Dagbani tongue-root harmony : a formal account with ultrasound investigation

The aim of this dissertation is (i) to contribute to understanding of [ATR] harmony patterns with a formal account of Dagbani [ATR] harmony using the theory of Headed Spans (Span Theory) and (ii) to answer basic empirical questions about the relations between tongue-root phonological features and the articulatory gestures involved in producing vowels with these features. In Dagbani [+ATR] harmony, there are three vowel triggers: the high front vowel /i/ triggers progressive assimilation of [+ATR]; the mid vowels [e] and [o] trigger regressive assimilation. Mid vowel triggers predictably surface in domain-final open syllables while /i/ is contrastive. I account for [+ATR] harmony using the theory of Grounded Phonology and the interaction of height-based markedness constraint hierarchies. In addition to the basic harmonic patterns, Dagbani [ATR] harmony is constrained by a height similarity condition limiting the trigger and target to vowels of the same specification for [±high]. Within Span Theory, this is argued to be a restriction on height featural combination in a [+ATR] span. A unique part of the formal analysis is the account of direction-specific consonant opacity. Having challenged previous harmony theories, the account here demonstrates the relative strength of Span Theory and supports the assumption that intervocalic consonants are targets of vowel harmony features. The second goal of the dissertation is achieved with an ultrasound imaging study testing the hypothesis that there is a direct mapping between tongue-root features and the articulatory positions of the tongue in producing vowels with different tongue-root feature specifications. It further investigates whether such a mapping also reflects which of the values of the feature [ATR]/[RTR] is dominant in a language. The results of 5 experiments show that in addition to the tongue-root position distinguishing [+ATR] from [-ATR] vowels, the dominant [+ATR] feature has a tongue-root position anterior to the neutral tongue-root rest position while the recessive [-ATR] vowels have a variable tongue-root position. The results support a direct mapping between the phonological feature [ATR] and the articulatory gestures that produce it.