Bilingualism Did Not Deepen the Dyslexia

What the research found

Maria Vender and Chiara Melloni, both at the University of Verona, set out to answer a question that worries a great many families. When a child has dyslexia, does raising that child with two languages make the reading difficulty worse? The fear is common, and it is often repeated by teachers and clinicians. This study tested it directly.

The researchers assessed 148 children, all around ten years old, across two linked studies. Every child was tested on three tasks that measure phonological awareness, which is the ear for the sound structure of words that underpins learning to read. The first task was nonword repetition, in which the child repeats invented words such as made-up nonsense strings. The second was rhyme detection, picking which of several words rhymes with a target. The third, the hardest, was the spoonerism task, swapping the opening sounds of two words so that “dog, fine” becomes “fog, dine”. That last task leans heavily on working memory, and it is where children with dyslexia tend to founder.

The first study, with 40 typically developing children, checked a background assumption. It compared Italian monolinguals with two groups of bilinguals learning Italian as a second language, one group with Romanian as a first language and one with Arabic. Romanian is phonologically close to Italian; Arabic is more distant. The bilingual children scored just like the monolinguals on all three tasks, with no statistically significant differences and no effect of the first language. In plain terms, bilingualism on its own neither helped nor hindered the ear for sound.

The second study is the one that matters for families. It tested 108 children in four groups: 24 monolingual children with dyslexia, 30 monolingual children developing typically, 24 bilingual children with dyslexia, and 30 bilingual children developing typically. The groups were matched on age and on non-verbal intelligence. The pattern was clear and consistent. On every task, the two groups with dyslexia scored significantly below the two groups without it, and the gap was widest on the demanding spoonerism task. There, the typically developing children handled roughly three quarters of the items (monolinguals 0.73, bilinguals 0.75), while the children with dyslexia managed around half (bilinguals 0.50, monolinguals 0.41). The differences on rhyme detection and nonword repetition were smaller but ran the same way.

The crucial comparison is between the two groups of children with dyslexia. Bilingual and monolingual children with dyslexia performed alike on all three phonological tasks, with no statistically significant difference between them. Bilingualism added no extra burden. If anything, one incidental finding tilted the other way: on the timed reading checks, bilingual children with dyslexia were faster than their monolingual counterparts, though both groups read poorly. The authors are careful, and so should we be, in reading too much into that stray advantage.

What it means for you and your child

The headline is reassuring and worth stating plainly. In this sample, being bilingual did not make dyslexia worse. The difficulties that define dyslexia, particularly the struggle to hold and manipulate the sounds of words, showed up strongly in the children who had it. But whether those children spoke one language or two made no measurable difference to how severe those difficulties were. If your family speaks more than one language and a child has, or may have, dyslexia, this study offers evidence against the widespread advice to drop the home language.

It is important to be precise about what the study does not show. It cannot tell us that bilingualism helps dyslexia. The reading-speed result points that way, but it is a single incidental finding from one study and should not be leant on. Nor is this a study of cause and effect in any direced sense; it compares existing groups of children at one point in time. And the language matters. Italian has a simple, regular sound structure, which the authors themselves say may be why bilingual children caught up so easily. Findings in Italian will not transfer automatically to English, whose spelling is far less consistent. A child learning to read in English may face a steeper climb regardless of how many languages are spoken at home.

The authors are candid about the study’s limits. The typically developing bilingual group in the first study was small, just 25 children across two language backgrounds. And in the second study the bilingual children came from a mix of first languages rather than one, which the researchers note as a weakness. They call for larger studies with bilingual children who share a single first language before the conclusion can be considered settled. This is one careful study, not the last word.

There is a practical point the authors stress that deserves weight. Phonological difficulties can be spotted early, before formal reading has broken down, and they are the same signal in bilingual and monolingual children alike. That means a bilingual child’s home language should not be treated as the cause of a reading problem, nor as a reason to delay assessment. A child struggling with rhymes, nonsense words, or sound-swapping games is showing something worth investigating on its own terms.

So the sensible reading is a calm one. If you are raising a child in two languages, this evidence does not ask you to choose between them and your child’s reading. Keep the home language, which carries its own cognitive and cultural value, and watch the child’s grasp of sounds closely. If that grasp seems weak, seek a proper assessment early. The bilingualism is not the problem to solve; the phonology is the thing to watch.