The Perception of Laryngeal and Length Contrasts in Early Language Acquisition

Transcription

1 The Perception of Laryngeal and Length Contrasts in Early Language Acquisition Dissertation zur Erlangung des akademischen Grades eines Doktors der Philosophie vorgelegt von Muna Pohl an der Sektion Geisteswissenschaften Fachbereich Sprachwissenschaft Tag der mündlichen Prüfung: 12. Juli Referentin: Prof. Janet Grijzenhout 2. Referentin: Prof. Paula Fikkert

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3 Acknowledgements I never thought I would write a thesis, and even less a linguistic thesis. Yet, when I was offered the opportunity to return to university and start working in a linguistics project I had to seize the chance and soon enough I was in the middle of building up a baby lab. It would be a lie to say that it was always easy, but I never regretted my choice. The work at the linguistics department in Konstanz allowed me to meet great people and to gain experience I do not want to miss. Therefore, I want to express my gratitude to all those without whose support the present work would never have become reality and only few of which can be named in person here. Since it was her who brought me back to university and linguistics, my first thanks go to Aditi Lahiri. During the past years, of course, I got the most support from my supervisors, whom I want to express my sincere and cordial thanks. I am most grateful to Janet Grijzenhout who never lost her patience with me. I am very much indebted to her for her enlightening suggestions, the fruitful discussions and the numerous opportunities she provided me with to extend my knowledge by meeting research colleagues from all over the world. Her encouraging manner and her steadfast believe in me motivated me to carry on in several phases of severe doubt. The present work would not be what it is without the language acquisition expertise and the inspiring thoughts contributed by Paula Fikkert. I am most thankful for the time and effort she spent for my sake. By inviting me to present my work in Nijmegen, she gave me the opportunity to discuss my findings with specialists of the field, whose comments became essential for the interpretation of my data. Furthermore, I want to thank Bettina Braun. I benefited much from her helpful comments and in the short time that I have known her she has become sort of a phonetic role model to me. Of course the realisation of my thesis would have been impossible without all the children who participated in the multitudinous test sessions. I want to sincerely thank their parents for their commitment and will to come to the maze of the university from rather far away sometimes. i

4 ii I am grateful to Dirk Saleschus for lending me his memorable voice for so many times, to Astrid Kraehenmann for contributing her expertise on Swiss German as well as to Tanja Rinker for inspiring thoughts regarding the data analysis. I owe a great deal to Achim Kleinmann, Willi Nagl, Henning Reetz, Mathias Scharinger, Eva Smolka and Frank Zimmerer for their support with technical and statistical issues. Special thanks are due to Christine Ächtler-van Kan, Fatima Benabdelmoumene, Anne Gwinner, Teresa Kieseier and Martina Weller who helped me keeping the lab running and who were good company at the office. I would like to emphasise my appreciation of Anne s invaluable baby lab experience and her cordial hospitality in Montréal. The same is true for Nicole Altvater-Mackensen, who accommodated me repeatedly in Nijmegen. I would not want to have missed both her scientific as well as her amicable support. Indispensable during the last years were my friends and fellow sufferers Simon Hopp and Thomas Mayer. The countless lunch and coffee breaks I spent with them made my place of work also a place of life. At least as important as university life were all the people who reminded me of the fact that there is also a life outside. In this context I want to thank my family for keeping me company, encouraging and comforting me for being there whenever I needed them. My sister Tina is of inestimable value for me. Special thanks go to my father. Without his kindly shared project management knowledge and good advice I would never have gotten so far. I also want to thank my friends and I would like to apologise should I have been somewhat absent-minded sometimes during the last years. Thanks in particular to Melly, Niki, Uli. Last, but definitely not least, I want to thank Florian for accompanying me on this way. Thank you to all who have assisted me one way or another.

