Vowel Harmony and Cyclicity in Eastern Nilotic

0. Abstract Vowel harmony in the Eastern Nilotic languages Maasai (Tucker & Mpaayei 1955) and Turkana (Dimmendaal 1983) is dominant-recessive: a [+ATR] vowel in either a root or a suffix causes all other vowels in the word to become [+ATR]. The phonemic low vowel in both of these languages behaves differently depending on its position in the word relative to the source of [+ATR], a fact that has previously been accounted for by two directional [+ATR] spreading rules subject to distinct conditions (Archangeli & Pulleyblank 1994, Albert 1995). I propose instead that the distinction between these two directions of harmony is (indirectly) determined by the cycle, and that harmony is due to a single bidirectional mechanism. A cyclic account makes a number of nontrivial and restrictive predictions that a directional account does not. First, a grammar in which the conditions on the two directions of harmony are somehow reversed is predicted not to exist. Second, the cyclic account crucially depends on the indirect blocking of harmony by another process that respects the cycle, and so the absence of such a process entails the absence of a directional asymmetry. Third, a grammar in which harmony only operates in one direction and not the other is predicted not to exist. Finally, only the cyclic account can readily handle a set of additional facts in Turkana.