A central claim of Optimality Theory (Prince and Smolensky 1993, McCarthy and Prince 1993a) is that phonological variation can be modeled through the variable ranking of universal constraints. In this thesis, I test this claim by examining variation in the tongue root vowel harmony system in a number of closely related yet distinct Bantu languages of Congo and Zaire. The twenty-odd languages are drawn from each of Guthrie 1967's eight Bantu C. subgroups and are shown to vary along a number of dimensions. One is morphological, related to whether or not the harmonic element in the lexical root extends to prefixes and suffixes. This variation is shown to follow from the variable ranking of constraints that seek to ALIGN the harmonic feature, [retracted tongue root] ([rtr]) with the edges of the morphological domains STEM and WORD. A second parameter of variation concerns the relationship between high vowels and [rtr]. A third dimension involves the interaction of [rtr] with the low vowel [a] under harmony. Here, three patterns involving (i) low vowel assimilation, (ii) low vowel opacity, or (iii) low vowel transparency under harmony are shown to follow from the variable ranking of a few constraints. A significant theme that emereges in the study is recognizing and characterizing the distinct morphological and phonological domain edges involved in vowel harmony. An important contribution of this study is in bringing to light a language family where phonological tongue height, in this case expressed by the feature [low], is shown to be incompatible with tongue root retraction, as expressed in the feature [rtr]. Although the gestures of tongue body lowering and tongue root retraction are sympathetic in the articulatory dimension and in their acoustic effect, they are seen to be phonologically hostile, in fact, because of the redundancy relation between them. This redundancy-based phonological incompatibility is implemented via licensing-failure: [low] fails to "license" [rtr] because lowness implies retraction (Ito, Mester and Padgett 1994).

A central claim of Optimality Theory (Prince and Smolensky 1993, McCarthy and Prince 1993a) is that phonological variation can be modeled through the variable ranking of universal constraints. In this thesis, I test this claim by examining variation in the tongue root vowel harmony system in a number of closely related yet distinct Bantu languages of Congo and Zaire. The twenty-odd languages are drawn from each of Guthrie 1967's eight Bantu C. subgroups and are shown to vary along a number of dimensions. One is morphological, related to whether or not the harmonic element in the lexical root extends to prefixes and suffixes. This variation is shown to follow from the variable ranking of constraints that seek to ALIGN the harmonic feature, [retracted tongue root] ([rtr]) with the edges of the morphological domains STEM and WORD. A second parameter of variation concerns the relationship between high vowels and [rtr]. A third dimension involves the interaction of [rtr] with the low vowel [a] under harmony. Here, three patterns involving (i) low vowel assimilation, (ii) low vowel opacity, or (iii) low vowel transparency under harmony are shown to follow from the variable ranking of a few constraints. A significant theme that emereges in the study is recognizing and characterizing the distinct morphological and phonological domain edges involved in vowel harmony. An important contribution of this study is in bringing to light a language family where phonological tongue height, in this case expressed by the feature [low], is shown to be incompatible with tongue root retraction, as expressed in the feature [rtr]. Although the gestures of tongue body lowering and tongue root retraction are sympathetic in the articulatory dimension and in their acoustic effect, they are seen to be phonologically hostile, in fact, because of the redundancy relation between them. This redundancy-based phonological incompatibility is implemented via licensing-failure: [low] fails to "license" [rtr] because lowness implies retraction (Ito, Mester and Padgett 1994). / Arts, Faculty of / Linguistics, Department of / Graduate