Testing Rhythmic Abilities in Developmental Dyslexia: Is Internal Rhythm Generation Intact?

Rhythm processing deficits in developmental dyslexia (DD) span across different rhythmic subcomponents and are difficult to capture using one experimental paradigm. How are dyslexic deficits related to motor periodicity, i.e., the execution of repetitive actions while internally generating rhythm? The present experiment investigated rhythm production in DD by means of unprompted tapping paradigm, testing the hypothesis that the ability to internally generate rhythmic patterns may be impaired. The tasks involved tapping of isochronous sequences at a comfortable and a fast tempo and tapping of a free rhythm. Forty adolescents diagnosed with DD (with or without comorbid dyscalculia) participated, along with thirty typically developing control participants. A background questionnaire gathered information about participants’ prior music training. The data show that both dyslexic groups tapped faster than the typically developing participants at the comfortable tempo. We found no statistical differences between groups in fast isochronous tapping or in the free rhythm production tasks, irrespective of music training or the presence of dyscalculia. All participants favored regular rhythms when tapping a free rhythm, with a notable preference for isochrony. These results have theoretical and clinical implications for rhythm deficit hypotheses of DD.