The contrastive hierarchy in phonology (review)

The concept 'contrast' is one of the most fundamental notions of phonology. This book focuses on two aspects of contrast: the ideas that only contrastive features are part of phonology, and that contrast is expressed by a language-specific hierarchy of features. Besides exploring theoretical hypotheses, the book extensively traces the development of ideas from Sapir to the present, and stands as the most significant work of scholarship on contrast in modern phonology. Indeed, the majority of the book concerns development of ideas leading to the author's theory, rather than isolated promulgation of that theory. The first sentence of the book establishes the guiding logic, quoting de Saussure: 'In a language there are only differences ... ', but modifying this by giving some status to phonetics, saying that 'a phoneme is identified not only by its positive characteristics ... but also by what it is not—that is, by the sounds that it contrasts with' (1). Under the approach of this book, the fact of being a linguistically distinct unit is the primary fact to be accounted for, and phonetic properties suggest particular features such as [nasal]. This distinguishes Dresher's theory from the traditional generative emphasis on phonetic description of language sound where contrast is epiphenomenal.

Given the complexity of the topic, it is unsurprising that certain aspects are not investigated much. D's treatment presupposes a determination of what the distinctive sounds (phonemes) of a language are, and accounts for how features are specified in phonemes. A reader in search of a definitive statement of the conditions for phoneme versus allophone status must resolve that matter elsewhere. D states, 'In all the examples that follow I will assume that we know what the contrasts are at this most basic level' (2). The central analytic question in this theory is which dimension for differentiating sounds is relevant, which means for a language having /i u/ determining whether these sounds contrast in terms of [back], [round], or both. D's central thesis is that phonetics alone does not determine the phonological analysis of sounds; thus, the phonetic qualities of /i e a o u/ in Czech and Slovak are the same, but the fact that Slovak also has /ä/ motivates different analyses of /a/ in the languages. Moreover, languages with the same contrastive vowel inventory— Czech and Russian—can have different featural treatments of that inventory.

The theory centers on the SUCCESSIVE DIVISION ALGORITHM (SDA), which uses feature ordering found especially in work by Roman Jakobson and Morris Halle. In each language, features are assigned in a language-particular order, termed a CONTRASTIVE HIERARCHY. The SDA assumes that the set of 'all sounds are allophones of a single undifferentiated phoneme', but 'if the set is found to consist of more than one contrasting member' (16), then following the feature order of the language, the feature divides the set into as many subsets as possible. This is repeated until every set has only one contrastive member. This computes a system of feature values for the phonemes, given a hierarchy and knowledge of which sounds are phonemes. In a language with the bilabial stop inventory /p b m/, if [voiced] is higher in the hierarchy than [nasal], then /p b m/ have analysis 1a, but if [nasal] is higher than [voiced], they have analysis 1b.

1. 1.

   a.	voiced > nasal			b.	nasal > voiced
   	p	b	m		p	b	m
   [voiced]	-	+	+		-	+
   [nasal]		-	+		-	-	+

In 1a, since /p b m/ are distinct, the set {p, b, m} is first partitioned into the [+voiced] subset {b, m} and the [-voiced] subset {p}. Since {p} contains one member, no further features are assigned, but {b, m} is further partitioned into the subsets [-nasal] {b} and [+nasal] {m}. Once /m/ is fully distinguished from /p b/ by [nasal], the feature [sonorant] may simply be irrelevant.

The second main claim of the book is the CONTRASTIVIST HYPOTHESIS, that 'The phonological component of a language L operates only on those features which are necessary to distinguish...