The Categorical Perception Deficit in Dyslexia: A Meta-Analysis

Speech perception in dyslexia is characterized by a categorical perception (CP) deficit, demonstrated by weaker discrimination of acoustic differences between phonemic categories in conjunction with better discrimination of acoustic differences within phonemic categories. We performed a meta-analysis of studies that examined the reliability of the CP deficit in dyslexia. The results show a reliable CP deficit in individuals with dyslexia compared to both chronological-age and reading-level controls. The CP deficit is stronger for discrimination than for identification, suggesting that the latter may only reveal between-category differences that do not fully reflect the CP deficit. The implications of these findings for the allophonic theory of dyslexia are discussed.