5 Contents 1 Introduction Terminological Conventions Outline Phonetic Properties The Phonetic Properties of Stops Some Terminological Remarks The Phonetics of Standard German Stops More Phonetic Correlates of Laryngeal Contrasts The Segmental and Prosodic Context Regional Variation and Speaking Rate Effects Summary The Phonetics of Swiss German Stops Effects of Context and Speaking Rate Summary and Comparison Phonological Representations Standard German Stops in Phonology Laryngeal Features Summary Swiss German Stops in Phonology Length Contrasts in Different Phonological Contexts Summary Summary and Implications for Acquisition Acquiring Phoneme Contrasts Preliminary Remarks on Phoneme Perception From Universal to Language-Specific Speech Perception The Perceptual Assimilation Model iii

6 iv CONTENTS Influencing Factors on Infant Speech Perception Summary of Infants Perception Patterns Infants Perception of Laryngeal Contrasts The Early Perception of Length Contrasts The Acquisition of a Phonological System The Resource Limitation Hypothesis Fragmentary Phonological Systems Phonological Categories in Early Language Acquisition Summary Pilot Tests with Adults An Appropriate Phonological Context Production Study with Adults Method and Stimuli Results and Discussion Perception Study with Adults Perception of a Native Contrast Perception of a Non-Native Contrast Categorisation of Stops Differing in ACT Categorisation of Stops Differing in CD General Discussion of the Pilot Tests The Switch Procedure Arguments for the Switch Procedure Experiment 1: Testing the Switch Procedure Method Results Discussion Methodological Remarks Two New Ways of Analysing the Data Additional Analyses for Experiment Re-Analysis Control Analysis Summary and Conclusions German Infants Perception of Stop Contrasts Aims and Predictions Discrimination of a Native Contrast Discrimination of a Non-Native Contrast Experiment 2: German Infants Perception of Stops

7 CONTENTS v Method Main Analysis Re-Analysis Control Analysis Overall Discussion German Infants Perception of the ACT Contrast German Infants Perception of the CD Contrast Summary German Adults Stop Contrasts Experiment 3: German Parents Perception of Stops Method Results Discussion Experiment 4: German Adults Production of Stops Method Results Discussion Discussion in View of the Infant Data The segmentation approach The heightened sensitivity approach Summary Swiss Germans Perception of Stop Contrasts Experiment 5: Swiss German Infants Perception of Stops Method Results Discussion Experiment 6: Swiss German Parents Perception of Stops Method Results Discussion Summary and Conclusions Phonetic and Phonological Fundamentals The Language Acquisition Background Stop Contrasts in Adults Speech Stop Contrasts in Language Acquisition Infant Speech Perception Research

8 vi CONTENTS Zusammenfassung 259 Appendices 265 A Test Procedures in Infant Speech Perception Research 265 A.1 The Switch Procedure A.2 The Visual Fixation Paradigm A.3 The Conditioned Head Turn Procedure A.4 The High Amplitude Sucking Procedure A.5 The Head Turn Preference Procedure A.6 The Preferential Looking Paradigm B Pilot Production Study 271 B.1 Dutch Speakers B.2 German Speakers C Additional ACT Perception Test with Adults 275 C.1 Method C.2 Results D Infant Tests: Additional Data for Habituation Phase 277 E Experiment 4: Stimuli 279 F Experiment 5: Participants and Looking Times 283 F.1 Participants F.2 Looking times G Consent Form and Questionnaire 285 Bibliography 291

9 List of Figures 2.1 Voiceless aspirated labial stop VOT continuum with three stop categories Intervocalic voiced labial stop Temporal relations in German and Swiss German stops Featural representation of stops Skeletal representation of length contrasts Swiss German syllable template Swiss German stops in a V V context Swiss German stops in a φ [ V context Swiss German stops in a C# V context Swiss German stops in a V #C context Representations of German and Swiss German stops Perception patterns Results Richardson et al. (2003) Oscillogram [@"pa] (German) Oscillogram [@"p h a] (German) Oscillogram [@"ba] (Dutch) Oscillogram [@"pa] (Dutch) Stimulus with short voicing lag (pilot perception test) Stimulus with long voicing lag (pilot perception test) ACT results (pilot perception test) Stimulus with short CD (pilot perception test) Stimulus with long CD (pilot perception test) CD results (pilot perception test) Laboratory set-up Results main analysis (Experiment 1) vii

10 viii LIST OF FIGURES 6.3 Three kinds of analyses Results re-analysis (Experiment 1) Results control analysis (Experiment 1) Stimulus Stimulus h a] Stimulus Results main analysis (Experiment 2) Results main analysis by age and contrast (Experiment 2) Results re-analysis (Experiment 2) Results re-analysis by age and contrast (Experiment 2) Test order effect for control analysis (Experiment 2) Results control analysis (Experiment 2) Results control analysis: experimental group (Experiment 2) Results control analysis: control group (Experiment 2) Results (Experiment 3) CD by PoA and by category (Experiment 4) CD by position and category (Experiment 4) ACT by PoA and by category (Experiment 4) ACT and CD in labial stops only (Experiment 4) Results main analysis (Experiment 5) Results re-analysis (Experiment 5) Default laryngeal boundary Boundary shift in voice languages Boundary maintenance in non-laryngeal languages Results (Experiment 6) C.1 Additional ACT perception results

