This article describes a novel approach to the computational modeling of reduplication. Reduplication is often treated as a stumbling block within finite-state treatments of morphology because they cannot adequately capture the productivity of unbounded copying (total reduplication) and because they cannot describe bounded copying (partial reduplication) without a large increase in the number of states. We provide a comprehensive typology of reduplicative processes and show that an understudied type of finite-state machine, 2-way deterministic finite-state transducers (2-way D-FSTs), captures virtually all of them. Furthermore, the 2-way D-FSTs have few states, are in practice easy to design and debug, and are linguistically motivated in terms of the transducer's origin semantics or segment alignment. Most of these processes, and their corresponding 2-way D-FSTs, are available in an online database of reduplication (RedTyp). We classify these 2way D-FSTs according to the concatenation of known subclasses of regular relations and show that the majority fall into the Concatenated Output Strictly Local (C-OSL) class. Other cases require higher subclasses but are still definable by 2-way D-FSTs.

This article describes a novel approach to the computational modeling of reduplication. Reduplication is a well-studied linguistic phenomenon. However, it is often treated as a stumbling block within finite-state treatments of morphology. Most finite-state implementations of computational morphology cannot adequately capture the productivity of unbounded copying in reduplication, nor can they adequately capture bounded copying. We show that an understudied type of finite-state machines, two-way finite-state transducers (2way FSTs), captures virtually all reduplicative processes, including total reduplication. 2-way FSTs can model reduplicative typology in a way which is convenient, easy to design and debug in practice, and linguisticallymotivated. By virtue of being finite-state, 2way FSTs are likewise incorporable into existing finite-state systems and programs. A small but representative typology of reduplicative processes is described in this article, alongside their corresponding 2-way FST models.

Languages are often categorized as having either predictable (fixed or quantity-sensitive) or non-predictable stress. Despite their name, fixed stress languages may have exceptions, so in fact, their stress does not always appear in the same position. Since predictability has been shown to affect certain speech phenomena, with additional or redundant acoustic cues being provided when the linguistic content is less predictable (e.g., Smooth Signal Redundancy Hypothesis), we investigate whether, and to what extent, the predictability of stress position affects the manifestation of stress in different languages. We examine the acoustic properties of stress in three languages classified as having fixed stress (Turkish, French, Armenian), with exceptions, and in one language with non-predictable-stress, Brazilian Portuguese. Specifically, we compare the manifestation of stress in the canonical stress (typically "fixed") position with its manifestation in the noncanonical (exceptional) position, where it would potentially be less predictable. We also compare these patterns with the manifestation of stress in Portuguese, in both the "default" penultimate and the less common final position. Our results show that stress is manifested quite similarly in canonical and non-canonical positions in the "fixed" stress languages and stress is most clearly produced when it is least predictable.

We demonstrate a computational restriction on iterative prosody in phonology by using logical transductions. We show that the typology is fundamentally local but requires output recursion, formulated via quantifier-free transductions and least-fixed-point operators, respectively. We focus on two case studies from iterative prosody. One is iterative secondary stress. The other is more complex: iterative syllabification and epenthesis in Arabic dialects. The second case study involves formalizing Ito (1989)'s analysis of directional syllabification.

We explore the generative capacity of morphological theories of reduplication. We computationally classify theories of reduplication using a hierarchy of string-to-string function classes. Reduplication as a process requires only the regular class of functions. We show that various morphological theories necessarily treat it as a more expressive polyregular function, while others maintain regularity. We discuss the significance of this formal result for reduplicative functions and recognition.