Sound contrast difficult for babies at risk of dyslexia

One of the wonders of our language ability is that babies are born as universal listeners. That means they can hear all kinds of subtle speech differences, even if they are completely irrelevant in their native language. A well-known example is the contrast between the r and the l, which is missing in Japanese. Because mature native speakers of Japanese do not perceive contrast well, they have difficulty pronouncing these sounds when they speak English, for example. But Japanese babies can still hear that difference.

Babies are born as universal listeners.

A variety of research shows that the perception of babies during the first year of life changes from universal to language-specific. After all, it is in the interest of learning the native language to ignore traits that are not relevant to that language.

In children who later develop dyslexia, something seems to go wrong in this phase of language development. These children generally have more difficulty distinguishing speech sounds. Maartje de Klerk of Utrecht University investigated what happens in this phase of language development in babies with and without risk of dyslexia.


It may sound contradictory: babies taking part in a dyslexia study. Nevertheless, it is possible to detect babies with an increased risk of dyslexia, namely through their parents. This is because dyslexia is largely genetically determined. If at least one of the parents has dyslexia, then a child has a thirty to sixty percent chance of also developing reading and spelling problems. In that case one speaks of a ‘family risk of dyslexia’. If there is no dyslexia in the family, the chance is about four percent.

Maartje de Klerk for NEMO Kennislink

This study included 120 babies with and 120 babies without a familial risk of dyslexia, divided into three age groups: 6, 8 and 10 months. All test subjects came to the Babylab of Utrecht University. There the babies sat on a parent’s or caregiver’s lap while they looked at a screen. It always showed a smiling woman’s face, while different sounds were played. They were initially told a series of the same (non-existent) word, in which one vowel was central, such as ‘faap-faap-faap’. De Klerk: “When hearing such a sound sequence, a baby first looks very captivated at the accompanying image. But the moment the sound is fixed in his memory, he turns his head, Then it becomes too dull.” ‘Faap-faap’ makes for a big yawn!

Children tend to focus their attention on what is new. So when a sound is offered that sounds different, such as ‘feep’, the interest and thus the viewing time increases again. By measuring that viewing time, linguists can investigate whether a child actually hears a difference between, for example, ‘faap’ and ‘feep’. De Klerk not only looked at this Dutch sound contrast, but also at the difference between the English /æ/ of bad (bad) and the /ɛ/ of bed (bed). Because babies have a universal perception, it was expected that they could still distinguish that contrast by six months. When their hearing becomes more language-specific after that, it becomes more difficult. But this in turn benefits the contrast in their native language that they can hear better and better.

Merel van Goch’s PhD research previously showed that children who are good at recognizing sound contrasts in kindergarten, such as in ‘turnip’ and ‘raat’, score better in group 3 on various aspects of learning to read.

Anne Besselink for NEMO Kennislink

sound contrast

The research indeed shows that the children without risk of dyslexia became increasingly better at distinguishing the Dutch sound contrast. The risk group was also able to make this distinction between ‘ee’ and ‘aa’, but showed less improvement between six and ten months compared to the control group. This is in line with previous studies showing that children who develop dyslexia have difficulty distinguishing speech sounds.

The experiment with the English sound contrast showed a large difference between the two groups. While the control group did hear a sound contrast at six months, this was not the case in the risk group. The children at risk of dyslexia were not able to distinguish English sounds in any age group. “The first experiment with the native sounds ‘aa’ and ‘ee’ shows that they can distinguish speech contrasts”, explains De Klerk, “but if those sound contrasts become more subtle, as with the English è sounds, it no longer works. .”

lab situation

Something strange was going on in the children without risk of dyslexia. The expectation was that the control group would still hear the difference between the English è sounds at six months, but not after that. After all, their universal perception changes into a language-specific perception. What the researchers found was that the babies were still able to distinguish the English contrast at six months, not anymore at eight months, but again at ten months. The latter came as a surprise.

De Klerk suspects that the lab situation plays a role. “It is often said very firmly that universal perception declines sharply in the first year of life. My suspicion is that the discrimination of sounds that do not occur in the mother tongue decreases, but does not disappear. When perception is stimulated, as in this experiment, babies can still discern contrast. In the lab you measure what is possible, what children should essentially be able to do. It is a big step to translate a lab situation one-on-one to the real world.”

Variation between speakers

What exactly helped the ten-month-old babies in the lab experiment cannot be said with certainty, but it may be the speaker variation. The sound sequences in this experiment were spoken by different speakers. This speaker variation would give the children in the control group an extra key when ‘calculating’ the sound contrast. But apparently it doesn’t help children at risk of dyslexia to the same extent. According to De Klerk, there are now ‘cautious indications’ that this is the case, but further research is needed.

Difficulty distinguishing sounds that are close together at an early age therefore seems to be strongly linked to the risk of dyslexia. However, not all children with a familial risk actually develop dyslexia. “The fact that these groups were so easy to separate in the experiment indicates that distinguishing sound contrast in this earliest phase of language development is a risk factor for dyslexia,” says De Klerk. “But dyslexia, like many other developmental disorders, is a multifactorial disorder. This means that several factors play a role in whether or not it develops.”

Source: Kennislink by

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