In very general terms, phonology is the study of both the representational and computational properties of human sound patterns. These issues have been the focus of descriptive, formal, typological, and experimental work. This dissertation draws on experimental and fieldwork data from vowel harmony in four Central Asian Turkic languages, Kyrgyz, Kazakh, Uyghur, and Uzbek, to examine the computational and representational nature of vowel harmony patterns.

One perennial computational question relates to the nature of phonological dependencies – how local must they be? In the dissertation I examine reported transparency in Uyghur backness harmony to evaluate previous analyses of transparent /i/ in the language. Results indicate that putatively transparent vowels actually undergo harmony, which in turn suggests that the analysis of Uyghur is computationally far simpler than previously thought. The dissertation also investigates the strictness with which locality is evaluated, comparing various proposals concerning the participation of consonants in vowel harmony, developing a more nuanced understanding of the interplay between phonetics and phonology that accounts for segment-intrinsic resistance to coarticulation in harmony.

In addition to locality, the dissertation examines the nature of phonological representations. Structuralist and Generative research has generally assumed that phonology manipulates abstract categorical variables, in contrast to the gradient variables that pervade phonetics. As an example, Zsiga (1997) argues that vowel harmony, in contrast to gradient phonetic assimilation, produces categorical alternations between target vowels whose output forms are indistinguishable from their triggering counterparts. Results from an acoustic study suggest that backness harmony in Kazakh and Uyghur produces output sounds that systematically differ from trigger vowel qualities, with the assimilatory effect of harmony gradiently petering out across the word. After comparing findings to plausible phonetic and phonological accounts, I argue that the best account of the data involves gradient phonology. Throughout the rest of the dissertation I develop the claim that phonology may be gradient, examining gradience in harmony from perceptual, formal, and typological perspectives.