Production and perception of the advanced tongue root vowel system in Ethiopian Komo

Komo [xom] is an endangered and under-documented language spoken along the Ethio-Sudanese border. This paper presents the results of the first phonetic investigation of the Komo vowel system and reports on a related perception experiment carried out in the field. Our first aim is to provide an acoustic description of the Advanced Tongue Root (ATR) feature in Komo, which is contrastive in the high vowels and allophonic in the non-high vowels. To this end, we present acoustic measurements of 2, 688 vowel tokens produced by 16 speakers. Our second aim is to examine the influence of Komo's typologically unique vowel harmony system on listeners' perception of the [ATR] feature. Komo ATR harmony displays two competing processes triggered by the high vowels (Otero, 2015): [ + ATR] spreads leftward to non-high vowels (e.g., /CaCi/ → [CəCi]), while [-ATR] spreads rightward to high vowels (e.g., /CɪCi/ → [CɪCɪ]). Sixteen Komo listeners and 16 native English-speaking controls performed an AX task with disyllabic (pseudo)words featuring context vowels and [±ATR] vowel continua. Patterns in the results suggest that (a) Komo listeners (but not controls) were influenced by the [ATR] value of the context, and (b) targets of [ + ATR] harmony were processed differently from targets of [-ATR] harmony.