Phonology and phonetics — linked, but distinct: Evidence from dyslexia
Iris Berent, Vered Vaknin-Nusbaum & Albert Galaburda
(reviewers: Markus Pöchtrager, Chloe Marshall)
Abstract: A large phonological literature debates whether the phonological grammar is distinct from the phonetic system. Here, we address this question using evidence from developmental dyslexia.
Individuals with dyslexia are known to exhibit subtle auditory and phonetic impairments, but their linguistic phonological competence is spared (e.g., Berent, Vaknin-Nusbaum, Balaban, & Galaburda, 2012). This result is puzzling, as phonetics provides the building blocks of phonology (e.g., features). If the phonetic system is impaired, then how can phonological structure stand intact? We suggest that people with dyslexia compensate for their phonetic difficulties by over-relying on the phonological grammar. Our experiments gauge such top-down effects from phonology to phonetics. Participants—adult native Hebrew speakers—performed phonetic discrimination of a voicing contrast (e.g., pa-ba vs. pa-pa), embedded in novel tri-syllabic sequences (e.g., tapapa vs. patata). Our manipulation exploited the fact that ABB Hebrew stems favor identical over similar consonants (tapapa>tapaba), whereas BBA stems ban both forms (e.g., papata=pabata). Of interest is whether this phonological principle biases phonetic discrimination. Results from the dyslexia group showed that phonetic discrimination was strongly influenced by phonology. In particular, phonetic sensitivity (d’) was reduced when the ambiguous targets (BB) were embedded in well-formed ABB phonological sequences (e.g., tapapa) relative to ill-formed BBA ones (e.g., papata). Typical readers exhibited no such effect. A follow up experiment established that the context effect is not simply due to sequential ordering, as the cost for ABB sequences was eliminated once the context syllable (A) was replaced by its sine wave analog. These results show for the first time that adult individuals with dyslexia mitigate their auditory/phonetic difficulties by over-relying on their grammatical phonological knowledge. The resilience of phonology to perinatal sensory perturbations is in line with its view as a system of core knowledge. These results also contribute to the large body of evidence suggesting that phonology and phonetics are linked, but distinct .
Berent, Iris, Vaknin-Nusbaum, Vered & Galaburda, Albert. 2022. “Phonology and phonetics — linked, but distinct: Evidence from dyslexia”. Radical: A Journal of Phonology, 4, 491-527.