This study examines how speaking one language variety affects spelling in another. Classical theories predict that spelling develops from sound-based strategies in childhood to visual/memory-based strategies in adulthood, with phonological dependence disappearing as learners mature and are further exposed to literacy. We tested this with Jamaican Patois-English bidialectal speakers who systematically pronounce TH sounds (/θ/, /ð/) as /t/ and /d/.

We tested 93 participants (34 adults, 59 fourth-graders) on spelling words with TH sounds versus control words with T/D. Both groups showed substantial accuracy drops for TH words (adults: 76% vs 100% on controls; children: 40% vs 95%), with over 89% of errors being systematic T/D substitutions. Reading ability explained 66% of individual differences, while age added only 4% beyond reading skill. Children who explicitly recognized speaking two varieties performed better.

These findings challenge theories predicting that phonological interference disappears with development. Instead, when speakers’ home language differs from written standard, it persists throughout life. Though, it can be noted that adults manage interference more successfully than children. These results have implications for spelling theory and literacy instruction.

Bio: Tonia Williams is a Rhodes Scholar and DPhil candidate in Experimental Psychology at Oxford. Her research sits at the intersection of literacy development, cognition, and evidence-based education policy, with a current focus on her home nation of Jamaica. Her dissertation examines how Jamaican Patois–English bilingualism shapes cognitive and orthographic processing across the lifespan, challenging classical literacy theories and demonstrating how research with underrepresented linguistic communities advances the science of reading.
Tonia has presented at international linguistics and literacy conferences and authored policy analyses on literacy reform in The Jamaica Gleaner. Her prior work includes contributions to education research and equity, through J-PAL education, Harvard’s Laboratory of Developmental Studies, and several other international institutions. Her work bridges the lab and the real world and shows how rigorous developmental science can drive meaningful educational change.

Teams link: teams.microsoft.com/meet/3825967966058?p=oaa4boDA3tu5ZnqMja