Vowel Distribution and Neutralization in Lubukusu Verbs: A Positional Faithfulness Account

In a number of languages, prominent positions that are critical for word recognition and general language processing tend to tolerate more vowel contrasts and may resist neutralization than positions that are less prominent. Specifically, word initial, stressed and final syllables, roots, stems and long vowels, often resist alteration or neutralization. This is because these positions are psycholinguistically and phonetically privileged in lexical access, retrieval and processing. Vowels in such positions are faithful to their underlying form for contrast preservation, and as such, marked vowels may be allowed in such positions even when they are banned elsewhere. In this study, we examine verbal vowel distribution and neutralization in Lubukusu (Bantu, Kenya). The main objective was to assess the role of positional faithfulness constraints in militating against contrast neutralization in some position and not others. Data for the study was collected from four native speakers of Lubukusu who were purposefully sampled based on their native-speaker competence and intuition. The analysis followed Optimality Theory (Prince & Smolensky, 2004) conventions using universal constraints ranked in a language particular constraint hierarchy. The position-specific faithfulness constraints were ranked above general faithfulness and markedness constraints in the tableaux to protect vowels in privileged positions from being neutralized. From the findings, it is observed that positional faithfulness constraints favour the preservation of underlying lexical contrasts in prominent positions. In these positions, a large number of vowels (including marked ones) are allowed to facilitate the perception of contrast that is key in both lexical access and retrieval, besides enhancing general language processing. However, neutralization of vowel contrasts may result in the marked vowels being restricted to non-root initial positions. This is only possible in a constraint-based phonology that ranks positional faithfulness constraints higher than the markedness constraints that restricts the marked vowels. The findings reveal that all vowels freely occur in the privileged positions, however, the so called ‘marked’ vowels (mid [e] and [o]) are neutralized outside such positions.