Development of foveal crowding in typically developing children and children with developmental dyslexia.

Foveal crowding refers to the impaired recognition of a foveal stimulus due to the presence of adjacent flankers. Previous research has produced inconsistent results regarding the maturation of foveal crowding, either at ages 5-7 or remaining elevated from ages 5 to at least 11. We investigated this developmental trajectory using a specialized set of digit stimuli (Pelli fonts) tailored for measuring foveal crowding. We measured foveal crowding in preschoolers, school-age typically developing children, and school-age children with developmental dyslexia, as well as in a group of adults. The results show that foveal crowding decreases with age, reaching adult-like levels around 8 years among preschoolers and typically developing children. Furthermore, dyslexic children exhibited heightened foveal crowding compared to their typical peers by approximately the same amount, regardless of age and reading level. Notably, preschoolers exhibited the most pronounced foveal crowding effects with considerable individual variability: some displayed crowding similar to that of older typical children and adults, while others exhibited similar or even higher levels of crowding compared to dyslexic children. This large variability suggests that foveal crowding may have the potential to serve as an early indicator for identifying developmental dyslexia, a possibility that warrants further longitudinal investigation.