Extending the Procedural Circuit Deficit Hypothesis to Late-Talking Toddlers: A Developmentally Plausible Framework

Background/Objectives: Late talking in toddlerhood is a heterogeneous developmental phenomenon, with most children catching up while a meaningful subset later develops developmental language disorder (DLD). Despite considerable interest in identifying early developmental mechanisms that contribute to persistent language difficulties, theoretical frameworks linking late talking to later DLD remain limited. The Procedural circuit Deficit Hypothesis (PDH) has been influential in interrogating DLD in preschool- and school-aged children, but its potential relevance to late-talking toddlers has received limited attention. This viewpoint paper argues that the PDH can be meaningfully extended to toddlerhood as a developmentally plausible framework for understanding early language delay. Perspective: In this viewpoint paper, we propose that the PDH may provide a developmentally plausible framework for understanding late talking in a subset of toddlers. Drawing on evidence from developmental neuroscience, motor development, statistical learning, and early communication studies, we argue that individual differences in procedural learning mechanisms emerge early in development and may contribute to variability in language outcomes. We further suggest that these early differences may represent one pathway linking late talking to later DLD. Implications: Extending the PDH to late-talking toddlers provides a mechanistic, developmentally continuous account of early language development, generates testable hypotheses for future longitudinal research, and highlights the potential value of examining procedural learning processes alongside traditional language measures. We emphasize that this proposal remains a theoretical extension that requires empirical evaluation and should be considered alongside alternative developmental pathways contributing to language difficulties. If supported by future research, this framework may help advance understanding of heterogeneity among late talkers and inform approaches to early identification and intervention.