Phonological variation and lexical representation in speech production : phonetic and psycholinguistic evidence on french schwa

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Thesis

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Phonological variation and lexical representation in speech production : phonetic and psycholinguistic evidence on french schwa

BUERKI FOSCHINI, Audrey Damaris

Abstract

Ce travail examine les mécanismes et représentations sous-jacents à la production de mots ayant plusieurs variantes de prononciation Un processus de variation phonologique est étudié en particulier: le schwa français. Les résultats d'études phonétiques et psycholinguistiques suggèrent que les variantes sans schwa ne résultent pas d'un processus de réduction phonétique de la voyelle ou d'une règle phonologique d'effacement. Ils montrent que les mots avec schwa ont deux représentations lexicales, une par variante. Cette conclusion s'applique aux mots dont les deux variantes sont utilisées ainsi qu'aux mots produits avec une seule variante dont la variante non utilisée correspond à l'orthographe du mot ou est fréquemment entendue dans le discours d'autrui. Les données suggèrent par ailleurs que les représentations lexicales utilisées en production sont abstraites. Ces résultats conduisent l'auteur à proposer un modèle psycholinguistique de la production des mots qui intègre les variantes de prononciation.

BUERKI FOSCHINI, Audrey Damaris. Phonological variation and lexical representation in speech production : phonetic and psycholinguistic evidence on french schwa. Thèse de doctorat : Univ. Genève, 2010, no. L. 697

URN : urn:nbn:ch:unige-128355

DOI : 10.13097/archive-ouverte/unige:12835

Available at:

http://archive-ouverte.unige.ch/unige:12835

Disclaimer: layout of this document may differ from the published version.

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PHONOLOGICAL VARIATION AND LEXICAL REPRESENTATIONS IN SPEECH PRODUCTION

Phonetic and Psycholinguistic Evidence on French Schwa

PhD Dissertation

Geneva, Switzerland, January 2010 by Audrey Bürki

Supervisors: Prof. Ulrich H. FRAUENFELDER, University of Geneva, Switzerland Prof. Ur SHLONSKY, University of Geneva, Switzerland

Jury: Dr François-Xavier ALARIO, University of Aix-Marseille, France Dr Mirjam ERNESTUS, Max Planck Institute for Psycholinguistics &

Radboud University, The Netherlands

Prof. Marina LAGANARO, University of Neuchâtel, Switzerland

Prof. Jacques MOESCHLER (president), University of Geneva, Switzerland

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La Faculté des lettres, sur le préavis d’une commission composée de Mesdames et Messieurs les professeur-e-s Jacques MOESCHLER, président du jury, Ur SHLONSKY, directeur de thèse, Ulrich FRAUENFELDER (FPSE, UNIGE) ; Dr. Xavier ALARIO (CNRS, Université d’Aix-Marseille) ; Marina LAGANARO (Université de Neuchâtel) ; Dr. Mirjam ERNESTUS (Max Planck institute for

Psycholinguistics & Radboud University, Nijmegen), autorise l’impression de la présente thèse, sans exprimer d’opinon sur les propositions qui y sont énoncées.

Genève, le 11 juin 2010

Le Doyen : Eric WEHRLI

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To my parents, Frédéric, and Jules

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ACKNOWLEDGEMENTS

This dissertation would not have been possible without the help, advice and support of many people.

First, I would like to express my gratitude to Uli Frauenfelder who supervised this work. He allowed me to follow my own path but guided me so that I didn’t get lost. Thank you for your trust, your precious advice. Thank you also for listening to my arguments, counter- arguments, questions, projects and frustrations. I learned a lot during these few years.

I would also like to thank my official main supervisor, Ur Shlonsky, whose role was mainly administrative, but essential. He is the one who administratively enabled me to conduct my PhD at the University of Geneva, and this means a lot. Since I was working on topics that were far removed from his research areas, he had to trust Uli and me completely, I am thankful to him that he did. His administrative advice, information and support were invaluable.

For his administrative role and support, I would also like to thank the president of my thesis committee, Jacques Moeschler.

My gratitude also goes to the three external members of my thesis committee. Every one of them played a special role during the past few years. When I first met Mirjam Ernestus, I was desperate to find a way to analyze my data in a way that would preserve the associations

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saved my research life. Many thanks for this Mirjam and for all the other things: your hospitality in Nijmegen (thanks to you I had the chance to visit the temple of Psycholinguistics), your advice on how to write an article and so on.

The next person I met was Marina Laganaro. I met her at the hospital shortly after having run my first experiment, using a DAT system with a click to record vocal responses. She introduced DMDX to me. Those who are familiar with production experiments will understand that without her, I would still be analyzing sound files. Some time later, she had her own laboratory in my hometown, which she kindly let me use so that I could have my family and friends perform a very long experiment (see Chapter V). I then used her laboratory again to perform two experiments, as I needed to have speakers from Neuchâtel rather than from Geneva. Thank you Marina for all this.

Finally, toward the end of my thesis, when I started thinking about an experiment which would compare the behavior of Swiss speakers with that of southern French speakers, Uli suggested that we seek advice from one of his friend, Xavier Alario. This turned out to be an excellent idea. Phone calls, long discussions, questions and one month at the University of Aix-Marseille followed (a great experience of French University culture, I must say, with strikes, evacuation because of gas leaks…). Many thanks Xavier; I learned a lot from this collaboration with you.

I would also like to thank the other researchers I had a chance to work with during these few years. Cécile Fougeron first, who taught me how to apply Jacqueline Vaissière’s classes on spectrogram reading to real data. She answered so many of my questions on phonetic or phonological matter. She introduced me to the research world: my first almost-missed submission deadlines, she listened to late-night rehearsals in her kitchen of the talk I was afraid of giving the next day. I am also glad I met Cédric Gendrot, who introduced me to my first programming language. This saved me (and still does) a lot of time. This did not go without questions and I thank him for his advice and answers. Finally, I also had the chance to work with Isabelle Racine, who shares my interest in the schwa. I hope that our work together will continue.

