Modelling Exemplar-Based Phonologization Robert Kirchner
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Modelling Exemplar-Based Phonologization Robert Kirchner Section I of this chapter presents several laboratory phonology studies of sound change and phonologization which compel a reexamination of standard assumptions about gradience and categoricality. Section II presents evidence of the incremental nature of sound change. In this section, we confront the implications of these results for standard phonological theory, and suggest a way forward. 1. W(h)ither phonology? At the nexus of phonetics-phonology interface and synchrony-diachrony issues lies the problem of phonologization, standardly conceived as a diachronic development whereby gradient phonetic patterns come to be reanalysed as patterns over symbolic representations (Hyman 1975). Renewed attention to phonologization, particularly in the Evolutionary Phonology framework of Blevins & Garrett (1998, 2004), has cast doubt on the very centrepiece of modern phonological theory, the markedness constraints of Optimality Theory. Simpler grammatical models are possible, the argument goes, if the phonological formalism need not concern itself with questions of typological markedness or phonetic naturalness, leaving that job to diachronic interaction with the phonetic component, which is needed in any case [as is argued in section I, but see my comments]. Consider a phonetically sensible rule such as k ➝ k ʲ /__{i,e}. Phonological systems tend to include rules like this, rather than, say, k ➝ m/__{i,e}, and the former is widely attested as a sound change, simply because it arises from phonologization of gradient coarticulation, whereas there is unlikely ever to be a pattern of phonetic variation between /k/ and an [m]-like allophone to serve as grist for reanalysis. A phonological markedness constraint favouring assimilatory dorsal fronting is therefore superfluous. The research programs of phonetically based Optimality Theory (e.g. Hayes, Kirchner & Steriade 2004), and Functional Phonology (Boersma 1998) though coming at this issue from the opposite direction – incorporating phonetics more tightly into phonological theory and analysis – seem, ironically, to confirm the Evolutionary Phonology verdict. Striking resemblances have been found, in every domain of phonological typology1, between the substance of well-attested phonological patterns and lower-level phonetic variation, which relate straightforwardly to phonetic considerations such as articulatory undershoot, gestural overlap, aerodynamics, auditory salience, etc., such that there appears to be no domain of pure phonological markedness, autonomous from phonetics. At this point, it is useful to remind ourselves exactly what work the phonology module (now divested of responsibility for markedness generalizations) does in this division of labour. The reason we speak of some patterns as being phonologized is that they display categoricalization and stabilization, which are difficult to account for in terms of purely phonetic factors. The notion of articulatory undershoot (Lindblom 1963), for example, can explain gradient vowel reduction, where the degree of centralization varies continuously with speech rate (and any other factors affecting articulatory 1 With the probable exception of metrical phonology, which seems to reflect a rhythmic cognitive faculty (cf. Tilsen 2009) distinct from articulatory and perceptual phonetic considerations. This rhythmic faculty, however, does not serve as example of autonomous phonological markedness, insofar as rhythm is found in many extra-linguistic domains of human (and animal) behaviour, such as limb movement. displacement/velocity). But it cannot, by itself, account for categorical reductions of the sort discussed by Crosswhite 2004, e.g. a distribution of vowels with a cluster of points around [ə ], and other clusters around full vowel values, but with few points in between (see generally Pierrehumbert 1994 on the instrumental interpretation of discrete versus gradient variation). Nor can phonetic factors such as undershoot explain why phonologized processes are conditioned by coarse phonetic context, particular relatively stable cues such as stress placement, rather than fine phonetic detail which may vary from token to token, such as precise vowel duration. In a typical categorical vowel reduction, for example, the [ə ] fails to revert to a full vowel even in slow, careful speech, when articulatory velocity considerations are less pressing. Both categoricalization of the variation and stabilization of the context can be accounted for by assuming that the phonologized reduction pattern is stated over a different level of representation from the gradient pattern. To answer the question posed in the previous paragraph: