Timing precision and rhythm in developmental dyslexia

Wolff, P.H. 2002. “Timing precision and rhythm in developmental dyslexia.” Reading and Writing, 15, 179–206.

Abstract

Current research on the etiology of developmental dyslexia is generally informed by either of two major hypotheses. One of these assumes that the phonological processing of consonants and vowels at a segmental level identifies the core deficit in developmental dyslexia and that it cannot be reduced to domain-general deficits of temporal information processing. The other hypothesis holds that phonological processing deficits are symptomatic of an underlying, domain-general dysfunction; and that at least some dyslexia subtypes are causally related to domain general deficits of temporal information processing for auditory and visual stimuli. This report starts from the assumption that the terms temporal information processing and phonological
processing as applied in current dyslexia research, are frequently conflated. Further, it assumes that the conflated terms must be decomposed into their concrete behavioral referents before the causal significance of either can be investigated systematically.

The studies to be summarized in this report represents one step toward such decomposition. The findings indicated that during a motor sequencing task, dyslexic students anticipated the signal of aniso chronic pacing metronome by intervals that were two or three times as long as those of age matched normal readers or normal adults.These group differences were significant when participants tapped with the preferred index finger alone or with both fingers in unison.Dyslexic students also took significantly longer than normal readers did to recalibrate their tapping responses when the metronome rate was experimentally changed in the middle of a trial.

In addition, dyslexic students, by contrast to normal readers, had inordinate difficulty reproducing simple motor rhythms by finger tapping, and similar difficulty reproducing the appropriate speech rhythm of linguistically neutral nonsense syllables.These difficulties were exaggerated when participants had to synchronize their performance to an external pacing
metronome.The implications of the findings for temporal information processing deficits on one hand,and impaired phonological processing on the other, are discussed.