Room to read: The effect of extra-large letter spacing and coloured overlays on reading speed and accuracy in adolescents with dyslexia

https://www.sciencedirect.com/science/article/abs/pii/S0891422221002146

Thirty-two dyslexic children were matched on age, verbal and non-verbal IQ with 27 children with no diagnosis of dyslexia. The average age of each group was 13 years.

Extra-large letter spacing significantly improved reading speed more substantially for the dyslexia group. In addition, extra-large letters significantly reduced the number of missed word errors made by the dyslexia group.

This research replicates the earlier findings about the benefit of large letter spacing on reading.

The effects of letter spacing and coloured overlays on reading speed and accuracy in adult dyslexia (Sjoblom, Eaton, Stagg, 2016) https://pubmed.ncbi.nlm.nih.gov/27629067/> Zorzi et al. (2012, Proc. Natl. Acad. Sci. U.S.A., 109, 11455) found evidence that extra-large letter spacing aids children with dyslexia, but the evidence for the coloured overlays is contradictory (e.g., Henderson et al., 2013, J. Res. Special Educ. Needs, 13, 57; Wilkins, 2002, Ophthalmic Physiol. Opt., 22, 448), and possible combined advantages have not been identified. … Large letter spacing improves the reading speed in general, as well as improves the reading accuracy in dyslexic readers.

Extra-large letter spacing improves reading in dyslexia (Zorzi et al., 2012) https://pubmed.ncbi.nlm.nih.gov/22665803/ Although the causes of dyslexia are still debated, all researchers agree that the main challenge is to find ways that allow a child with dyslexia to read more words in less time, because reading more is undisputedly the most efficient intervention for dyslexia. Sophisticated training programs exist, but they typically target the component skills of reading, such as phonological awareness. After the component skills have improved, the main challenge remains (that is, reading deficits must be treated by reading more–a vicious circle for a dyslexic child).

Here, we show that a simple manipulation of letter spacing substantially improved text reading performance on the fly (without any training) in a large, unselected sample of Italian and French dyslexic children. Extra-large letter spacing helps reading, because dyslexics are abnormally affected by crowding, a perceptual phenomenon with detrimental effects on letter recognition that is modulated by the spacing between letters. Extra-large letter spacing may help to break the vicious circle by rendering the reading material more easily accessible.