Visual-sequential and Visuo-spatial Skills in Dyslexia: Variations According to Language Comprehension and Mathematics Skills

This study focused on visual-sequential and visuo-spatial functions in a group of 39 heavily dyslexic children, compared to a Control group. Mean age was 12.72 (SD 1.71). The dyslexia group was divided into three subgroups by language comprehension and mathematics skills. Only on a visual-sequential task was no difference seen between the groups. The main differences occurred between the two dyslexic subgroups with no language comprehension impairment, but with varying mathematics skills. Whereas the subgroup with good mathematics skills scored within the upper ranges, the mathematics-impaired subgroup showed significantly lower scores. The third dyslexic subgroup, with both language comprehension and mathematics impairments, performed within the norm. The study indicates a dissociation between language comprehension and visuo-spatial skills in dyslexia, which has implications for how variations in dyslexia should be understood. The results also show that the visuo-spatial impairments seen in one of the dyslexia subgroups lead to two ways of understanding mathematics impairment when it co-occurs with dyslexia: (1) as a visuo-spatial problem; (2) as a linguistic problem. These distinctions should imply different intervention strategies in dyslexia.