Implicit sequence learning in dyslexia: a within-sequence comparison of first- and higher-order information.

The present study examines implicit sequence learning in adult dyslexics with a focus on comparing sequence transitions with different statistical complexities. Learning of a 12-item deterministic sequence was assessed in 12 dyslexic and 12 non-dyslexic university students. Both groups showed equivalent standard reaction time increments when the sequence was unexpectedly changed, suggesting that learning of the sequence took place. However, a novel analysis comparing transitions of differing complexity within the learning blocks indicated that dyslexic participants were impaired only for higher-order but not first-order sequence learning. No difference was found in the explicit awareness contribution between the two groups and this was found not to correlate with reaction time performance. This result suggests that statistical complexity of the sequence may account for intact and impaired learning performance in dyslexia.