Published online by Cambridge University Press: 15 June 2016
We describe three vowel-harmony processes in Tommo So and their interaction with morphological structure. The verbal suffixes of Tommo So occur in a strict linear order, establishing a Kiparskian hierarchy of distance from the root. This distance is respected by all three harmony processes; they ‘peter out’, applying with lower frequency as distance from the root increases. The function relating application rate to distance is well fitted by families of sigmoid curves, declining in frequency from one to zero. We show that, assuming appropriate constraints, such functions are a direct consequence of Harmonic Grammar. The crucially conflicting constraints are Ident (violated just once by harmonised candidates) and a scalar version of Agree (violated one to seven times, based on closeness of the target to the root). We show that our model achieves a close fit to the data, while a variety of alternative models fail to do so.
We would like to thank Robert Daland, Abbie Hantgan, Jeffrey Heath, Kie Zuraw, audiences at the Linguistic Society of America, the Manchester Phonology Meeting, Academia Sinica, Dartmouth College and UCLA, and the anonymous reviewers and editors for Phonology for their help with this article; all remaining defects are the authors’ responsibility. We are also indebted to the Tommo So language consultants, who provided all of the data. We would also like to thank Joni Ricks and her colleagues at the Statistical Consulting Group of the UCLA Institute for Digital Research and Education for their guidance in preparing and interpreting the statistical tests reported here.
The materials used for all the tests (including the program code for the Monte Carlo simulation) are available as online supplementary materials at http://www.journals.cambridge.org/issue_Phonology/Vol33No01. This research was supported by a grant from the Fulbright Foundation and by grants BCS-0537435 and BCS-0853364 from the U.S. National Science Foundation.