11 List of Tables 2.1 German and Swiss German consonants German and Swiss German stops VOT in two-way stop contrasts (Lisker & Abramson 1964) German stop contrast in different positions ACT and CD in German and Swiss German word-medial stops Featural stop marking (Halle & Stevens 1971) Feature specifications for laryngeal contrasts ACT and F 2 in Pegg & Werker (1997) Infants perception of laryngeal contrasts FUL matching algorithm Different NMM effects for PoA and laryngeal contrasts ACT results pilot production study CD results pilot production study ACT and CD in pre- and posttonic contexts German, Dutch and Swiss German stops in a V "V context ACT and CD for infant stimuli Predictions: German infants Predictions: Swiss German infants Infant stimuli values Auditory stimulus conditions (Experiment 2) Three perception patterns (Experiment 2) Synthesised perception pattern (Experiment 2) Predictions and results (Experiment 2) CD results (Experiment 4) ACT in German labial stops between [@] and [a] ix

12 x LIST OF TABLES 9.1 Predictions for Swiss German infants (repetition) Tentative perception patterns (Experiment 5) B.1 Detailed production data of Dutch speakers B.2 Detailed production data of German speakers D.1 Factors in additional ANOVAs D.2 Infant tests: additional habituation data E.1 Sentences used in Experiment 4 (adult production) F.1 Participants in Experiment 5 (Swiss German infants) F.2 Looking times in Experiment 5 (main analysis) F.3 Looking times in Experiment 5 (re-analysis)

13 LIST OF ABBREVIATIONS ACT ADS CD CHTP EEG EPG ERP FUL HAS IDS ISI M MM MoA NMM NOM p.c. PAM After Closure Time Adult-Directed Speech Closure Duration Conditioned Head Turn Procedure Electroencephalography Electropalatography Event-Related Potential Featurally Underspecified Lexicon High Amplitude Sucking Infant-Directed Speech Inter-Stimulus-Interval Match Mismatch Manner of Articulation No-Mismatch Nominative personal communication Perceptual Assimilation Model xi

14 xii LIST OF ABBREVIATIONS PoA PP PRON SG SR StG SwG UG UR V VF VOT Place of Articulation Past Participle Pronoun Singular Surface Representation Standard German Swiss German Universal Grammar Underlying Representation Vowel Visual Fixation Voice Onset Time

15 Chapter 1 Introduction Sometimes, when invited to visit the Baby Speech Lab, parents react surprised, pointing out that their child is but a few months old and thus too young to be of interest for our investigations since (s)he does not speak yet. However, when young children start to speak their first words, the process of language acquisition has been going on for quite a while. Before they produce the sounds and sound sequences their mother tongue is made up of, they have already gathered a remarkable knowledge about those particular sounds and sound sequences just by listening to others linguistic utterances. Thus, a first important task young language learners have to accomplish is to pay close attention to the input they get from others and to extract information that helps figuring out how the ambient language conveys meaning. Although infants cannot directly tell us what they know about their language, there are other ways of bringing their linguistic skills to light. The present thesis focuses on these early steps of language acquisition and follows the development of speech perception in infants first and at the beginning of their second year of life. A key issue in the process of first language acquisition is to identify which sounds the native phoneme repertoire comprises and which kinds of variation are less important. Children acquiring German, for example, have to become aware that it makes a difference whether something is pronounced [ö] or [l], as in the minimal pair Reise journey leise quiet. The situation is different in Japanese, where the two sounds are not used to distinguish meaning. Thus, infants acquiring Japanese do not have to pay attention to this contrast, leading to the well-known r/l-confusion in adult native speakers of Japanese learning a second language like German or English. Besides the r/l-contrast, German infants have to learn that the meaning 1

