The general questions to be considered in this project are: how and why does sound change arise from the everyday processes of spoken language communication? An answer to these questions requires understanding how speech sounds as an abstract code that differentiates lexical meaning are related to the biological and physical principles that constrain the way in which they are transmitted between a speaker and listener in time. The specific model to be tested here is one in which sound change is triggered when listeners incorrectly associate or parse acoustic cues in the speech signal with the speech sounds intended by the speaker. In order to test this model, various physiological and perception experiments will be carried out to compare the different ways that speakers of the same community respond to sound-changes that are in progress. The principal long-term aim of the project is to understand how the stability and change of linguistic (in this case phonological) categories can be associated with, and possibly derived from, the mechanisms that control on-line processing in speech communication.
Speech is highly variable and context-dependent. Consider for example the /t/ in words like taub, Traube, Staub, and mitmachen. Although /t/ is functionally equivalent in these words, their phonetic characteristics are markedly different. Thus, the unaspirated /t/ in Staub is acoustically closer to /d/ of Daumen than to /t/ in any of these other words. Also, the /t/ of mitmachen, which is in a prosodically weak position, may be produced either as a glottal stop or possibly as a [p] (thus mipmachen). These types of modifications are the norm rather than the exception in spontaneous speech. Thus, the first word of guten morgen is almost never produced with two vowels, but much more commonly as gupm or even gum or gm.
The modifications due to context are typically much more severe than this. Thus as Hawkins (2003) shows, the production of English I don’t know can be, and often is, reduced to little more than a long nasalised vowel with intonational modulations to suggest that there are three syllables possibly accompanied by head-shaking to indicate negation: a listener nevertheless identifies this vastly compressed form of speech not only from the acoustic information, but also from the situational context.
The main relevance of these types of spontaneous speech phenomena to the present proposal is that they also condition sound change. Thus evidently the synchronic deletion, reduction, and lenition of consonants and vowels can produce radical extreme forms of diachronic change: consider as an example the present-day pronunciation of a town near Chester in England, Cholmondeley, whose spelling fossilises the Middle English pronunciation corresponding to Cholmund’s Lea (Kohler, 2001).
Our concern in the present proposal is not to describe such relationships between synchronic variation and diachronic change, but instead to explain how sound change can arise from the physiological, acoustic, and perceptual mechanisms that underlie the com-munication of speech between a speaker and hearer. One of our main goals in this regard is to test a model based on Ohala (2005), in which certain kinds of sound change are pre-sumed to arise in the ear of the listener (rather than in the mouth of the speaker) because of a perceptual misparsing of coarticulation. The empirical evidence for a link between perception, coarticulation and sound change can be derived independently from experiments demonstrating that listeners compensate perceptually for the effects of coar-ticulation. For example, because the vowel in the production of man is coarticulated (produced simultaneously) with the surrounding nasal consonants, it is typically nasalised, thus [mãn]. When listeners compensate for coarticulation, they undo or reverse these coarticulatory processes: in this example, they parse the nasalisation with the surrounding consonants and consequently hear an oral vowel, i.e. /man/, even though phonetically the vowel is heavily nasalised.
As recent studies by Beddor et al. (2007) of American English and Thai have shown, listeners sometimes only partially compensate for coarticulation and it is this which can, in Ohala’s (2005) model, result in categorical sound change. For the previous example, listeners would not only hear the vowel in man as partially nasalised, they also interpret the nasalisation as intended by the speaker: that is, listeners incorrectly assume that na-salisation was part of the speaker’s phonological speech production plan, rather than a mechanical by-product of the vocal organs’ sluggishness in making the transition between nasal and oral sounds. It is this kind of parsing error by the listener that can, in Ohala’s (2005) model, be a catalyst for sound change, such as the development of nasal vowels in French from a sequence of an oral vowel and final nasal consonant in Latin (manus).
There are, however, a number of issues that are unresolved in Ohala’s model: in particular, how exactly does the misparsing of coarticulation by the listener cause speech production in the community to change? This is one of the main themes to be addressed in the present proposal: the basis for the empirical analysis are recent studies by Harrington et al (2008). Here the prediction is made that for certain kinds of sound change in progress, young and old members of the same speaking community should differ both in the perception and production of their coarticulatory patterns.
A second aim of the present proposal is to investigate the influence of prosodic prominence on the production and perception of sound change. In Germanic languages, words which are in prosodically weak positions are often produced with greater variability and greater coarticulatory overlap between speech sounds: that is, weak constituents tend to be hypoarticulated and produced with less clarity (Jacewicz et al. 2006). This is because weak constituents tend to be semantically predictable: that is, speakers do not need to produce prosodically weak parts of speech with such clarity, precisely because the listener can bring to bear top-down semantic and pragmatic information to predict what the speaker is about to say at these points of the utterance. It is also known that prosodically weak constituents are often prone to sound change (e.g. Beckman et al., 1992; Harrington et al. 2000). However, there are so far no studies that have examined whether the listener's misparsing of coarticulation discussed above is more likely in prosodically weak contexts. Specifically, it was suggested in the preceding paragraph that sound change takes place when phonetic nasalisation is erroneously interpreted by the listener as phonological, i.e. as part of the speaker’s speech production plan. The related, second main question to be addressed in this proposal is whether this type of erroneous parsing is more likely in prosodically weak contexts (such as in function words like in and on or in content words when they are predictable from the semantic context) than in prosodically strong and semantically unpredictable contexts.
Beckman, M., K. de Jong, S.-A. Jun, S.-H. Lee (1992) “The interaction of coarticulation and prosody in sound change”, Language and Speech 35, 45-58
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Ohala, J. (2005), “Phonetic explanations for sound patterns. Implications for grammars of competence”, in: W. Hardcastle, J. Beck, eds., A Figure of Speech. A Festschrift for John Laver. London: Erlbaum, 23-38.