The impact of the naturalness bias on vowel harmony patterns in transmission and communication

Abstract

There has been an ongoing debate about the extent to which phonetic naturalness shapes phonological grammar and might therefore lead to typological asymmetries. It is hypothesized that phonetic substance could bias phonological acquisition towards the more natural pattern, yet the experimental evidence for naturalness bias is inconsistent. Most previous work has studied the bias within a synchronic context with isolated learners, whereas the impact of the bias on diachronic changes and interaction among participants has hardly been considered. This thesis investigates the role of naturalness bias in two contexts, transmission and communication, with two artificial language learning experiments. The first experiment employed the iterated learning paradigm to compare the transmissions of two artificial languages exhibiting a natural pattern, vowel harmony, or the unnatural counterpart, vowel disharmony. Participants learned and passed down a miniature language to their successors in a sequential manner. Learners in the two conditions performed equally well, and the proportions of the two patterns showed a similar decreasing tendency over generations, suggesting no bias effect in the process of language transmission. The second experiment adopted the same language learning task and added a communication activity, where participants interacted using the learned language in pairs. After pure training, the two patterns were equally acquired, whereas during the interaction phase, the knowledge of vowel disharmony was negatively affected while vowel harmony was stably maintained. The distinctive performances of learning the two patterns support the existence of naturalness bias with the presence of interaction. The contrastive results of the two experiments prove the instability of the naturalness bias, in line with the past mixed findings. With novel focuses on transmission and communication, the thesis argues that diachronically, naturalness bias is not the only determining factor leading to the asymmetrical distribution of phonological patterns; In contrast, the bias surfaces particularly during the interactive process, highlighting the influence of communication on phonological grammar.