Child acquisition of syntactic and phonological variation

Abstract

While categorical variation exists in both syntax (e.g., EModE do-support vs. V-to-I) and phonology (e.g., English /r/-deletion), phonological variation also encompasses subcategorical phonetic adjustments, with many categories occupying a continuous range of values (e.g., English /u/-fronting). Moreover, many phonological patterns are grounded in physiological properties, e.g., /ki/ → [tʃi] alternation, which is motivated by articulatory, acoustic, and perceptual factors (Keating & Lahiri, 1993; Guion, 1998; Butcher & Tabain, 2004) that enhance its learnability (Wilson, 2006). Thus, while learning in both domains is subject to cognitive biases, phonological learning may also be subject to bias from physical factors. Several studies have compared acquisition in the two domains through artificial language learning experiments. However, the tasks often differ in complexity (Ferdinand et al., 2019; Hudson Kam & Chang, 2009) or test different populations, e.g., English-speaking (Hudson Kam & Newport, 2009) vs. Cantonese-speaking childen (Do & Mooney 2021). We examine whether morphosyntactic and phonological learning differ when children learn artificial languages of equal complexity. Children were tested on generalization to 24 novel nouns. In categorical tasks, participants showed comparable rates of harmony/agreement (83.9% syntax; 83.4% phonology). In variable learning, the syntactic and phonological learning tasks diverge. In the variable phonological task, the application of harmony exceeded the rate of exposure in training (74% with 67% exposure), suggesting the influence of a naturalness bias whereby children prefer phonetically natural rounding harmony to phonetically unnatural disharmony. In the variable syntactic task, participants applied gender agreement below the rate of exposure (63% with 67% exposure). This finding points to a qualitative difference between learning in the two domains, with phonological learning influenced by substantive grounding.