My research interests lie in both phonology and phonetics: the study of the sounds of different languages both as tokens in an abstract system and as the physical movements of articulators resulting in soundwaves. A central focus of my research has been the extent to which the patterns that occur in the mind (phonology) may or may not be determined by what occurs in the vocal tract or the ears (phonetics). I am particularly concerned with the problem of the mapping between phonological features and articulatory gestures. My publications have examined from this point of view a number of casual speech reductions and assimilations in different languages: final-consonant deletion and palatalization in English, vowel assimilation in Italian and in the Nigerian language Igbo, palatalization in Russian, nasalization and voicing in Korean, and tone simplification in Thai.

• Perception of Thai tones in citation form and connected speech (with Rattima Nitisaroj, Georgetown University)

Abstract:  F0 contour shapes of the five tones of Thai differ from citation form to connected speech [Potisuk et al., Phonetica 54:22-42, 1997]. "Falling" tones have a rise-fall contour in citation, but may be realized as a rise in fluent speech. This study investigates whether Thai listeners can reliably distinguish tones in connected speech, and whether any cues to tone identity remain stable across contexts. In four experiments, ten Thai listeners identified naturally-produced and digitally-altered tones in a forced-choice task. In experiment one, listeners identified naturally-produced "falling" tones with 100% accuracy in citation forms and 96% accuracy in sentences, despite differing contours. In experiments 2-4 (replicating and extending Abramson [Lg&Sp 21:319-325, 1978], F0 onset and offset, peak height, and peak alignment were systematically modified on syllables in citation and sentence contexts. In all contexts, tones identified as high or low had an F0 peak or valley aligned to the right edge of the syllable. Mid tones had no F0 inflection. Tones identified as falling or rising necessarily had a pitch inflection at the syllable midpoint (end of the first mora). These findings support the view that tones are aligned with moras in Thai.

• What transfers? Word-integrity and assimilation in Korean/English interlanguage (with HK Kim)
 
Abstract:  Previous studies of L2 pronunciation have found a "word integrity" principle: learners tend to pronounce words separately, with no assimilation between them. This study investigates word integrity in Korean/English interlanguage, focusing on two cross-word boundary assimilations that apply in native Korean: nasal assimilation, a categorical phonological change, and voicing assimilation, a gradient phonetic effect. Sixteen Korean learners of English read English sentences where nasal assimilation or voicing assimilation was possible. The extent of nasalization and voicing in all tokens was measured Aword-integrity effect was not supported: both nasal assimilation and voicing assimilation were evident. However, voicing assimilation applied more often than nasal assimilation and there was a significant effect of level of instruction on nasal assimilation but not on voicing assimilation. These differences suggest that instruction can help learners overcome transfer errors involving categorical substitutions, but that routines of articulatory coordination, even across word boundaries, transfer more readily.

• The Lexical and Post-lexical Phonology of Thai Tones (with Bruce Morén, Center for Advanced Study in Theoretical Linguistics, University of Tromsø)
 
Abstract:  At first glance, the five tone system of Thai looks quite simple. However, we show that a detailed description of the phonological distributions of segments and tones combined with a careful examination of the phonetic realizations of duration and pitch in both citation forms and connected speech leads to the conclusion that the system is much more complex and interesting than is usually assumed. Based on data from an acoustic experiment, we claim that Thai is a mora-timed language with clear isochrony between moras and rhyme segments; that the tone bearing unit is the mora, not the syllable; and that previously unexplained restrictions on the distributions of tones in syllables closed by obstruents are the result of a relationship between the glottal feature and low tones. In addition, we describe and explain unexpected differences in the realization of tones in different phrasal positions in connected speech, and show that there are non-neutralizing contour tone simplifications that take place non-finally at the post-lexical level. This paper combines descriptive phonetics and phonology with both representational and constraint-based explanations to provide a unified account of the Thai tonal system. Our analysis supports a view of the grammar in which phonetics and phonology are separate, yet intricately related.
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• Syllables and Gestures in Florentine Vowel Assimilation (with Christina Villafaña, Georgetown University)

 
• Assimilation and Neutralization in Korean/English Interlanguage (with H.K. Kim)

 
• Articulatory Timing in a Second Language: Evidence from Russian and English
 
Abstract:  This study compares patterns of consonant-to-consonant timing at word boundaries in English and Russian, and investigates the roles of transfer and of the emergence of linguistic universals in second-language articulation. Native Russian speakers learning English and native English speakers learning Russian produced phrases in English and Russian contrasting VC#CV, VC#V, and V#CV sequences. The duration of all stop closures was measured, as was the percentage of C1#C2 sequences in which C1 was audibly released. Native Russian speakers speaking Russian had a higher percentage of released final consonants than did Native English speakers speaking English, and a higher ratio of sequence to singleton duration. Examination of the timing patterns across different clusters revealed different articulatory strategies for the two languages. The native Russian pattern transferred to L2 English, but the native English pattern did not transfer to L2 Russian. Evidence both for articulatory transfer, and for the emergence of a default pattern of articulation, characteristic of neither L1 nor L2, was found.