Machine Learning of Inflection

This chapter aims to introduce readers not familiar with computational modelling to some approaches and issues in the formal study of learnability, and the relevance of this field to theoretical linguistics and inflectional morphology in particular. After a general overview, the chapter highlights some of the obstacles in learning inflection. Inflection, considered separately from other components of language, is relatively restricted in its expressive power, which should make it easier to learn than syntax. However, inflectional systems are full of irregularities and mismatches between different levels of structure, and such irregularities make learning difficult. Overall, it is concluded that linguistically interesting proposals for machine learning of inflection should provide explanations for the nature and extent of irregularities and for the specific patterns of language acquisition and language change.

Verbal Inflection in Iha

Many studies of ‘alignment’ have appeared in the linguistics literature, both recent and in the past. One consistent theme in many studies is the desire to categorize, or ‘typologise’, a language by reference to labels such as ‘nominative’, ‘ergative’, ‘hierarchical’, etc. Even when different parts of the language are considered separately, descriptions such as ‘nominative-accusative verb agreement and ergative case marking’ are common. In this chapter we examine Iha, a language of western Papua New Guinea, and discover that we have a language which shows four different ‘alignment patterns’ on its verbs alone, proving that the only descriptively adequate typology must be one that critically examines languages in terms of component parts, and not just gross categorization.

Machine Translation

The goal of machine translation (MT) is to translate text from one natural language to another. Linguistic properties of the languages involved, and rich morphology in particular, play an important role in the difficulty of the task. After a brief survey of history of MT and morphologically rich languages (MRLs), the whole ‘MT pipeline’ is introduced, covering all the steps needed in the development of an MT system. The current mainstream approach, is highlighted, that is the phrase-based MT. The chapter the reader through the MT pipeline, explaining in detail how rich morphology negatively affects each of the steps, including the evaluation of MT quality. A wider range of MT system types is covered in the last section where old and contemporary methods for explicit and more linguistically adequate handling of rich morphology are surveyed.

Lithuanian Inflection

The chapter gives an overview of Lithuanian nominal and verbal inflection and discusses a number of contentious issues involving the demarcation of case and adposition, inflection and derivation, affix and clitic. The first issue is illustrated by the local cases of Old Lithuanian. These involve original postpositions added to case-marked forms. Lithuanian reflexive verb forms raise questions concerning the demarcation of clitics and affixes as well as that of inflection and derivation. A similar indeterminacy between proclitic and affix adheres to aspect, scope, and negation markers added to the verb. Baltic evidentials are an interesting instance of a syntactic phenomenon becoming morphologized and giving rise to an evidential paradigm. Finally, Lithuanian derivational aspect raises problems analogous to those of Slavic aspect, but these are made more complex by the weaker degree of grammaticalization of aspect in Lithuanian.

Inflection in Murrinh-Patha

This chapter discusses the complex inflectional system of Murrinh-Patha, a polysynthetic language of northern Australia, spoken by approximately 2500 people and still being acquired by children. Murrinh-Patha poses a number of interesting challenges for our understanding of inflectional morphology cross-linguistically, especially within the verbal domain. Although its verbal morphology is largely agglutinating, it is templatic and is rife with discontinuous dependencies, multiple exponence, and the interspersal of inflectional and derivational material. In addition, the verbal word is a complex predicate, built on a discontinuous stem, one part of which (the ‘classifier stem’) is taken from one of thirty eight largely fusional sub-paradigms exhibiting high degrees of suppletion, homophony, and irregularity. Furthermore, some of this verbal inflectional material is co-opted into the nominal system to derive nominal predicates raising interesting questions for the distinction between inflection and derivational morphology.

Modelling Inflectional Structure

The purpose of modelling inflectional structure computationally is addressed. It is a good way of checking analyses, and it provides external evidence for their validity. The development of a computational analysis can lead to the discovery of new generalizations about a language’s morphology. Finite state morphology and default inheritance methods are discussed. One question is whether morphological entities such as inflectional classes should be treated in terms of morphological features or whether they should be seen as emerging from the structure of the hierarchy or network. Both inflectional classes and stem classes can be treated as inheritance hierarchies. The issue of the different types of feature involved is raised again when deponency and syncretism are considered. Because it raises these issues, computational modelling allows for subtle distinctions in the treatment of a particular typological phenomenon, as well as providing a better understanding of the basic connections between related phenomena.

Inflectional Morphology in Language Acquisition

The acquisition of morphology is one of the major challenges in first language acquisition and the tasks children encounter vary to an extreme degree across different languages. The acquisition of morphological markers is presented from a cross-linguistic perspective with special focus on those characteristics of morphology which are relevant for acquisition. The chapter aims to give an overview of studies illuminating exactly this variation in a wide variety of typologically different languages. Special emphasis is placed on the interplay of individual grammars and learning strategies and on the question of whether morphological learning is better explained by the application of rules or rather by a step-by-step process of learning individual constructions, which are then generalized to more abstract schemas. A major challenge in acquisition studies is the question of how to determine productivity. The chapter presents some recent proposals in this domain, based on research on longitudinal corpora.

Inflection in Nen

Nen is a previously undescribed language of Southern New Guinea. It is an SOV language with ergative/absolutive case alignment and twelve distinct cases, a morphological split of intransitive verbs on a stative vs. dynamic basis, and verb morphology integrating prefixal and suffixal material to make a rich set of TAM distinctions as well as coding direction and person/number information for two arguments. It lacks verb chaining but has a rich set of non-finite constructions in which nominalized verbs are inflected for case, and a complex system of grammatical number, distinguishing up to four number values within some sub-parts of the inflectional system. It is notable for the extent that it exploits distributed, paradigmatic, and constructive/unificational architectures to give complete grammatical feature specifications. Verbs integrate information from prefix and suffix paradigms into a circumfixal paradigm for TAM, and actor and undergoer agreement. This chapter has a particular focus on verb morphology.

Contact-Induced Change

This chapter provides an overview of the borrowing of inflection. It is organized around two axes. On the one hand, it tackles the main question the process that allows for inflections to be taken over into about another language. This focuses on the dichotomy between isolated transfer of inflections, and transfer of inflections concomitant with other borrowing, for example as a side-effect of lexical borrowing. The second axis concerns the effect of the inflectional borrowing on the language: do the transferred elements introduce new categories—an addition to the old system—or are they parallel to or a substitution of pre-existing morphology?

The Morpheme

This chapter considers the nature and history of the notion of the morpheme in linguistic analysis, and the suitability of that concept to linguistic analysis. The historical origins of the term are traced, especially as it was used in American Structuralist work, and a range of problems with the literal application of the traditional concept to actual languages sketched. The role played by a notion of morpheme in a range of recent theories is then outlined. It is argued that although the re-emergence of an interest in morphology in the 1970s brought with it an assumption that morphemes of a classical sort are the fundamental building blocks of the structure of words, the facts of actual languages argue for a rather different conception of the relation between the form and content of words from that grounded in their division into units of this sort.