16 2 1 Introduction remains the same irrespective of whether the first consonant in Reise is pronounced at the back of the mouth as a dorsal trill [ö] or fricative [K], or at the front with the tip of the tongue as an alveolar trill [r]. German as well as English infants have to learn that [s] differs from [f] (e.g., lustig funny luftig airy ; seal feel), but only English ones need to distinguish [s] and [T] (e.g., sink think) whereas German but not English children must know the difference between [u] and [y] (e.g., Spuren traces spüren to feel ). These are only a few examples. It is estimated that there are about 800 different speech sounds in the languages of the world around 600 consonants and 200 vowels (cf. Ladefoged 2005). However, each individual language uses only a subset of these sounds. Standard German (StG; henceforth also referred to simply as German ) and Swiss German (SwG), for instance, have phoneme inventories of approximately two dozen consonants, respectively. Regarding language acquisition, there is an ongoing debate on how children come to know which sounds are relevant in their native language. Previous studies on the early perception of consonant contrasts have shown that in their first few months, infants can distinguish more contrasts than present in their native language, implying that, from a linguistic point of view, all children start life on equal conditions, able to acquire any language as their mother tongue. Gradually they learn which sounds are contrasted systematically in the ambient language. After about 8 months, the initial universal perception skill decreases. From the age of about 10 months onwards, infants seem to pay more attention to the contrasts that are relevant in the language they are acquiring. Thus, during the first year of life, infants undergo a developmental change from having very broad perceptive capacities to a specialisation, a kind of tuning in, on the distinctive contrasts of their mother tongue. They learn to classify sounds according to the phoneme categories of the language they are exposed to. A simplified description of this so-called perceptual reorganisation suggests that in their first 6 to 8 months, infants are able to discriminate all speech sound contrasts, irrespective of their relevance in the mother tongue. Around the age of 12 months only those speech sounds are discriminated that play a role in the native phoneme inventory whereas sound contrasts without phonemic relevance are distinguished no longer (e.g., Werker & Tees 1984). Although the principal claim that perception changes from a universal to a language-specific one seems to be correct, it has become apparent that infants perception of phonetic contrasts is more complex than the reduction process described above. First of all, the assumptions are based on the examination of consonant contrasts. For vowels, a similar development could be observed, yet sometimes with a different timeline, suggesting even

17 3 faster reorganisation to language-specific perception already at 6 months of age (e.g., Kuhl et al. 1992; Polka & Werker 1994). Secondly, it has been shown that not all non-native contrasts are indistinguishable after the first year of life. Some contrasts are reliably discriminated by children older than 12 months and by adults, although the sounds in question are not contrasted phonemically in their mother tongue (e.g., Best et al. 1988). Furthermore, although infants in their first months of life are ascribed extraordinary perception skills exceeding adults perceptual abilities, it was demonstrated that not all contrasts are discriminated equally well at the beginning and that the discriminative capacity may be improved with a certain amount of linguistic experience (e.g., Polka et al. 2001; Narayan et al. 2010). In addition, the relation between the phonetic properties of a given non-native contrast and the respective native phoneme categories seems to affect the discriminability of that contrast (e.g., Best et al. 2001; Best & McRoberts 2003). Thus, infants perceptual development during the first year of life should not be described as a simple reduction from all to native contrasts only. Rather, it requires a differentiated inspection that takes the phonetic and phonological properties of the involved languages into account. As a point of departure, discriminability of a contrast may vary on a scale between clear distinctiveness on the one hand, resulting in early very robust discrimination, and minimal distinctiveness on the other hand, making the contrast hard to perceive. There are also several options how the perception of a contrast may evolve in the course of time. Discriminability may be facilitated, leading to an improved distinction at the end of the first year. Alternatively, it can be reduced, so that a contrast is completely ignored around 12 months. Finally, discriminability may not change at all, maintaining the initial level of discriminability also later in life. Although some findings seem to be valid cross-linguistically, the way in which a particular contrast develops cannot be described universally but has to be determined language-specifically. The present work contributes to this debate of how infants come to know their required phoneme repertoire by examining the early perception of sound contrasts in German and Swiss German two languages which are closely related yet typologically different with regard to their phoneme inventories. The focus is put on infants perception of stop contrasts. Both the German and the Swiss German consonant inventories comprise two series of stops, orthographically represented as <b, d, g> on the one hand and <p,t,k> on the other hand. However, the contrasts differ in their phonetic implementation as well as in their phonological representation. The German stop system exhibits a contrast between voiceless unaspirated stops

