Do children with developmental dyslexia have impairments in implicit learning?

We explored implicit learning in a group of typically developing and developmental dyslexic primary school children (9-12 y) using a modified artificial grammar learning task. Performance was calculated using two measures of performance: a perfect free recall (PFR) score and a grammaticality judgment score. Both groups of children required the same amount of exposure to memorize the items (i.e. PFR performance) (t((30))=1.620, p>0.05; p-value reported two-tailed). However, repeated measures ANOVA (Participant type x Grammaticality x Chunk strength) revealed a Participant type effect for grammaticality judgment scores (F((1,30))=4.521, p<0.05; p-value reported two-tailed). Typically developing children showed above chance performance in terms of both grammaticality and chunk strength of the stimuli. Children with developmental dyslexia on the other hand, failed to show implicit learning irrespective of the substring characteristics (i.e. grammaticality or chunk strength). We propose that children with developmental dyslexia may be impaired in their implicit rule abstraction mechanism, which can partially explain their persistent reading problems.