Abstract Tuesday: A Taxometric Investigation of Developmental Dyslexia Subtypes

May 14th, 2013

O’Brien et al. (2012). A Taxometric Investigation of Developmental Dyslexia Subtypes. Dyslexia, 18, 16-39.


  • developmental dyslexia;
  • subtypes;
  • double deficit hypothesis;
  • taxometric analysis

Long-standing issues with the conceptualization, identification and subtyping of developmental dyslexia persist. This study takes an alternative approach to examine the heterogeneity of developmental dyslexia using taxometric classification techniques. These methods were used with a large sample of 671 children ages 6–8 who were diagnosed with severe reading disorders. Latent characteristics of the sample are assessed in regard to posited subtypes with phonological deficits and naming speed deficits, thus extending prior work by addressing whether these deficits embody separate classes of individuals. Findings support separate taxa of dyslexia with and without phonological deficits. Different latent structure for naming speed deficits was found depending on the definitional criterion used to define dyslexia. Non-phonologically based forms of dyslexia showed particular difficulty with naming speed and reading fluency.

Practitioner Points

  • Support for separate subtypes of dyslexia, with and without phonological deficits (PDs), indicates a need for different approaches to intervention.
  • A discrepancy-based criterion identifies more non-PD cases that may be missed with a response-to-intervention diagnosis.
  • Sound symbol correspondence and decoding measures may best distinguish cases of dyslexia with and without PDs.


For help with dyslexia on the Gold Coast and Tweed regions contact the Understanding Minds Dyslexia & Reading Difficulties Clinic .

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