18 4 1 Introduction and voiceless aspirated stops (e.g., Jessen 1998). The aperture between the vocal folds and their level of tension are distinctive in the realisation of the contrast, which therefore is referred to as a laryngeal contrast. It is assumed to be phonologically represented by means of distinctive features. In Swiss German, laryngeal configurations are not applied contrastively. Instead, the duration of oral obstruction during stop production is distinctive. Therefore, the Swiss German distinction is called a length contrast, in which short stops, so-called singletons are opposed to long stops, so-called geminates. The phonological representation of the contrast is suggested to take place on a suprasegmental level, without reference to distinctive features. While laryngeal contrasts are very common in the languages of the world, the Swiss German stop system is rather unique in the West Germanic languages and rare also in a broader context, as Lahiri & Kraehenmann (2004:18f.) note: None of the standard dialects of the modern West Germanic languages maintain an underlying contrast in length for both consonants and vowels. In Dutch, English, and German, vowel quantity distinction is maintained, but not consonant length. In dialects of Swiss German like Thurgovian, however, both consonant and vowel quantity coexist [... ]. [T]he medial [consonant] contrast is a fairly robust one in many languages. What is different about Thurgovian is, of course, the fact that it has a geminate/singleton contrast also in both initial and final position. With respect to the acquisition of stops, German and Swiss German children thus have a different task to accomplish. German children have to learn that laryngeal properties in the speech signal matter to make a contrast between two classes of stops, whereas Swiss German children have to learn to pay attention to differences in the length of two classes of stops instead. There are quite some studies on infants perception of laryngeal contrasts, though mostly examining infants from an English language background (e.g., Eimas et al. 1971; Aslin et al. 1981; Rivera-Gaxiola et al. 2005; Conboy et al. 2008). There is no evidence as yet, demonstrating that German infants perception of stop contrasts develops along the same lines. Regarding infants perception of duration contrasts, there are some insights, for example, into infants acquiring English (e.g., Cohen et al. 1992) or Finnish (e.g., Richardson et al. 2003). Yet, overall, studies on the early perception of length contrasts in stops both as native and as non-native contrasts are more scarce than the literature on laryngeal contrasts. In particular, no studies are known that examine infants perception of Swiss German stop contrasts. The present thesis aims to fill these gaps. Firstly, German infants perception of both a native laryngeal stop contrast and a non-native length contrast will be

19 1.1 Terminological Conventions 5 examined. Secondly, data on Swiss German infants perception of the same contrasts will provide some first insights into the perception of (a) a nonnative laryngeal contrast by infants whose mother tongue lacks a laryngeal contrast and (b) a native singleton/geminate contrast. Accordingly, the present work allows to determine the developmental paths for the German laryngeal contrast and the Swiss German length contrast, both from the perspective of native contrast acquisition as well as concerning non-native contrast perception. By comparing the German to the Swiss German stop contrast, the present work does not only examine two different consonant contrasts, but also two different types of contrast. The laryngeal and the length contrast differ both in their phonetic properties as well as in the way in which they are assumed to be represented phonologically. Therefore, it may be expected that the acquisition of laryngeal contrasts on the one hand and length contrasts on the other hand show different developmental paths. Although the focus on two languages only is too narrow to draw final conclusions, the insights gathered here provide an initial basis for future research into typological regularities in infants perception of cues in the speech signal other than place and manner of articulation. 1.1 Terminological Conventions In order to avoid confusion, some clarifying remarks concerning the terminology shall be made. In the present work, the term phonetic is intended to refer to concrete measurable, acoustic or articulatory aspects of the speech signal. Phonemic, in contrast, refers to the abstract phonological concept of the phoneme, the smallest distinctive segmental unit in a language. Stop contrasts in German and Swiss German are at the centre of the present thesis. As indicated above, both languages display a two-way contrast between <b, d, g> and <p, t, k> in their respective stop system. A source of repeated confusion lies in the labels voiced and voiceless which are often applied to describe such two-way contrasts. From a phonetic point of view neither German nor Swiss German opposes voiced to voiceless stops. Chapter 2 reveals that German has a contrast between voiceless unaspirated and voiceless aspirated stops whereas Swiss German distinguishes singletons and geminates. A contrast between phonetically voiced and voiceless stops is found, for example, in French or in Dutch. Thus, the terms voiced and voiceless might be used as abstract phonological labels which do not necessarily refer to the phonetic correlates of the given phones. In order to avoid confusion about whether the terms voiced and voiceless refer to the pho-

