A native speaker knows how to produce an unlimited number of words and possible words in their language, which are related to each other by various semantic, phonological, and morphological properties. The production of an intended word is not independent of these relations: similar or associated words may influence speech processing and articulation in the short-term, and the cumulative effects may change the phonological forms of words in the long-term. Here, I present three studies investigating how such relations affect the acoustic durations of words, and how that interacts with phonological representation.

It is well-known that if a word can be easily predicted based on the surrounding words, it is likely to be produced in a shortened form. In the first study, I show that some words almost always occur in contexts where they can be easily predicted, and are thus almost always produced in a shortened form. Through two corpus experiments, I demonstrate that these lexical patterns affect the phonological forms of words over the long-term: words that are typically predictable on the basis of nearby words become permanently shortened, and are produced with a shortened form even when they are not predictable.

In the second study, I examine how competition with phonologically-similar words affects hyperarticulation strategies. In a web-based experiment, I find that when speakers need to communicate a word clearly, they may actually reduce the duration of parts of that word when doing so would increase the acoustic contrast with a contextually-relevant minimal-pair competitor. The result provides evidence about how speakers use implicit knowledge of lexical contrasts in hyperarticulation.

In the final study, I investigate a mechanism through which paradigms of morphologically-related words might interact with each other in speech production. Phonetic paradigm uniformity proposes that the articulation of a word is influenced by the articulatory plans of morphologically-related words. In a laboratory experiment, I demonstrate that there is evidence for this influence based on the durations of morphologically-distinct homophones like FREES and FREEZE. Over the long-term, these patterns may help explain categorical changes in phonological structure.

The overarching goal of this dissertation is to advance our understanding of linguistic tone and the role it plays in the organization of morphological systems. This topic is explored through a typological study, a case study, and a comparative study.

The first study presents a typology of tonal exponence, couched within an Abstractive Word-and-Paradigm approach to morphology. It builds on previous studies on exponence typology by extending it to the study of tone, and explores deviations from form-function isomorphism, polyfunctionality, morphomic distributions, paradigmatic layers, and inflectional class organization. It is argued that the attested diversity of form-function mappings constitutes an empirical argument for a paradigm-based view of morphology, where the range of encoding strategies are treated as equivalent, as opposed to choosing form-function isomorphism as the theoretical ‘ideal’.

The second study contributes to the documentation of tone and morphology in Tira (Heiban; Sudan), a previously understudied language. It is shown how tonal and non-tonal exponents interact in distinguishing verb forms in Tira. The system exhibits complexity of exponence in the sense that there is non-isomorphism between form and function; the meaning of the verb forms is distributed across different markers. It is argued that to understand the nature of the system, both the syntagmatic and the paradigmatic dimension need to be addressed, and an analysis is proposed by identifying a set of implicative relations, zones of interpredictability, and principal parts.

The third study is a comparative morphological study of the West Heiban languages Tira and Moro. It presents novel data illustrating subject and object marking on verbs in Tira and compares this to previously published works on Moro and the Central Heiban languages. Based on similarities and differences across the verb systems, Moro is argued to be innovative in several areas, and a series of diachronic developments are proposed to account for these facts. It is proposed that Moro has undergone a tonally conditioned constructional change whereby prefixed object markers became suffixes in verb forms associated with a specific tone pattern. This shows that tone may play an active role in language change and contribute to the reorganization of constructions.