Extra-large letter spacing improves reading in dyslexia

July, 2012

Increasing the spacing between letters has been found to improve reading accuracy and speed in dyslexic children, with poorest readers benefiting most.

It’s generally agreed among researchers that the most efficient intervention for dyslexia is to get the child reading more — the challenge is to find ways that enable that. Training programs typically target specific component skills, which are all well and good but leave the essential problem untouched: the children still need to read more. A new study shows that a very simple manipulation substantially improves reading in a large, unselected group of dyslexic children.

The study involved 74 French and Italian children — the two groups enabling researchers to compare a transparent writing system (Italian) with a relatively opaque one (French). The children had to read 24 short, meaningful, but unrelated, sentences. The text was written in Times New Roman 14 point. Standard interletter spacing was compared to spacing increased by 2.5 points. Space between words and lines was also increased commensurately. Each child read the same sentences in two sessions, two weeks apart. In one session, standard spacing was used, and in the other, increased spacing. Order of the sessions was of course randomly assigned.

The idea behind this is that dyslexic readers seem to be particularly affected by crowding. Crowding — interference from flanking letters — mostly affects peripheral vision in normal adult readers, but has been shown to be a factor in central vision in school-aged children. Standard letter spacing appears to be optimal for skilled adult readers.

The study found that increased spacing improved accuracy in reading the text by a factor of two. Moreover, this group effect conceals substantial individual differences. Those who had the most difficulties with the text benefitted the most from the extra spacing.

Reading speed also increased. In this case, despite the 2-week interval, there was an order effect: those who read the normal text first were faster on the 2nd (spaced) reading, while those who read the spaced text first read the 2nd (normal) text at the same speed. Analysis that removed the effects of repetition found that spacing produced a speed improvement of about 0.3 syllables a second, which corresponds to the average improvement across an entire school year for Italian dyslexic children.

There was no difference between the Italian and French children, indicating that this manipulation works in both transparent (in which letters and sounds match) and opaque writing systems (like English).

Subsequent comparison of 30 of the Italian children (mean age 11) with younger normally-developing children (mean age 8) matched for reading level and IQ found that spacing benefited only the dyslexic children.

A further experiment involving some of the Italian dyslexic children compared the spaced condition with normal text that had the same line spacing as the spaced text. This confirmed that it was the letter spacing that was critical.

These findings point to a very simple way of giving dyslexic children the practice they need in reading without any training. It is not suggested that it replaces specific-skill training, but rather augments it.

Reference: 

[3017] Zorzi, M., Barbiero C., Facoetti A., Lonciari I., Carrozzi M., Montico M., et al. (2012).  Extra-large letter spacing improves reading in dyslexia. Proceedings of the National Academy of Sciences. 109(28), 11455 - 11459.

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