Authors: George K. Georgiou, Dalia Martinez, Ana Paula Alves Vieira & Kan Guo.
Publication: Annals of Dyslexia (Springer). Published: 12 March 2021 2021 | DOI: 10.1007/s11881-021-00220-6
The purpose of this meta-analysis was to examine if individuals with dyslexia (DYS) have a deficit in orthographic knowledge. We reviewed a total of 68 studies published between January 1990 and December 2019, representing a total of 7215 participants. There were 80 independent samples in the chronological-age (CA)-DYS comparison and 33 independent samples in the comparison between DYS and reading-level (RL) controls. A random-effects model analysis revealed a large effect size (Cohen’s d = 1.17) for the CA-DYS comparison and a small effect size (Cohen’s d = 0.18) for the RL-DYS comparison. In addition, we found significant heterogeneity in the effect sizes that was partly explained by the level of orthographic knowledge (effect sizes being higher for lexical than sub-lexical orthographic knowledge). These results suggest that individuals with dyslexia experience an orthographic knowledge deficit that is as large as that of phonological awareness and rapid automatized naming reported in previous meta-analyses.
Georgiou, G.K., Martinez, D., Vieira, A.P.A. et al. Is orthographic knowledge a strength or a weakness in individuals with dyslexia? Evidence from a meta-analysis. Ann. of Dyslexia (2021). https://doi.org/10.1007/s11881-021-00220-6
These findings suggest that individuals with dyslexia experience difficulties in a variety of reading-related skills when compared to their CA controls. This, in turn, provides support to multiple-deficit models of dyslexia …. In addition, our findings suggest that the difficulties in orthographic knowledge persist into adulthood (the effect size in the adult group was a large as the effect size in younger ages) and can be found across writing systems, despite the fact that orthographic knowledge is somewhat differently defined in non-alphabetic orthographies such as Chinese.
In view of the dual route theory of word reading …, our findings suggest that individuals with dyslexia experience significant difficulties accessing and using both routes in word reading.
The lack of significant effects of orthographic consistency was also unexpected in light of arguments that children in consistent orthographies (including children with dyslexia) rely mostly on small grain size units to read words correctly and fluently…. A possible explanation for this finding may relate to how children with dyslexia are selected in consistent orthographies (i.e., using speeded measures of reading).
Our findings have some important implications for assessment and intervention. Given that children and adults with dyslexia have a significant deficit in orthographic knowledge, researchers may consider including measures of orthographic knowledge when screening children for dyslexia. At the same time, researchers should explore ways to incorporate activities in orthographic knowledge in their intervention programs.