this is in fact the only work that phonology appears to be doing -- if by 'phonology' we mean a symbolic level of representation for sound patterns and its attendant theory -- and it does it by brute force. The observation of categorical and stable behaviour is obtained simply by stipulating that the structural descriptions of phonologized patterns are limited in reference to a small set of discrete, symbolic units. Moreover, this assumption does not come with any intrinsic account of how phonologization occurs. At some point, under this story, speakers reanalyse patterns of variation, from numeric to symbolic terms; but what mechanism induces this shift, and what factors in the original phonetic pattern is it sensitive to? And if phonologization is merely an arbitrary reassignment of a pattern from one level of representation to the other, why don't we observe this development in reverse: 'phoneticizations' of originally stable categorical patterns?2 Indeed, this standard view, on closer examination, encounters a number of immediate difficulties. How do we reconcile this abrupt shift from numeric to symbolic patterns, which the standard view presupposes, with the incremental nature of sound change, discussed in section II above? Moreover, is the distinction between phonetic and phonologized patterns really as clear-cut as the foregoing discussion implies? Phonologization might instead be a matter of degree, ranging from low-level, slightly speaker-controlled variation at one end of the spectrum, to categorical, stable, perhaps somewhat morphologically conditioned alternations at the other. The two-level assumption forces a choice between phonetic and phonological analyses of any given pattern, thereby precluding elegant treatments of partially phonologized patterns, cf. Pierrehumbert et al. 2000, Cohn 2006. As an example of the latter, consider consonant lenition in Florentine Italian (Giannelli & Savoia 1979, Kirchner 2004): • Voiceless stops, /g/, and affricates /tʃ / and /d ʒ / obligatorily lenite to continuants in 'weak position' (i.e. roughly intervocalic within an intonational phrase); • but the outcome of this lenition varies gradiently from close fricative to Ø, depending on place of articulation, speech rate and register; • additional consonants undergo various forms of lenition in weak position in faster/more casual speech; 2 The editors suggest that near mergers might represent such a case of phoneticization. Near mergers, however, involve blurring of a lexically conditioned distinction (in some or all contexts), not a contextually conditioned pattern of variation going from categorical to gradient application. Phoneticization, in my intended sense, would correspond to, e.g., a final devoicing alternation pattern which is categorical, perhaps neutralizing, at one stage of a language, and a variable, partial devoicing pattern, sensitive to fine phonetic detail, at the next stage. In all the controversy about incomplete neutralization in final devoicing (see e.g. Warner et al. 2004), no one has suggested a historical development from categorical to gradient application as the explanation. • and lenition expands beyond weak position in faster/more casual speech. The categorical aspects of this pattern, spirantization of voiceless stops, /g/, and the affricates, are just the tip (indeed, three separate tips) of an iceberg of quantitative phonetic variation. I suspect that partial phonologizations will prove, upon sufficiently close examination of patterns in a broad range of languages, to be the rule rather than the exception. To state the problem in another way: Pierrehumbert 1994 observes that virtually every case of gradient allophonic variation which phoneticians have investigated has proven to be, in some respects, language-specific (cf. discussion of Beddor 2007 and Beddor et al. 2007 in section I above). How do these gradient patterns arise? There must be some mechanism whereby purely physiologically determined (and therefore language-independent) patterns of variation come to be incrementally enhanced, in language-specific ways. (Such a mechanism is sketched in the remainder of this chapter.) Here the phonologization problem resurfaces in a slightly different guise; but in this case we cannot attribute the development of the pattern to a shift in level of representation, for this is all quantitative variation within the phonetic component. On the other hand, a model of this quantitative enhancement of low-level variation presumably could handle phonologization as well. Categoricality can be regarded merely as an advanced stage of enhancement, 'the discrete limit of [a] continuous process,” as Pierrehumbert et al. 2000 put it, without resort to a symbolic level of representation. In sum, the assumption of a symbolic phonological level of representation