Atypical local perception precedence in preschooler poor readers

Impaired phonological processing is widely assumed to be a main cause of developmental dyslexia (DD). However, also visual magnocellular-dorsal (M-D) deficits are frequently shown in children with DD. In a longitudinal study, we measured, in preschooler children, the interference of global stimuli on the processing of local stimuli as well as the interference of local stimuli on the processing of global stimuli by using a variant of Navon task. After one year, we tested the reading abilities in the same sample. Preschooler good readers presented the typical global interference effect during local processing, whereas poor readers did not showed this effect, suggesting a global perception deficit. In contrast, poor readers showed a larger local interference effect during global processing in comparison to good readers. This results demonstrate that children that will present reading difficulties, had a pre-existent atypical local perception precedence, suggesting that visual M-D stream efficiency could play a specific role before reading acquisition.