Directional asymmetry in nasalization: a perceptual account

Abstract

In this paper, I conduct a typological study on contextual vowel nasalization to elucidate the directional asymmetry involved in the process. I show that carryover nasalization is the default and extensive form of phonetic coarticulation in many languages and that it often exceeds the degree of anticipatory nasalization as coarticulation. On the other hand, I also show that anticipatory nasalization occurs more frequently than carryover nasalization as a phonological assimilation process. Consequently, I conclude that the relevant directional asymmetry in contextual vowel nasalization does not involve one direction of nasalization having absolute ascendency over the other, but rather involves each direction of nasalization having different kinds of ascendancies at different levels of grammar. This mismatch between phonetic and phonological tendencies in contextual vowel nasalization is claimed to arise due to an asymmetry in perception: anticipatory nasalization is more easily perceived than carryover nasalization, rendering the extensive degree of anticipatory coarticulation unstable in nature. Therefore, languages will either opt to suppress anticipatory coarticulation below a certain threshold or opt to phonologize it into a more stable assimilation pattern. This perceptual hypothesis is validated by the result of an AXB perception experiment which shows that anticipatory coarticulation is more easily perceived than carryover coarticulation.