20 6 1 Introduction netic reality or rather to abstract phonological conceptions, the more neutral terms lax and tense will be used when speaking about the two stop series. In other words, lax is used as a phonetically non-specific term to refer to (a) the voiced members of a contrast in languages that oppose phonetically voiced to phonetically voiceless stops (e.g., French), (b) the voiceless unaspirated members of a contrast in languages that oppose voiceless unaspirated to voiceless aspirated stops (e.g., German), and (c) the short stops in languages that oppose singletons to geminates (e.g., Swiss German). Tense is used to refer to the respective contrasting members, that is (a) to phonetically voiceless stops in French, (b) to voiceless aspirated stops in German, and (c) to long stops in Swiss German. In the present work, the terms voiceless, voiced and voiceless aspirated always refer to the phonetic quality of the sounds. Additionally, in order to emphasise the phonetic aspect for voiced stops, they are sometimes referred to as prevoiced. The phonetic details pertaining to these labels will be discussed in chapter 2. In recognition of the phonetic implementation of the stop contrast in German as an opposition between voiceless unaspirated and voiceless aspirated stops, underlying /b, d, g/ are transcribed as [p, t, k] in the surface representations, and underlying /p, t, k/ are represented as [p h,t h,k h ] on the surface. Swiss German lax stops are transcribed as /p, t, k/ and [p, t, k] and the tense series is represented as /p:, t:, k:/ and [p:, t:, k:]. When speaking about stops, the label length contrast is used to refer to systematic differences in closure duration as in the Swiss German singleton/geminate contrast. Although the German contrast is also based on a temporal measure, namely the duration of aspiration, it is not referred to as length contrast but as laryngeal contrast, since properties of phonation constitute the basis of the contrast. Some remarks are due with regard to children and the topic of first language acquisition research. When speaking of German/Swiss German/English/... infants, this denotation is not supposed to express infants nationality or the fact that they are already competent speakers of the respective language. Rather, it is meant to refer to their language background and is used as a shortcut for infants acquiring German/Swiss German/English/... as their first language. Mostly, infants age is explicitly indicated in months. Yet, sometimes an indication like x; y may occur. In this case, x represents years and y refers to months. Finally, various methods used in infant speech perception research are mentioned in the following chapters. In order to stick to the central theme and avoid methodological digressions, these procedures are explained at most briefly in the main text. A detailed description of the methods is provided in appendix A.

21 1.2 Outline Outline The first part of the present thesis, comprising chapters 2, 3 and 4, provides the theoretical background on which the empirical research presented in the second part is based. Chapters 5 to 9 present new data on infants and adults perception (and partially also production) of laryngeal and length contrasts as present in German and Swiss German respectively. The structure of the thesis is as follows. After some general remarks on the two languages under investigation, chapter 2 addresses the phonetic properties of stops at first in a rather general way and subsequently with respect to the characteristics specific for German and Swiss German stops. It will become clear that the two languages make use of different types of contrast in order to distinguish two stop series. A review of the literature shows that a parameter called after closure time is the most important phonetic correlate in the German tense/lax opposition which differentiates voiceless unaspirated and voiceless aspirated stops. Following the studies by Kraehenmann (2001, 2003), Swiss German is shown to employ a singleton/geminate contrast with closure duration as the distinctive parameter. Furthermore, the inspection of the phonetic properties of German and Swiss German stops reveals a slightly asymmetric pattern regarding the application of the parameter that is considered to be non-native in the respective language. In Swiss German, tense and lax stops are more or less identical in their laryngeal configuration: Both stop series are voiceless unaspirated. In German, tense and lax stops display small differences in their closure duration, with on average slightly longer closures for the tense series. Typological differences between the laryngeal and the length contrast are found not only on the phonetic level but also regarding phonology. Chapter 3 provides some phonological fundamentals regarding the respective abstract representations of German and Swiss German stops. Laryngeal contrasts are assumed to be represented by distinctive features whereas length contrasts are specified suprasegmentally by reference to timing structure. Considering the tense/lax opposition in German it becomes apparent that there is no unified standard which particular feature specification should be used to represent laryngeal contrasts. A sketch of an ongoing debate in the literature on laryngeal specifications mentions different alternatives suggested to represent laryngeal contrasts. In the context of this discussion the typological labels voice language and aspiration language are introduced in order to distinguish between languages with different phonetic implementations of two-way laryngeal contrasts. Considering Swiss German, chapter 3 briefly introduces Kraehenmann s (2001, 2003) model of length contrast specifica-

22 8 1 Introduction tion. It is based on the assumption that short stops are linked to one timing unit whereas geminates occupy two timing units on a syllabic tier, with differential consequences for syllable structure. Yet, since the present thesis is concerned mainly with phonetic aspects of stop contrasts in German and Swiss German, chapter 3 is not intended to provide an exhaustive account of phonological representations but rather some basic background information. Chapter 4 reports on the findings published in previous studies on infant speech perception. First of all, the pattern of perceptual reorganisation regarding infants discriminative capacities of speech sound contrasts in their first year of life is discussed at length. It is shown that the development from universal to language-specific perception may take different paths for different contrasts. A brief summary of the so-called perceptual assimilation model (e.g., Best et al. 2001; Best & McRoberts 2003) provides a theoretical basis on which predictions for infants and adults perception of speech contrasts can be formulated. In the literature review on infants contrast discrimination skills, special emphasis is put on studies focusing on the early perception of laryngeal and length contrasts. It will become obvious that the findings of different studies are consistent neither for laryngeal nor for length contrasts. Yet the data on infants perception of laryngeal contrasts converge to suggest that the tense/lax opposition as it is implemented in German is rather robustly discriminated in the first months of life, implying that the contrast just has to be maintained if required by the mother tongue. The distinction between voiced and voiceless stops, on the other hand, seems to be more difficult for very young infants, suggesting that some linguistic experience may be necessary to achieve adult-like mastery. While there is ample literature on laryngeal contrasts in first language acquisition, studies on the early perception of consonantal length contrasts are more rare and they do not permit to ultimately determine whether the length contrast in stops is easily discriminable in the first months of life or whether successful discrimination is acquired only with a certain amount of linguistic experience. In chapter 4, the main focus will be on the developments observable in the first year of life. Nonetheless, some further aspects such as the beginnings of the acquisition of a phonological system in the second year of life will also be addressed. Specifically, the finding that 14-month-olds sometimes have difficulties in distinguishing a native stop contrast (e.g., Stager & Werker 1997) entailed an extensive discourse on how early phonological representations may look like. In the context of this debate, Pierrehumbert s (2001, 2003) exemplar-theoretic account of language acquisition is introduced, a model that is taken up again later in the interpretation of the data collected for the present thesis.

23 1.2 Outline 9 The presentation of new empirical data begins in chapter 5. Two pilot studies examining adults production and perception of laryngeal and length contrasts provide an essential basis for the experiments on infants perception of stop contrasts. The production data of German adults and a detailed comparison with the findings reported by Kraehenmann (2001, 2003) for Swiss German focus again on the phonetic details of stops in the two languages, precisely in the context that becomes relevant later in the infant tests. A study of adults categorisation skills regarding stops differing either in after closure time (the relevant parameter in German) or in closure duration (the distinctive cue in Swiss German) reveals the location of the phoneme boundaries separating the tense category from the lax category in the two languages, respectively. Moreover, the perception study provides insights into adults perception of the two types of contrast as non-native contrasts. It is demonstrated that German adults have difficulties in categorically distinguishing short and long stops. The German laryngeal contrast is considered to be a non-native contrast for both Swiss German and Dutch adults. Nonetheless, their respective categorisation behaviours differ. While Swiss Germans exhibit reliable categorisation of the non-native laryngeal contrasts, Dutch listeners fail to assign stops differing in after closure time to their native stop categories. A first interpretation suggests that typological differences between the two languages may account for the discrepant categorisation abilities. The findings of the following chapters seem to support this assumption so that the hypothesis is explicated in more detail in chapter 9. Before addressing infants perception of laryngeal and length contrasts, chapter 6 reports on a precursory experiment with 6- to 8-month-old infants acquiring German. In order to test the Switch Procedure at the Baby Speech Lab at the University of Konstanz, the infants discrimination ability of a contrast between two phonetically highly dissimilar non-words was assessed. In addition to the analysis commonly applied to data collected with this method, two alternative ways of looking at the data are introduced. Since they can be shown to provide a more sensitive measure for the evaluation of infants discriminative capacities, both additional analyses are included in the following infant experiments. Chapter 7 can be said to represent the centrepiece of the present thesis since it addresses the principal question about infants perception of stop contrasts as they occur in German and in Swiss German. First of all, the point of departure and the ensuing expectations are described in detail and with regard to both German and Swiss German infants. Next, an experiment with three age groups of German infants reveals the development of

