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onsider the citation from Docherty and Foulkes (2001) which provides theepigraph of this thesis. Despite almost 20 years having passed since this statement was made, the numerous phonetic, phonological and dialectal descriptions of the English post-alveolar approximant/r/have failed to adequately account for its secondary articulation occurring at the lips. In his Dictionary of Phonetics and Phonology, Trask (2004) defines a secondary articulation as ‘any articulation which accompanies another (primary) articulation and which involves a less radical constriction than that primary articulation, such as labialisation or velarisation’ (p. 317). But for the case of English/r/, the lips may also be considered secondary in the more literal sense of the word in that they have attracted far less attention from linguists than the primary lingual articulation, and are thus overlooked in the literature. Indeed, as Docherty and Foulkes (2001) justly observe ‘if its labial component is mentioned at all, it is onlyen passant’ (p. 182, emphasis original). Most phonetic accounts simply state that/r/may involve lip rounding, particularly in word-initial position. But the phonetic implementation of this so-called lip rounding has yet to be described, which is somewhat ironic given the ease with which the lips may be viewed and measured during speech, contrary to articulations occurring inside the mouth, which require more sophisticated techniques to image and analyse.

Indeed, as well as contributing to the shape and size of the vocal tract, and thus to the

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acoustics of speech, the lips are a visible articulator in face-to-face communication. It has been shown countless times that speech perception may be influenced by what we see as well as by what we hear. For example, seeing a speaker’s lip movements may enhance speech com-prehension in adverse listening conditions by providing a complementary source of phonetic information to the auditory stream (e.g., Sumby & Pollack, 1954). However, seeing speech may not only enhance, but in some cases mayalterwhat the listener hears. The most famous and arguably most dramatic demonstration of the impact of visual speech cues on auditory speech perception is the McGurk Effect, in which conflicting auditory and visual speech cues are perceived as a fusion of the two modalities (McGurk & Macdonald, 1976). Speech perception is therefore influenced by information from multiple senses, and is thus defined asmultimodal. This thesis attempts to address the shortfall in the literature on English/r/by investigating the contribution of the lips to both its production and its perception in one particular variety of English, the non-rhotic English spoken in England, which we will refer to asAnglo-English. Just like the treatment of the lips, Anglo-English is also underrepresented in the phonetic literature on/r/. However, the lips may be particularly important to the production and perception of prevocalic/r/in this variety. This is because a change in progress is underway in which the post-alveolar lingual articulation for/r/is dropped/replaced for a labiodental one. Much of the fascination with the articulation of English/r/held by linguists the world over stems from the variation it entails, particularly in the large array of possible tongue shapes with which it may be produced. There is a (mis)conception that the lingual articulation of the post-alveolar Anglo-English/r/is less variable than in other varieties, despite a notable absence of empirical evidence. By considering the articulation of both the lips and tongue in this variety, as well as its perception in native speakers, we will not only dispute this claim, but will show that Anglo-English/r/warrants our attention, particularly regarding its labial articulation.

In a series of three experiments, we will show that the lips may enhance both the production and the perception of Anglo-English/r/. We find that speakers actively control the articulatory parameters available to them in order to enhance the perceptibility of/r/, including increased labiality. However, exposure to labiodental/r/without a lingual constriction has resulted in

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perceptual uncertainty in England, particularly due to the acoustic proximity of labiodental/r/

([V]) with labial-velar /w/. Listeners have to tolerate such a high degree of acoustic variation for/r/that even canonical productions of /w/ may be reconstructed as/r/in perception. We suggest that Anglo-English/r/has developed a specific labial gesture in order to increase its perceptibility in both the auditory and the visual domains. Perception data reveal that visual cues are moresalientthan the auditory ones for the/r/-/w/contrast in Anglo-English and that seeing the speaker’s lips may even override the auditory perception of the contrast. We conclude that in cases of auditory ambiguity, listeners may look to phonetic cues from the speaker’s face to better disambiguate the contrast, which may have sparked the change from a variable to a more generalised labial posture in lingual productions ofAnglo-English/r/. The results presented in this thesis therefore have theoretical implications for the nature of speech perception as a multimodal entity and we conclude that visual speech cues may play a role in the shaping of phonological sound systems.

This thesis is divided into three parts. InPart I, we review the existing literature which will serve as a background. InChapter 1, we focus our attention on audio-visual speech perception, notably the effect of seeing the speaker’s lip movements on the perception of spoken utterances.

We end the chapter by considering the implications of multimodal speech perception to what we know about how spoken language has evolved and how it may continue to evolve. In Chapter 2, we review the existing literature on the articulation of/r/in both rhotic and non-rhotic varieties of English. We examine the phonetic, physiological and sociolinguistic factors which may influence tongue shape, as well as provide an overview of the acoustics of/r/.

We end the chapter by considering the emergence of labiodental variants in Anglo-English.

InChapter 3, we study existing phonetic accounts of labialisation in consonants and vowels in a variety of languages. Our review of the literature will lead us to call into question the appropriateness of the termlip roundingin phonetic descriptions of vowels and consonants and we propose thatlabialisationis a more appropriate term. We endPart Iwith a presentation of the motivations for the present thesis, as well as the main research questions to arise from the literature review.

InPart II, we investigate the contribution of the lips to the production of Anglo-English /r/ in two experiments. Experiment 1, which is presented in Chapter 4, examines to what extent lip protrusion contributes to the production of /r/ by considering both hyper- and non-hyperarticulated productions of/r/. We present articulatory data from Ultrasound Tongue Imaging (UTI) and synchronised lip camera videos, as well as acoustic data. In Chapter 5, we present the results from Experiment 2, in which we compare the configuration of the lips for Anglo-English/r/and/w/from lip camera videos using a variety of measures including techniques from deep learning.

InPart III, we investigate the contribution of the lips to the perception of Anglo-English/r/.

In the final experiment of the thesis, Experiment 3, which is presented inChapter 6, we assess to what extent the labial gesture for/r/isperceptually salientin Anglo-English speakers by considering the perception of/r/and/w/in auditory-only, visual-only, congruous audio-visual and incongruous audio-visual modalities. We end this thesis with Chapter 7in which we present a general discussion of the results, their theoretical implications and possible future directions.

Part I

Background

Portions of this work were published in King, H. & Ferragne, E. (2020). Loose lips and tongue tips: The central role of the /r/-typical labial gesture in Anglo-English. Journal of Phonetics, 80, 100978.

doi:10.1016/j.wocn.2020.100978

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