I would also like to thank my wonderful colleagues in Geneva. I started my PhD with two great persons: Irene Rotondi and Jennifer Martin. Irene, whose desk was just next to mine, is

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just the person you would like to have in your office. She always has a smile to give or a funny thing to say, whatever her mood; she is always willing to help; and she never complained about having such a messy colleague who kept losing her pens… As for Jenn, despite her own work she read most of the chapters of this dissertation and gave me her useful comments. I will miss our numerous statistical and non-statistical coffees and discussions. I would also like to thank Sophie Dufour, who was there when I started; she showed me where I could buy potato chips and answered all my beginner’s questions. She still does from time to time. As for Katia Iglesias and Julien Chanal, they were not my colleagues but had their office not too far away, and I often made extensive use of their statistical knowledge. I would also like to thank my short-term colleague Gaëlle Jardine, who corrected my English mistakes in Chapters I and V. Finally, I would like to thank Sandra Schwab for her friendship which started when we were colleagues in Neuchâtel and went on as we commuted from Neuchâtel to Geneva. She is someone I know I can always rely on, she will always find some time in her overfull agenda to read things for me.

The following persons also helped at some point and I would like to thank them: Manu Cuche who drew the pictures for Experiments 1 and 2, Guillaume Gravier and Philippe Boula de Mareüil who regularly answered my questions about automatic speech recognition systems, Pierre Lanchantin who did the same about speech synthesis systems, Jean-Marc Beltzung for his information on compensatory lengthening, Jean-Philippe Goldman for his version of aligner which allows for schwa to disappear, Odile Bagou, who was always available to discuss various matters around a coffee, Violaine Michel, who helped me in my quest for participants in Neuchâtel, Cyril Perret who read a few lines of this work and spent numerous hours discussing various matters and projects with me.

Logistically, I am indebted to Françoise, who let me use a room in her apartment in Geneva right next to the University, Paulette, who did the same in Marseille, Vero, Schouche, Clara, Mathilde, and Nikola for their hospitality in Paris. I would also like to thank all the participants who suffered my boring experiments. Especially my little sister, Johanie, who acted as a pilot-participant for most of my experiments, Magnarelle, Nanny, Samuel, Stéphanie D., Sarah, Joanne, Thierry, Anais, Fanny, Jean-Pierre, Didier, Lucas, Anne-Laure, Nathalie, Laurence, Céline, Michel, Rachel and Stéphanie K. for having taken part in the longer experiment.

Now in another world (the real one), I would like to thank my family and friends. For their understanding and their friendship. For still being there, even after so many “Sorry I can’t

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parents from whom I have learned the necessary curiosity and perseverance to start and achieve this work. I thank them also for taking care of Jules while I was writing the last lines of this work. Last but not least, I would like to thank Frédéric for having spent hours being a pilot participant in all my experiments, for having listened to rehearsals of talks for conferences and my first classes, for taking care of so many things while I was behind my computer, for coping with my bad moods, for listening to my enthusiastic, incomprehensible explanations, and so on. 344 pages would not be enough to list all the things I owe you.

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segments may be added, deleted or replaced by others. Understanding phonological variation is of crucial importance for several research fields. It is important for linguists, as any viable theory of phonology must be able to account for such linguistic facts. It is important for psycholinguists, whose models must explain how phonological variants are produced and recognized. Finally, it is important for automatic speech processing (ASP), especially automatic speech recognition and text to speech. If not accounted for, phonological variation can be detrimental to the performances of such systems (Strik & Cucchiarini, 1999; Adda- Decker, 2007).

It is only during the last 15 years that psycholinguistic studies of speech comprehension have gone beyond studying canonical speech and have begun to examine how listeners recognize non-canonical variants of words. Findings on assimilation (e.g., Gaskell & Marslen-Wilson, 1996, 2001; Snoeren, Segui & Hallé, 2008), nasal flap (e.g., Ranbom & Connine, 2007) or schwa (e.g., Connine, Ranbom & Patterson 2008; Kuijpers, van Donselaar & Cutler, 1996;

Racine & Grosjean, 2000, 2005; Spinelli & Gros-Balthazard, 2007) have provided a deeper

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understanding of the recognition of this everyday form of speech. For production, by way of contrast, a similar shift in research has not yet taken place.

The aim of this work is to fill this gap by examining the nature and content of lexical representations for words with several phonological variants and the psycholinguistic mechanisms underlying the production of these variants. In order to address such questions, we focus on the production of schwa words in French. Schwa words are words with two possible realizations, a schwa and a non-schwa variant. For instance, the word requin ‘shark’

is pronounced either with schwa (e.g., [k]) or without (e.g., [k]). The alternation between the schwa and the non-schwa variant is commonly referred to as schwa alternation or deletion.

This work is above all empirical. Making use of methods from empirical phonetics as well as psycholinguistics, we explore the mental lexicon, the production process and its output. Our main empirical questions will concern the way schwa words are represented in the lexicon (i.e., the number of representations and their nature), the nature and locus of the process leading to the production of two pronunciation variants for these words, and its time course.

Additional related questions will also be broached, such as the roles of contextual factors and usage in the production of phonological variants, the construction of lexical representations for novel schwa word, and the similarities between the production and the recognition processes in dealing with phonological variants.

Chapter I will lay the theoretical foundations of this work. Firstly, we will provide the readers with a definition and some examples of phonological variation, together with a discussion of the important questions which phonological variation raises in several research areas. We will then discuss more thoroughly one example of phonological variation: French schwa alternation. Following this section on French schwa, we will provide a review of the crucial features of important models of speech production and discuss the way they account (or do not account) for variation processes. In addition, several important issues with regard to our research questions will be mentioned. Finally, methodological issues related to the study of the production of phonological variants will be discussed.

In Chapter II, we will present two phonetic studies whose aim is to examine the output of the production process. We will look for empirical evidence on the nature of the schwa alternation process. We will ask the question whether schwa alternation is better accounted for by a gradient process of phonetic reduction or by a categorical process arising at an

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earlier stage of the production process. To do so, we will examine the acoustical properties of non-schwa variants and the variables conditioning schwa alternation and duration.

In Chapter III, we will examine the lexical representation(s) of alternating initial schwa words (i.e., words with a schwa in their initial syllable as in cheval ‘horse’, produced in their two variants by a given group of speakers). Three on-line experimental studies using picture and symbol naming with words in isolation or noun phrases will investigate whether these words are represented in the lexicon with one or more than one lexeme.

Chapter IV will be concerned with other word types. We will examine the production of medial schwa words (with a word-internal schwa which is not in the first syllable of the word as in casserole ‘pot’) in addition to that of initial schwa words. Furthermore, the behavior of alternating versus non-alternating schwa words (i.e., words always produced in one variant by a given group of speaker) will be compared. In order to do so, the pseudohomophone naming paradigm will be used and the behavior of speakers from different regional backgrounds will be tested. Four experiments, conducted in Switzerland and in the southern part of France, will be presented.

In Chapter V, we will first investigate further the production of alternating and non- alternating schwa words via the learning of novel words. We will examine the criteria leading to the acquisition of new representations for schwa words. In a second experiment, we will study the representations and psycholinguistic mechanisms underlying the recognition of novel schwa words.

In Chapter VI, we will seek further empirical data on the exact nature of lexical representations. This chapter will not be restricted to schwa words but will concern the representation(s) of any word. Two opposite views will be examined; an abstractionist conception of the lexicon, assuming one abstract representation per word or word variants, and an exemplarist conception of the lexicon, assuming many phonetically detailed representations for each word.

The last chapter of this work will consist in several concluding remarks. We will discuss the implications of our experimental results for models of speech production, and make theoretical proposals to modify these models in order for them to account for the production of canonical and non-canonical speech. The implications of our findings for phonological accounts of French schwa alternation will also be discussed. Finally the need to pursue the investigation will be advocated and several lines of research will be proposed.

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I.1 Introduction

This introductory chapter will lay the theoretical foundations of our empirical work, which will be presented in the following chapters. We will thus discuss important issues related to this work’s main research question, i.e., how the human cognitive system represents and produces phonological variation, in particular how it represents and produces French schwa words.

The next section of this chapter (section I.2.) will be dedicated to the phonological variation processes. We will provide a definition of these terms, as well as examples of such processes in French and in other languages. We will take this opportunity to highlight the important questions that phonological variation raises in several research areas: in automatic speech recognition, text to speech and in the psycholinguistic study of word recognition and word production processes.

Following this general description of phonological variation, section I.3. will be dedicated to schwa alternation in French. Our aim is not to provide an exhaustive review of the extensive linguistic literature on French schwa. We will briefly sketch the fundamental questions that this vowel has raised and summarize the answers found in the literature. We will be particularly interested in phonological accounts of the alternation process as well as in studies reporting the acoustic properties of the schwa vowel, the variables conditioning the alternation process, and the consequences of schwa alternation for the word recognition process.

In section I.4., the main features of the most important models of word production will be reviewed together with the way they account or do not account for variation processes.

Throughout this work, we will argue that a better understanding of French schwa, but also of the word production process, requires that phonological variation processes be considered in relation to what we know about the production process in general. In order to do so, we first have to understand how the different features and processing stages of the production process are considered in word production models.

Finally, section I.5. of this introductory chapter will be devoted to methodological issues.

We will briefly sketch the different empirical methods available to study the production of phonological variants. We will discuss the drawbacks and advantages of these methods as

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well as potential problems one may encounter in the empirical examination of the production of phonological variants.

I.2 Phonological variation

As mentioned above, words in connected speech exhibit considerable variation. Different types of variation have been described. A first distinction is usually drawn between predictable and unpredictable variation. Predictable or systematic variation relates to variation which follows contextual rules (e.g., Spinelli & Ferrand, 2005). This type of variation (referred to as “phonological variation” and found for instance in assimilation, French liaison, or French schwa alternation) is traditionally assumed to arise in the phonological component of the production process. In contrast, non-predictable variation is traditionally attributed to phonetic processes and arises as a consequence of differences between speakers (due for instance to differences in regional or socio-economic background, in anatomy or speaking habits) or may occur in the same speaker’s speech. It is indeed rather infrequent that a given speaker produces the same word twice identically, even within the same stretch of discourse. Types of speech, emotional status, speech rate, discursive importance or predictability of the word are some of the potential sources of intra-speaker variability.

In this work, we will be mostly interested in phonological variation. Phonological variation results in several pronunciation variants for a given word. These variants differ either in terms of the number of segments (through segment deletion or insertion) or in terms of the nature of a given segment (e.g., place of articulation, voicing, etc.). Many processes of phonological variation have been described in the literature, for several different languages.

Assimilation is an example of such a process. In assimilation, a given segment takes the acoustic properties of an adjacent segment in certain circumstances. For instance, in place assimilation in English, a coronal consonant may take the place of articulation of the following consonant when this consonant is a labial or velar consonant (e.g., wicked prank realized as [wkb pæk]). Similarly, in French, a process of voice assimilation may occur between two adjacent consonants of different voicing. For instance the word-final /b/ may become voiceless when followed by a voiceless consonant as in une robe sale ‘a dirty dress’, realized as [ynpsal].

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Another example of a phonological variation process is flapping in American English.

Speakers often “flap” /t/s between two vowels, as in, for example, pretty, which gives us [pri] rather than [prti] (see Pitt, Dilley & Tat, submitted). Another common flapping phenomenon is nasal flap in American English. Nasal flap ([]) occurs optionally word- internally when a /nt/ cluster is found between a stressed and an unstressed vowel (Ranbom

& Connine, 2007). For instance, the word gentle can be realized with a nasal flap and, sounds like [dl].

Assimilation and flapping both result in the modification of some features of a given segment. Other processes of phonological variation lead to pronunciation variants differing in terms of the presence/absence of a segment. French schwa alternation is an example of such a process. Schwa alternation is a well-known process not only in French, but also in English, where an unstressed vowel can be optionally deleted in two different environments.

A schwa can be deleted in the initial syllable of polysyllabic words when preceded by a consonant and followed by a stressed syllable (pre-stress schwa deletion, e.g., potato, realized as [ptet]). A schwa may also be deleted in the second syllable of trisyllabic words, when the syllable containing the schwa is preceded by a stressed syllable (post-stress schwa deletion, e.g., envelope, realized as [envlp], see for instance Patterson, LoCasto &

Connine, 2003).

Similarly, in Dutch, two processes involving schwa have been described (e.g., Booij, 1995).

In schwa epenthesis, a schwa may be inserted in non-homorganic consonant clusters (i.e., clusters whose consonants have different places of articulation) in coda positions (e.g., elf

‘eleven’, realized as [lf]). On the other hand, schwa deletion occurs when a Dutch word contains two consecutive syllables with a schwa. In such cases, the schwa in the first syllable can be deleted provided that the resulting consonant cluster is of the type “obstruent + liquid” (e.g., soepele ‘smooth’ realized as [supl]).

Another example of a phonological process leading to two variants characterized by the presence/absence of a segment is the liaison process in French. Liaison in French refers to the appearance of a consonant between two words when the second word starts with a vowel (Nguyen, Wauquier-Gravelines, Lancia & Tuller, 2007). For instance, the sequence grand ours ‘big bear’ is usually realized as [!atus], i.e., a [t] is inserted at the junction of the two words.

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As a consequence of these phonological variation processes, the production of words in connected speech is highly variable. This variability raises crucial questions for several research areas. These questions are discussed below.

I.2.1 Phonological variation and automatic speech processing

Pronunciation variation is one of the stumbling blocks of automatic speech processing (ASP), be it for automatic speech recognition or text to speech systems. Strik (1999) underlines that modeling pronunciation variation, whatever its type, has proved to reduce word error rates in automatic speech recognition to sometimes as much as 20%. However, he also stresses that “the right solutions have not been found yet (...) more fundamental research is needed to unravel what kind of pronunciation variation is present in spontaneous speech, both in qualitative and quantitative terms”.

Phonological variation is also likely to interfere with the performances of text to speech systems. Most only produce one single phonetic realization for a given word or sequence (Boula de Mareüil, 2007). In some cases, very simple linguistic rules are applied to decide which of two variants of a given word is produced, which means that some words are always realized in their variant form and others in their canonical form. This leads to potentially artificial outputs (Boula de Mareüil, 2007). Clearly, as in automatic speech recognition, the integration of more linguistic knowledge is necessary to produce natural realizations (Lacheret-Dujour, 1991).

I.2.2 Phonological variation and speech recognition / production processes

Speech recognition involves the mapping of acoustic-phonetic features extracted from the incoming signal onto a lexical representation. The question researchers have been trying to answer is how this mapping can take place despite the radical changes caused by phonological variation in the incoming signal. Several proposals have been made. Within the framework of generative phonology, in which it is assumed that each word is represented by one single abstract representation, some authors have proposed to account for the recognition of phonological variants through the existence of phonological inference processes (or compensation). The recognition system takes account of the phonological context in order to recover the underlying representation of the intended word that is behind the realized variant.

For instance, Gaskell and Marlsen-Wilson (1996) provide evidence that listeners infer the

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underlying representation (i.e., the non-assimilated form) when presented with completely assimilated forms in appropriate contexts (i.e., contexts which license the assimilation, see also Gaskell & Snoeren, 2008). A modelization of this process is found in Gaskell and colleagues (Gaskell, Hare & Marslen-Wilson, 1995; see also Gaskell, 2003). Their connectionist model learns to compensate for assimilation by being exposed to the conditions in which assimilation occurs. Recent research on voice assimilation in French also shows that listeners recover the words behind assimilated forms (Snoeren et al., 2008).

In the same vein, Spinelli and Gros-Balthazard’s (2007) results on French schwa suggest that the recognition of non-schwa variants involves the restoration of the underlying form (i.e., the schwa variant).

An alternative view within the generative framework is taken by Lahiri and colleagues (Lahiri & Marlsen-Wilson, 1991; Lahiri & Reetz, 2002). While lexical representations are still assumed to be abstract and unique, they may also be underspecified for some features.

For instance, in order to account for assimilation of coronal consonants, it is assumed that coronal segments are lexically underspecified for place of articulation.

A radically different approach is adopted by exemplarist models of speech perception (e.g., Goldinger, 1998; Johnson, 1997). These models assume that the lexicon contains detailed lexical representations of each encountered token (exemplars). Contrary to abstract models, no normalization of the speech signal need occur. The incoming signal is simply mapped onto the corresponding representation. Phonological variation is dealt with like any other form of variation, with different exemplars for different variants.

More recently, several authors have argued that hybrid models, i.e., models involving the storage of abstract information and phonetic details in the lexicon, could better account for the recognition of phonological variants. For instance, Connine and Pinnow (2006) suggest a model that allows for several abstract phonological representations to be stored, one for each phonological variant (see also Ranbom & Connine, 2007). For a more extensive discussion on hybrid models of speech comprehension and evidence of the presence of both abstract information and phonetic details in the recognition lexicon, see Ernestus (submitted) or Nguyen, Wauquier-Gravelines and Tuller (in press).

Contrary to the recognition of phonological variants, which has received a lot of attention in psycholinguistic research during the last 15 years, the processes underlying the production of these variants have not yet been investigated with psycholinguistic on-line methods. Our current knowledge of how words are represented in the lexicon and encoded during

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production comes from experiments using canonical word forms only. Existing psycholinguistic models of speech production that were conceived to account for these data cannot therefore, account for more natural forms of speech. What we know about phonological variants comes essentially from corpus analyses, acoustic and articulatory studies. While this latter research is crucial for describing the output of the production process, on-line experiments are needed in addition to inform us about the nature of the lexical representations of words with several variants, and about the mechanisms (including their time course) underlying the production of such variants. The aim of this work is precisely to provide such data, through the investigation of the phonological variants of French schwa words.While our observations will be restricted to this particular process, they will contribute to the construction of an overall knowledge about phonological variation processes in production. The following sub-section provides a short review of the linguistic literature related to French schwa.

I.3 French schwa

As mentioned above, this work focuses on one particular process of phonological variation:

French schwa alternation. Several reasons led us to select this particular process. Firstly, even though schwa alternation occurs primarily in connected speech, speakers, upon instruction, can easily produce the non-schwa variants in isolation. French schwa words therefore provide an excellent medium for the study of on-line production of phonological variants. Secondly, French schwa alternation is a rather frequent process. For instance, in the ILPho Lexicon (Boula de Mareüil et al., 2000) it affects one out of ten French words.

Finally, while French schwa is one of the most studied topics in the French phonological literature, there are surprisingly few empirical investigations, and many questions regarding this vowel remain unresolved.

French schwa is a far from homogeneous entity. Different types of schwa words are described in the linguistic literature. A first categorization distinguishes alternating from non-alternating schwa words. Alternating schwa words are realized with two variants, the schwa variant and the non-schwa variant. For instance, in standard¹ or Swiss² French the

1 In this dissertation, the terms “standard French” refer to the variety of French spoken in the Parisian area.

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word semaine ‘week’ is realized as [smn] or [smn]. Schwas in these words are said to be optional. Non-alternating schwa words, on the other hand, are always realized with the same variant. Schwas in these words are either obligatory, i.e., always realized (as in squelette

‘skeleton’ [sklt] and guenon ‘female monkey’ [!n] in standard or Swiss French), or forbidden, i.e., never realized (as in casserole ‘pot’ [kasl] in Swiss French, where the middle graphic “e” is never pronounced in connected speech).

While this distinction between alternating and non-alternating schwa words looks quite clear, the facts are more complicated as the inventory of alternating words is difficult to specify.

Dialectal, idiolectal, and sociolectal factors affect whether a word can be produced in two variants. For example, most Swiss French speakers will refer to Geneva as [nv], while most French speakers will always use the schwa variant [nv]. Important differences can also be found in standard versus southern French. In standard French, speakers will tend to use both variants for many words with a schwa in the first syllable (i.e., initial schwa words) but only the non-schwa variants for words with a schwa in a different position (see Jetchev, 1999; Lyche & Durand, 1996). In contrast, in southern French, most initial schwa words will tend to be produced in their schwa variant only (Eychenne, 2006; Durand, 2009) whereas words with a schwa in a different position are either always produced with the schwa, or alternating, depending on the sub-regions and populations (Eychenne, 2006; Durand &

Tarrier, 2003; Durand, 2009).

A second categorization of schwa words is usually made as a function of the position of schwa in the word. A first category comprises initial schwa words, i.e., polysyllabic words with a schwa in their initial syllable (as in cheval ‘horse’). The second category comprises medial schwa words, i.e., polysyllabic words with a word-internal schwa, not in the first syllable (as in casserole ‘pot’). An additional distinction within medial schwa words relates to the position of schwa with regard to morpheme boundaries: some schwas are morpheme- internal (e.g., casserole) and, others are located at a morpheme junction (as in brusquerie

‘rudeness’). The third category of schwa words comprises final schwa words, i.e., words whose schwa occurs in the last syllable of the word (as in brusque ‘rude’). Among final

2 Swiss French is very similar to standard French (Racine, Andreassen, Bühler & Bürki, 2009). According to our observations, however, for many words, non-schwa variants are usually more frequent in Swiss than in standard French.

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schwa words, schwas in clitics (as in je ‘I' or le ‘the’) are usually distinguished from all other final schwa words.

These categorizations of schwa words are not only descriptive. They are theoretically important, and the different sub-groups usually receive different treatments in phonological accounts. In the present work, we will be mostly concerned with alternating and non- alternating schwa words, with a schwa occurring word internally.

Following this general description of French schwa, we will now discuss four important issues surrounding the schwa vowel. Each of these issues is somehow related to our research questions (i.e., the nature of the lexical representations and psycholinguistic mechanisms underlying the alternation between schwa and non-schwa variants in speech production).

Starting with a brief summary of the main phonological accounts of the alternation process, we will go on to schwa’s acoustic properties and phonological status. We will then provide a short overview of the variables governing schwa alternation in connected speech. Finally, we will summarize the few psycholinguistic studies that examine the recognition of schwa words in French and other languages.

I.3.1 Phonological accounts of French schwa alternation

Schwa is a very popular topic in the French phonological literature. The number of articles providing possible phonological accounts of the alternation process is very large. The questions these articles attempt to answer concern the content of the underlying phonological representation (i.e., does it contain the schwa vowel, and if so, how should it be represented?) and the nature of the phonological mechanism governing the alternation between schwa and non-schwa variants. In some sense, these issues are very close to the questions we address in this work. Like phonologists, we would like to describe the nature of the lexical representation(s) for schwa words together with the underlying mechanism leading to the production of the two different outputs (or, in phonological terms, surface forms). However, in this work, we will attempt in addition to go beyond a description of the linguistic system and provide information about the cognitive processes at play.

In the history of phonology, the nature of the units of the sound system or the underlying representations of realized words were first discussed in the seminal book of Chomsky and Halle (1968) “Sound pattern of English” (SPE). SPE assumes a distinction between two levels of representation: underlying representations and surface representations (i.e., the

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realized forms). Changes between the two levels are thought to result from the application of derivational rules. These rules may transform the underlying representation by means of insertion, deletion, or modification of segments or features. SPE is thus also the start of a reflexion on French schwa involving representations and derivational rules. Until SPE, linguistic accounts of French schwa were mostly descriptive or prescriptive.

In the following sub-sections, we briefly describe the main proposals that have been made to account for schwa alternation in French. These sub-sections are organized and labelled according to the nature of the mechanism assumed to account for the alternation between schwa and non-schwa variants. Importantly, as discussed above, most authors agree on the fact that schwa is not a homogeneous entity: there are different types of schwa words and they should not receive a unified phonological account. Hence, the different accounts listed below do not necessary apply to all schwa words.

I.3.1.1 Phonological rule of deletion or similar accounts

The first author to provide an analysis of schwa alternation within the framework of SPE³ is Dell (1973, see Dell, 1985). According to this author, morpheme-internal schwas are always present in the underlying representation of words. Non-schwa variants are the result of a phonological rule of deletion. In order to explain the distribution of schwas in surface representations, Dell provides a set of about a dozen deletion rules, based on schwa position in the word and on the segmental context. Two examples of such rules are the following:

ə→Ø / § C__

: ə /

__#0

According to the rule INI, any schwa preceded by a single consonant may be optionally deleted. The application of the rule INI is immediately preceded by that of the obligatory rule INI-EX, which states that all schwas preceded and followed by an occlusive constitute an exception to the rule INI.

Similarly, Selkirk (1978) assumes that schwa is a phonemic vowel that is always present in the underlying representation and may be subject to deletion. Her account of schwa deletion, however, is in metrical terms. According to this author, syllables are grouped into feet. The

3 See Racine’s PhD. Dissertation (2008) for more details on the different phonological frameworks and the way they account for the schwa alternation process.

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French foot is composed of a single syllable but may be more complex,

a schwa is involved. A syllable with a schwa may join with the preceding syllable. Both syllables will then constitute a single foot. When schwa is the right

foot, and when this schwa is separated from the preceding vowel by only o schwa is deleted.

With the introduction of Autosegmental Phonology (Goldsmith, 197

the schwa vowel in the underlying representation became more complex. In SPE, phonological representations consist

Phonological representations in Autosegm

of a hierarchical organization of different tiers, representing different types of constituents (e.g., segments, syllables or CV constituents

different tiers. Figure 1 provides a the word bag in such a framework

Figure 1. Possible p

Within the framework of Autosegmental Phonology for schwa alternation: schwa as

(Jetchev 2003). Anderson (1982)

Selkirk, based on a deletion rule. However

but zero. An empty nucleus is assumed to be present in the lexical representations of the words that alternate between a schwa and a non

underlying representation of

nucleus. When realized, schwa is the phonetic interpretation of this empty nucleus. Schwa is French foot is composed of a single syllable but may be more complex,

a schwa is involved. A syllable with a schwa may join with the preceding syllable. Both syllables will then constitute a single foot. When schwa is the right-hand

foot, and when this schwa is separated from the preceding vowel by only o

With the introduction of Autosegmental Phonology (Goldsmith, 1976), the way to represent the schwa vowel in the underlying representation became more complex. In SPE, phonological representations consisted of a simple linear alignment of segments.

Phonological representations in Autosegmental Phonology are more complex

a hierarchical organization of different tiers, representing different types of constituents , segments, syllables or CV constituents). Association lines link the constituents on the

provides an illustration of a possible phonological representation framework.

Possible phonological representation of the word bag Autosegmental Phonology.

the framework of Autosegmental Phonology, two major proposals concur to account for schwa alternation: schwa as an empty nucleus versus schwa as

rson (1982), for instance, adopts a similar approach to that of Dell and ased on a deletion rule. However, the underlying value of the segment is not / but zero. An empty nucleus is assumed to be present in the lexical representations of the words that alternate between a schwa and a non-schwa form. Figure

underlying representation of the word renard ‘fox’, with schwa represented as an empty When realized, schwa is the phonetic interpretation of this empty nucleus. Schwa is

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French foot is composed of a single syllable but may be more complex, as for instance when a schwa is involved. A syllable with a schwa may join with the preceding syllable. Both hand member of a binary foot, and when this schwa is separated from the preceding vowel by only one consonant,

), the way to represent the schwa vowel in the underlying representation became more complex. In SPE, r alignment of segments.

ental Phonology are more complex: they consist a hierarchical organization of different tiers, representing different types of constituents Association lines link the constituents on the on of a possible phonological representation of

bag in

, two major proposals concur to account an empty nucleus versus schwa as a floating segment adopts a similar approach to that of Dell and the underlying value of the segment is not /œ/ but zero. An empty nucleus is assumed to be present in the lexical representations of the Figure 2 illustrates the represented as an empty When realized, schwa is the phonetic interpretation of this empty nucleus. Schwa is

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thus structurally present in the representation but with no designated content In the realization of a form witho

Figure 2. Illustration of the underlying

In Dell, Selkirk and Anderson’s accounts, the material corresponding to the the representation is completely del

alternative account. Schwa is also assumed to be present in the underlying representation and, as in Anderson’s analysis, it is considered to be

nucleus. However, here, this empty nucleus is never deleted. In non simply not phonetically manifest

epenthesis accounts while still assuming account is found in Rialland (1986): in non deleted, while the nucleus is maintained.

Several authors also account for schwa alternation through the existence

segment (e.g., Encrevé, 1988). In such accounts, schwa when optional is still present in the underlying representation, but differs from the other segments as it is not associated to the CV tier nor to the syllabic tier.

word renard ‘fox’ with schwa as a floating segment.

line between the nucleus corr

segmental tiers. Depending on whether the word is realized with or without its schwa, the association lines between tiers will differ. According to Encrevé (1988), this representation in terms of floating segment only holds for monosyllabic

‘the’, je ‘I’) or in the first syllable of polysyllabic words

words with an obligatory schwa, schwa is represented with a fixed rather than a floating segment. In words with a forbidden schwa, the rime and nucle

thus structurally present in the representation but with no designated content In the realization of a form without schwa, the empty nucleus is deleted.

of the underlying representation of the word renard with schwa as an empty nucleus.

