumiko Hoeft, M.D., Ph.D., UCSF and Chelsea Myers, BSC, UCSF (July 2014)
New Scientific Evidence Sheds Light on the Phoneme Debate, by Fumiko Hoeft, M.D., Ph.D. (March 2014)

[*] Please note that you can find a discussion on dyslexia in monolingual children across languages in The Myths and Truths of Dyslexia in Different Writing Systems, by Hoeft, McCardle, Pugh, 2015.

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