Variation learning in phonology and morphosyntax

While variation occurs in both phonology and morphosyntax, phonological variation also includes phonetic variation motivated by articulatory or perceptual factors. While learning in both domains is subject to cognitive biases, phonological learning may also be biased by physical factors, which may enhance learnability of phonetically motivated alternations. This study aims to identify whether learning differs when children are exposed to phonological or morphosyntactic patterns with equal complexity. Cantonese-speaking children learned an artificial language involving rounding harmony, where unround [e] or round [o] harmonizes with the following noun, or gender agreement, with feminine and masculine allomorphs lo ~ le. Patterns applied variably in 67% of training items, or categorically. Children were tested on generalization to novel stems. In the categorical learning conditions, participants showed comparable rates of harmony/agreement. In the variable phonological learning conditions, application of harmony exceeded the rate of exposure in training, suggesting the influence of a bias toward phonetically grounded rounding harmony. In the variable morphosyntactic condition, participants applied agreement below the rate of exposure. This finding points to a qualitative difference between learning in the two domains, with phonological (but not morphosyntactic) learning influenced by substantive grounding.