Implicit Learning is Intact in Adult Developmental Dyslexic Readers: Evidence from the Serial Reaction Time Task and Artificial Grammar Learning

Previous research yielded equivocal results concerning implicit learning abilities of developmental dyslexic readers. These studies employed a sequence learning task that requires a motor response to each stimulus. However, implicit learning has been often studied using non-motor tasks. Thus, we investigated implicit learning capabilities of adult developmental dyslexic readers in two standard implicit learning paradigms differing in the involvement of the motor system, namely the serial response time task (SRTT) and artificial grammar learning (AGL). Twelve adult developmental dyslexic and twelve age- and sex- matched normal readers were tested. In the serial response time task (SRTT), participants are exposed to a structured display. Learning is measured by comparing response time (RT) to the structured sequence with RT to a random display. In the artificial grammar learning task (AGL), letter strings following a markovian finite state grammar are presented. In a subsequent test phase subjects have to judge new letter strings according to their grammaticality. Learning of the stimulus regularities was found in both tasks and for both groups of subjects. Furthermore, participants were unaware of the underlying stimulus construction principles. Dyslexic readers were unimpaired in SRTT as well as artificial grammar learning relative to normal readers. These findings show that implicit learning is intact in dyslexia. Intact implicit learning capabilities should be taken into account when designing training programs for developmental dyslexic readers. Research of JR (RU846-1/1) and TFM (various grants) is supported financially by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG).