Abstract:

Developmental dyslexia is the most common learning difficulty of written language with early signs from preschool age. Its main feature is the great heterogeneity of symptoms. The causes of the disorder can be identified both biologically and cognitively. The purpose of the present study was to investigate the neurocognitive nature of developmental dyslexia aiming to determine whether children with dyslexia can be divided into distinct subtypes based on their performance in various abilities and skills that have been related with developmental dyslexia. 101 students drawn from the 3rd, 4th, 5th and 6th grades participated in this study. All students had been diagnosed with dyslexia by an official public diagnostic center for special educational needs. Students were given a series of tests assessing a wide range of abilities and skills. Specifically, the phonological, memory and attention abilities, the processing speed, motor and visual-motor skills, and the visual perception were assessed. Cluster analysis revealed that children with dyslexia can be divided into three subgroups. The first subgroup consisted of children who were distinguished based on their performance in tests assessing the phonological, memory and attention abilities, the processing speed along with the visual perception and motor skills. The second subgroup consisted of children who were differentiated based on their performance in the areas of motor and visual-motor skills, as well as the memory abilities. The third subgroup consisted of children who were differentiated in their motor performance only. In conclusion, the findings of the study suggest that school-aged children accredited with developmental dyslexia can be distinguished into subgroups with particular neurocognitive characteristics. In addition, the results of the study support the current models regarding the existence of multiple neurocognitive deficits in developmental dyslexia as they showed that most students with dyslexia have difficulties in more than one cognitive domain.

Keywords:

Developmental dyslexia, neurocognitive subgroups, multiple-deficit.