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Reading Development in Fragile X Syndrome

Reading Development in Fragile X Syndrome

The ability to read is critical to the success of individuals with learning disabilities, as it is linked with independence, job opportunities, and acceptance by others. Despite the importance of reading skills, until recently few research studies have focused on the reading abilities of individuals with fragile X syndrome, the particular skills that are important when learning to read for children with fragile X, or the best ways to teach reading to this group.. Below, we review findings from a series of studies from our research group that address reading development in individuals with fragile X syndrome (i.e., Adlof et al., 2015; Klusek et al., 2015; Brazendale et al., 2015).

What do we know about the literacy profile of fragile X syndrome?

Prior research has shown that individuals with fragile X syndrome show significant reading delays relative to what would be expected for their age. In our work, we have focused on comparing children with fragile X syndrome to younger, typically developing children who are of a similar mental age. By comparing the children with fragile X to children of a similar mental level, we could look for the relative areas of strength and weakness in reading skills. The aim of understanding this profile of reading skills in fragile X is so that support can be targeted in the areas of weakness and that the areas of strength can be used.

When we compared the boys with fragile X to the younger group of a similar mental age, we found that boys with fragile X syndrome had reading skills that were on par and in some cases better than what would be expected, given their mental age (though many were delayed for their chronological age; Klusek et al., 2015). The tasks where children with fragile X did as well as, or better than, expected for their mental age included: identifying letters and words and matching written sentences with pictures. These findings show that individuals with fragile X syndrome are capable of achieving reading skills at or beyond cognitive expectations. An important implication of this finding is that it should not be assumed that a child’s reading level will be limited by their IQ (this outdated practice, known as “cognitive referencing” is based on the assumption that a child’s language-related skills will not surpass their cognitive level. Our findings show that, in some cases, children with fragile X syndrome do attain a reading level that surpasses their cognitive level, and therefore IQ should not be a limiting factor when considering a child’s potential to learn to read).

We also found that phonological skills are a relative weakness for boys with fragile X syndrome. Phonological ability broadly refers to the ability to break down words into their different sounds, joining together different sounds to make words, or changing words in sounds to make new words. For example, clapping along to syllables in words or recognizing when words rhyme are phonological skills. In typically developing children, your phonological skills in early life strongly predict how well you will be able to read when you are older. In our research, we found that boys with fragile X syndrome performed less well on phonological tasks than would be expected given their mental-age (Klusek et al., 2015). However, when we tracked the boys’ phonological development over time, we found that they acquired new phonological skills at the same rate as the younger comparison children, who were of the same mental-age (Adlof et al., 2015). This suggests that although the boys with fragile X syndrome displayed a general weakness in phonological ability, these skills did develop as their mental-age developed. The mental age of the children with fragile X may develop more slowly than the comparison children, but these findings highlight that phonological skills can be gained, and should not be discounted as a result of having a diagnosis of fragile X. This underscores the importance of receiving good quality support to learn to read, so that each child can reach their potential.

What does this research tell us about reading interventions for children with fragile X syndrome?

The projects above showed us what the areas of strengths and weakness are in the reading skills of children with fragile X. The next step is to find the most effective ways to support children with fragile X to read.

Generally, children are taught to read using one of two broad approaches:

  • a phonological-based approach, which focuses on teaching children to recognize sounds and the links between sounds and letters. An advantage of this approach is that it provides children with the skills that they need to “sound out” new words, so that they can read words that they have not been explicitly taught.

  • a whole-word approach, focuses on teaching children to memorize complete words. This approach can be effective in teaching children to recognize a limited set of words, but it does not provide children with the skills that they need to read new, untaught words.

Currently, phonological-based approaches are widely accepted as the best practice for teaching children to read, including children with typical development as well as children who have reading and language difficulties (National Early Literacy Panel, 2009).

In the past, whole-word approaches were generally recommended for teaching children with developmental disabilities, such as children with Down syndrome and other intellectual disabilities. This recommendation represented an attempt to play to the child’s strengths, as children with developmental disabilities often have strong visual learning skills. However, we now have direct evidence from a number of intervention studies demonstrating that phonological-based approaches are effective for teaching children with developmental disabilities to read, even when these children have weak phonological abilities (see Brazendale et al., 2015, for a review).

But what about teaching reading to children with fragile X? Traditionally, it has been recommended that children with fragile X be taught to read using a whole word approach (e.g., National Fragile X Foundation Education Project, 2012). However, no research studies have directly compared the effectiveness of phonological versus whole-word interventions for children with fragile X syndrome, so it is difficult to say with certainty which approach is best suited for this group (and, there may not be a “one-size-fits-all” solution). The fact that evidence supports the use of phonological-based approaches with other disability groups suggests that phonic-based approaches may also be effective for teaching children with fragile X syndrome, even if this is an area of weakness. In our research, we found that the phonological skills of boys with fragile X syndrome predicted their later word-reading achievement, even considering and controlling for the boys’ cognitive level and initial reading skills (Adlof et al., 2015). This suggests that phonological skills may, specifically, lay the foundation for reading success for individuals with fragile X syndrome. This research highlights that phonological approaches should not be ruled out for children with fragile X syndrome, given that phonological skills appear to support reading development in children with fragile X syndrome, despite being an area of weakness. Because no research studies have compared reading interventions for children with fragile X syndrome, we don’t know definitively whether whole-word approaches, phonological approaches (or some combination of the two) will be most effective for helping children with fragile X syndrome to learn to read. The next steps will be to investigate whether there are effective ways of strengthening the phonological skills of people with fragile X, whether a phonological approach is more effective than other teaching approaches (such as, a whole word approach), and what effects these interventions have on children’s overall reading abilities. Another next step will be to study the reading profile of girls who have fragile X syndrome, as most research to date has focused on boys and it is unclear to what extent these findings may apply to girls.


Adlof, S., Klusek, J., Shinkareva, S., Mounts, M., Hatton, D., & Roberts, J. E. (2015). Phonological awareness and reading in boys with fragile X syndrome. Journal of Child Psychiatry and Psychology, 56, 30-39.

Brazendale, A., Adlof, S., Klusek, J., Roberts, J. E. (2015). Teaching reading to youth with fragile X syndrome: Should phonemic awareness and phonics instruction be used? Evidence Based Practice Briefs, 9, 47-61.

Klusek, J., Hunt, A. W., Mirrett, P. L., Hatton, D. D., Hooper, S. R., Roberts, J. E., & Bailey, D. B., Jr. (2015). Reading and phonological skills in boys with fragile X syndrome. Journal of Autism and Developmental Disorders, 45, 1699-1711.

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