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The International Dyslexia Association definition of dyslexia was updated 20 years ago and has been referenced frequently in research and practice. In this paper, researchers from the Florida Center for Reading Research consider the components of the definition and make recommendations for revisions. These include recognizing the persistence of word-reading, decoding, and spelling difficulties, acknowledging the multifactorial causal basis of dyslexia, clarifying exclusionary factors, and denoting comorbidity with other developmental disorders. It is also suggested that the academic and psychosocial consequences of dyslexia be highlighted to reinforce a preventive service delivery model. Lastly, the inclusion of dyslexia within a specific learning disability category is supported., (© 2024. The Author(s), under exclusive licence to The International Dyslexia Association.)

The orthographic choice (OC) task-requiring individuals to choose the correct spelling between a word and a pseudohomophone foil (e.g., goat vs. gote)-has been used as an outcome measure of orthographic learning and as a predictor of individual differences in word reading development. Some consider the OC task a measure of orthographic knowledge (e.g., Conrad, Harris, & Williams (Reading and Writing, 26(8), 1223-1239, 2013)), whereas others have suggested that the task measures a reader's familiarity with the word's orthographic representation and thus measures word reading skill (e.g., Castles & Nation, 2006). We examined this assertion by testing OC task performance of individuals ages 8 to 18 (J = 296) and their ability to read the OC target words (I = 80) in isolation using crossed random effects item-response models. Results reveal that response on the OC task is not fully determined by the ability of an individual to read the target word in isolation. Specifically, the probability of choosing the correct orthographic form when the word was pronounced incorrectly was .79; whereas it was .90 when the word was pronounced correctly. Measures of receptive spelling and phonemic awareness (person-characteristics) and word frequency and orthographic neighborhood size (item-characteristics) accounted for significant variance in orthographic choice after controlling for target item reading and other reading-related abilities. We interpret the results to suggest that the OC task taps both item-specific orthographic knowledge and more general orthographic knowledge.

Models of word reading that simultaneously take into account item-level and person-level fixed and random effects are broadly known as explanatory item response models (EIRM). Although many variants of the EIRM are available, the field has generally focused on the doubly explanatory model for modeling individual differences on item responses. Moreover, the historical application of the EIRM has been a Rasch version of the model where the item discrimination values are fixed at 1.0 and the random or fixed item effects only pertain to the item difficulties. The statistical literature has advanced to allow for more robust testing of observed or latent outcomes, as well as more flexible parameterizations of the EIRM. The purpose of the present study was to compare four types of Rasch-based EIRMs (i.e., doubly descriptive, person explanatory, item explanatory, doubly explanatory) and more broadly compare Rasch and 2PL EIRM when including person-level and item-level predictors. Results showed that not only was the error variance smaller in the unconditional 2PL EIRM compared to the Rasch EIRM due to including the item discrimination random effect, but that patterns of unique item-level explanatory variables differ between the two approaches. Results are interpreted within the context of what each statistical model affords to the opportunity for describing and explaining differences in word-level performance.

The purpose of this study was to identify important subject characteristics that predicted individual differences in responsiveness to word reading instruction in normally achieving and at-risk first grade children. This was accomplished by modeling individual word and nonword reading growth, and the correlates of change in these skills, in first grade students during two different phases of the school year. In the first phase of the study (October-January), word and nonword reading skill was modeled in normally achieving and at-risk children. Results of growth modeling indicated significant group differences in word and nonword reading growth parameters. A combination of phonemic awareness skill, advanced graphophoneme knowledge, and initial word/nonword reading skill predicted word and nonword reading growth in the control group, whereas, a combination of rapid naming speed, letter sound knowledge, and phonemic awareness skill predicted word and nonword reading growth in the at-risk group. In the second phase of the study (January-April), a subgroup of the at-risk subjects who exhibited limited growth in word reading skills during the first phase of the study was enrolled in 12 weeks of small group reading intervention designed to improve reading skills. Results of growth modeling indicated significant increases in word and nonword reading growth rates in this group during the intervention phase. Only rapid naming speed uniquely predicted word and nonword reading growth in the group of subjects receiving intervention.