In Dell, Selkirk and Anderson’s accounts, the material corresponding to the

the representation is completely deleted in non-schwa variants. Charette (1991) provides an alternative account. Schwa is also assumed to be present in the underlying representation

’s analysis, it is considered to be the phonetic interpretation of an empty nucleus. However, here, this empty nucleus is never deleted. In non-schwa variants, it is

mply not phonetically manifest. Charette’s account thus differs from both epenthesis accounts while still assuming a lexical representation with the schwa.

account is found in Rialland (1986): in non-schwa variants, only the segmental content is the nucleus is maintained.

count for schwa alternation through the existence

segment (e.g., Encrevé, 1988). In such accounts, schwa when optional is still present in the underlying representation, but differs from the other segments as it is not associated to the CV tier nor to the syllabic tier. Figure 3 provides an illustration of the representation of

‘fox’ with schwa as a floating segment. As can be seen, there is no association line between the nucleus corresponding to the first syllable and the syllabic or CV and Depending on whether the word is realized with or without its schwa, the association lines between tiers will differ. According to Encrevé (1988), this representation in terms of floating segment only holds for monosyllabic alternating schwa

‘I’) or in the first syllable of polysyllabic words (i.e., initial schwa words) words with an obligatory schwa, schwa is represented with a fixed rather than a floating segment. In words with a forbidden schwa, the rime and nucleus are floating but there is no thus structurally present in the representation but with no designated content assigned to it.

‘fox’

In Dell, Selkirk and Anderson’s accounts, the material corresponding to the schwa vowel in rette (1991) provides an alternative account. Schwa is also assumed to be present in the underlying representation phonetic interpretation of an empty schwa variants, it is rette’s account thus differs from both deletion and a lexical representation with the schwa. A similar schwa variants, only the segmental content is

count for schwa alternation through the existence of a floating segment (e.g., Encrevé, 1988). In such accounts, schwa when optional is still present in the underlying representation, but differs from the other segments as it is not associated to the ration of the representation of the As can be seen, there is no association sponding to the first syllable and the syllabic or CV and Depending on whether the word is realized with or without its schwa, the association lines between tiers will differ. According to Encrevé (1988), this representation alternating schwa words (e.g., le (i.e., initial schwa words). For words with an obligatory schwa, schwa is represented with a fixed rather than a floating us are floating but there is no

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segment (be it fixed or floating) for the schwa on the segmental tier. When the schwa is not realized, the rime stays empty

Figure 3. Illustration

Schwa alternation has also been interpreted in the framework of Optimality Theory (Prince

& Smolensky, 1993; McCarthy &

underlying representation to the surface form by means of a set of universal constraints, which are organized hierarchically. For instance Tranel (2000) posits that schwas are for the most part present in the underlying representation of words. A constraint is assumed, stipulating that a candidate without the phonetic realization of schwa is preferable to a candidate with its phonetic realization. However, depending on the position of this constraint in the list of constraints and in particular regarding constraints about syllabi

consonant clusters, schwa will or will not be realized. Interestingly, speech rate or register may influence the position of the schwa constraint in the hierarchy of constraints, explaining the variation related to these variables. While sc

representation, the non-schwa variant does not result from a deletion rule per se in such accounts.

I.3.1.2 Phonological rule of e

Some authors have proposed to account for schwa alternation with the re

an insertion rule. In such accounts, schwa is absent from the underlying representation and inserted through a phonological rule during the production process. As underlined by Côté and Morrison (2007), while the deletion accounts are

segment (be it fixed or floating) for the schwa on the segmental tier. When the schwa is not realized, the rime stays empty and is deleted.

Illustration of the underlying representation of the word renard with schwa as a floating segment.

Schwa alternation has also been interpreted in the framework of Optimality Theory (Prince

& Smolensky, 1993; McCarthy & Prince, 1993). In such a framework, one goes from the on to the surface form by means of a set of universal constraints, which are organized hierarchically. For instance Tranel (2000) posits that schwas are for the most part present in the underlying representation of words. A constraint is assumed, ng that a candidate without the phonetic realization of schwa is preferable to a candidate with its phonetic realization. However, depending on the position of this constraint in the list of constraints and in particular regarding constraints about syllabi

s, schwa will or will not be realized. Interestingly, speech rate or register may influence the position of the schwa constraint in the hierarchy of constraints, explaining the variation related to these variables. While schwa is present in the underlying schwa variant does not result from a deletion rule per se in such

Phonological rule of epenthesis or similar accounts

Some authors have proposed to account for schwa alternation with the re

an insertion rule. In such accounts, schwa is absent from the underlying representation and a phonological rule during the production process. As underlined by Côté and Morrison (2007), while the deletion accounts are more strongly associated with

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segment (be it fixed or floating) for the schwa on the segmental tier. When the schwa is not

renard ‘fox’

Schwa alternation has also been interpreted in the framework of Optimality Theory (Prince framework, one goes from the on to the surface form by means of a set of universal constraints, which are organized hierarchically. For instance Tranel (2000) posits that schwas are for the most part present in the underlying representation of words. A constraint is assumed, ng that a candidate without the phonetic realization of schwa is preferable to a candidate with its phonetic realization. However, depending on the position of this constraint in the list of constraints and in particular regarding constraints about syllabic structure and s, schwa will or will not be realized. Interestingly, speech rate or register may influence the position of the schwa constraint in the hierarchy of constraints, explaining hwa is present in the underlying schwa variant does not result from a deletion rule per se in such

Some authors have proposed to account for schwa alternation with the reverse process, i.e., an insertion rule. In such accounts, schwa is absent from the underlying representation and a phonological rule during the production process. As underlined by Côté more strongly associated with

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morpheme-internal schwas, epenthesis accounts have been proposed to account mainly for words with a schwa at a morpheme or a word junction.

