Stagg, S. D., & Kiss, N. (2021). Room to read: The effect of extra-large letter spacing and coloured overlays on reading speed and accuracy in adolescents with dyslexia . Research in Developmental Disabilities , 119 (104065).

Journal Article

Stagg, S. D., & Kiss, N. (2021). Room to read: The effect of extra-large letter spacing and coloured overlays on reading speed and accuracy in adolescents with dyslexia. Research in Developmental Disabilities, 119(104065).


Colored lenses/overlays; Enlarged print (on paper); High school; International (non-U.S.); Layout/organization of test items; Learning disabilities; Middle school; No disability; Reading




Large-spaced text—with increased font size to 14-point font and increased line spacing and letter spacing—and color overlay selected by test-takers were provided separately as conditions on a reading test. A4-sized color overlays were provided with a choice of 10 colors (yellow, orange, magenta, pink, purple, sky blue, aqua blue, grass green, jade green, celery green). These test conditions were compared with standard text size (11.5-point font) without color overlays.


A total of 59 students from among Years 7–10 (U.K. grade level system; equivalent grades in the U.S. would be grades 6–9) participated. Students were recruited from six schools in Cambridgeshire, Hertfordshire and London in England. Participants with dyslexia (n=32) and with no disabilities including dyslexia (n=27) were matched for age and for verbal and nonverbal IQ. Demographic information was also reported, such as age range, average age, and gender. Pre-screening scores were collected for all participants on the Raven's Progressive Matrices Plus version (Raven, 2008) to determine non-verbal intelligence, and the British Picture Vocabulary Scale-II (BPVS-II; Dunn et al., 1997) for receptive language ability, in order to match the participant groups.

Dependent Variable

Applying the same process that Sjoblom et al. (2016) previously used, four separate testing conditions were assembled from two original texts from the continuous reading sections of the York Adult Assessment (Hatcher & Snowling, 2002) and th York Adult Assessment Battery Revised (Warmington et al., 2013). Each participant completed all four testing conditions; data were gathered for oral reading fluency, including speed and accuracy, based on oral reading errors. Reading errors included (a) missed or skipped words, (b) added words, (c) wrong words, and (d) mispronunciations. Group mean score differences were reported.


Students with dyslexia had significantly slower reading speed (142 syllables per minute) than students without disabilities (191 syllables per minute), and students with dyslexia made significantly more oral reading errors in terms of wrong words and mispronunciations. Students with dyslexia showed significantly improved average reading speed (by 13%) in the extra large letter spacing test condition. In comparison, students without disabilities improved in average reading speed by about two percent in the extra large letter spacing test condition. Also, in the increased spacing condition, students with dyslexia evidenced a significantly lower frequency of missed words; in contrast, students without disabilities showed no significant differences in oral reading errors between letter- and word-spacing conditions. The use of color overlays showed no significant benefits for either students with dyslexia or students without disabilities, in comparison with no overlays. Limitations of the study, implications for practice, and suggested areas for future research were presented.