Côté and Morrison (2007), for instance, provide evidence that schwas in clitics result from an epenthesis. The underlying representation of these words does not contain the schwa. It is inserted during the derivation of the surface representation. Tranel (1981), following others, assumes that schwas at word boundaries and before some derivational suffixes (e.g., “-ment”

as in correctement ‘correctly’) are also inserted through an insertion rule. According to this author, the same holds for final schwas in southern French. Finally, some authors also discuss the insertion account for final schwas in standard French (Walker, 1993; Jetchev, 2003).

I.3.1.3 Schwa: not a phoneme / allophony

According to Martinet (1969, 1972), given that its presence is predictable (determined by the three consonants rule, Grammont, 1914), schwa is not a phoneme (see also de Cornulier, 1975). Its presence/absence does not result from the speakers’ choice and its function is that of a “lubrifiant phonique”, i.e., an epenthetic vowel inserted to ease the production of otherwise hard to pronounce clusters. Martinet thus assumes that underlying consonants that may be followed by a schwa have two surface forms (i.e., allophones), the choice of the allophone depending on the phonological context. For instance, the phoneme /d/ will be produced with the variant [d] before a vowel but will be produced with the variant [d] between consonants.

I.3.1.4 Allomorphy

Jetchev (1999) discusses the case of internal schwas before some derivational suffixes (such as “-ment”). He notices that the rule of schwa insertion in these words is not phonologically conditioned and does not seem to apply systematically. He suggests that morphemes such as

“-ment” have two phonology-conditioned allomorphs, one with and one without the schwa (e.g., /ma/ and /ma/).

I.3.1.5 Schwa alternation as an overlap between surrounding consonants’ gestures

A radically different approach is taken by Smorodinsky (1998). This author interprets French schwa alternation within Articulatory Phonology (Browman & Goldstein, 1992). Within this framework, segment deletion is explained by a modification in the coordination between the successive gestures and/or a reduction in the gestural magnitude. In other words, when a

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segment is no longer present in the phonetic output, it is either hidden by the extreme overlap of the surrounding sounds and/or its gestures are extremely reduced in time and space. According to Smorodinsky, schwa alternation in French could be the result of an increase in gestural overlap in casual speech. The gestures for schwa would be hidden by the surrounding consonants’ gestures.

A similar proposal is made by Davidson (2006) to account for pre-stress schwa deletion in English (e.g., as in potato, realized as [ptet]). Davidson shows that non-schwa variants’

clusters show acoustic residues of the schwa vowel and concludes that schwa deletion does not lead to well-formed consonant clusters (i.e., these clusters differ from identical underlying clusters). For instance, she finds a longer duration for the consonants in non- schwa variants than in underlying clusters, or the presence of aspiration in the second consonant of non-schwa variants’ fricative-stop clusters. According to Davidson, these results are better accounted for by a process of gestural overlap than by a phonological rule of deletion.

To summarize, different phonological accounts of French schwa alternation can be found in the French phonological literature. While the dominant conception is to consider schwa alternation as the result of a phonological rule of deletion (at least for alternating initial schwa words), many alternative proposals have been made. These accounts are for the most part built on their authors’ intuitions rather than on empirical data. Yet, we believe that such data are necessary. In the present work, the issues we address are very similar to those addressed in phonological accounts. Our approach, however, is radically different. Instead of having an a priori defined phonological framework as point of departure, we start from empirical data. Once these data will be obtained, we will come back to theoretical accounts in order to examine which of them are supported by our findings.

I.3.2 Schwa’s acoustic properties

The issue of the spectral quality of schwa is closely related to that of the status of the schwa segment. It determines whether schwa should be considered as a true vowel and whether this vowel is distinct from all the other vowels of the French language. Phonological accounts of the process and representations underlying the alternation between schwa and non-schwa variants differ according to whether schwa is considered a true phoneme, with a distinct identity or not (see for instance Walker, 1993).

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The exact acoustic properties of schwa are a rather controversial issue in the literature. On the one hand, some authors assume that schwa has its own spectral quality, distinct from that of [œ] and [ø]. Rousselot (1913, cited in Malécot & Chollet, 1977) attributes to schwa an aperture between the aperture of [œ] and [ø] (see also Pleasants, 1956). In a large-scale acoustic study comparing schwa with [œ] and [ø], Fougeron, Gendrot and Bürki (2007) find that optional schwas differ from [œ] and [ø] in terms of aperture and labiality.

On the other hand, other authors attribute to schwa the spectral characteristics of an existing vowel. Malécot and Chollet (1977) conducted a computer-based identification study based on a large sample of tokens extracted from conversations. Schwa appears close to [ø]. Their data also show that schwa has less identity than any other French vowel, as shown by the tendency of the computer to confuse this vowel with other vowels.

It has also been proposed that schwa is spectrally variable, being sometimes realized as [œ] and sometimes as [ø]. According to Ayres-Bennett & Carruthers (2001), schwa is much more variable than other vowels. It is also more anterior than the neutral position assumed by the IPA alphabet and realized with a certain degree of labiality. Its spectral quality is that of [œ] or [ø]. In a similar vein, Malécot (1977) suggests that schwa’s spectral quality varies according to the segmental context and speakers’ usage. Despite this variability, it remains however closer to [ø] than to [œ] according to this author.

Finally, a few authors do not attribute to schwa precise articulatory characteristics as they do not consider schwa a real vowel. For Pernot (1929), schwa is a neutral vowel, and thus does not have a well defined articulation. Martinet (1945), on the basis of a survey documenting speakers’ representations, concludes that schwa is not a phoneme but a way to ease the articulation of adjacent consonants. As a consequence, its spectral quality does not really matter.

Several reasons may account for this lack of consensus. Firstly, it is not rare to find that a proposal relies on the author’s intuition only. Secondly, where acoustic studies have been conducted, these usually involved few speakers. The lack of appropriate statistical tests could also be mentioned. Furthermore, most (if not all) studies did not control for the differences in segmental context between the different vowels. Finally, and as underlined by Jenkins (1971), the different proposals may also reflect regional differences.

Phonological variation and lexical representation in speech production : phonetic and psycholinguistic evidence on french schwa

Thesis

Reference