24 10 1 Introduction the discriminability of a laryngeal and a length contrast in labial stops between 6 and 16 months of age. The combined results of the three kinds of analyses suggest that German infants reliably discriminate the native laryngeal contrast at 6 to 8 and at 10 to 12 months of age but they seem to lose this skill between 14 and 16 months. The non-native length contrast is discriminated only by the two older age groups but not by the youngest infants. The latter aspect is considered as an indicator that consonantal length contrasts are not universally discriminable in the first months of life but require some linguistic experience to be reliably discriminated. Based on Pierrehumbert s (2001, 2003) exemplar-theoretic account of language acquisition, 14- to 16-month-olds insensitivity to the native contrast is accounted for by reference to a temporary phase of confusion at the beginning of the second year of life, which is caused by an increasingly variable linguistic input. Two suggestions are made with respect to the finding that German infants apparently learn to discriminate the (presumed) non-native length contrast. Either infants are more sensitive to length contrasts as cues to categorical distinctions than adults or they use the fine phonetic differences in order to detect word boundaries. The partially unexpected findings presented in chapter 7 led to two additional experiments with German adults, which are presented in chapter 8. The categorisation study that was already conducted as a pilot test, is repeated with the infants parents. The previous findings are replicated, demonstrating that German parents display categorical perception for laryngeal contrasts but not for length contrasts. Moreover, the values chosen for the infant stimuli are appropriate representatives of the two German stop categories in the case of the laryngeal contrast whereas they fall into a zone of ambiguity in the case of the length contrast. A second experiment with German adults provides additional production data on stops in word-initial and word-medial position. Since the analysis of adults productions yields significant effects both with regard to the position in which the stops occur as well as concerning laryngeal categories, the results do not allow to ultimately determine whether the infants used the length contrast as a cue for segmentation or for phoneme distinction. Referring, among other things, to the stronger category effect, the phoneme distinction account is favoured. Chapter 9 presents the findings on Swiss German infants and their parents perception of laryngeal and length contrasts. The experiment with German infants reported in chapter 7 is repeated with Swiss German infants. However, since fewer observations are available, it provides only preliminary insights into Swiss German infants perception of the two contrasts in question. The data seem to support the assumption that the Swiss German

25 1.2 Outline 11 singleton/geminate stop contrast is not discriminable from birth but has to be acquired with linguistic experience. Swiss German infants in the present experiment seem to become sensitive to the contrast not before 10 months of age. Also, an insensitivity to the native contrast at 14 to 16 months could be observed, providing more support for the assumption that native phoneme categories may not be as stable as suggested in previous work by others. Moreover, Swiss German infants of all three age groups seem to succeed in discriminating the non-native laryngeal contrast. Together with the results of the adult perception test this finding is interpreted with reference to the typological properties of the language. Since laryngeal configurations are not employed contrastively in Swiss German, an assumed default boundary corresponding roughly to the boundary separating tense and lax stops in German is maintained despite its irrelevance for the native phoneme inventory. In analogy to the experiments with Germans, chapter 9 reports on Swiss German parents categorisation skills concerning laryngeal and length contrasts. As with the Germans, the Swiss German parent data replicate the findings of the pilot perception studies, providing more support for the appropriateness of the values chosen for the infant stimuli. Finally, chapter 10 concludes the thesis with a summary of the main findings and ensuing conclusions. Furthermore, the chapter addresses some open questions, and future prospects for further research are mentioned.

26 12 1 Introduction

27 Chapter 2 Phonetic Properties of Standard German and Swiss German Stops Standard German and Swiss German are closely related languages. Both belong to the West Germanic language family. Yet, in spite of numerous similarities there are striking differences which clearly distinguish Standard German from Swiss German. Differences are found on the lexical and morphological level, as example (1) demonstrates. (1) Standard German Swiss German Gloss Pfand Depot deposit umziehen zügeln to move house Fahrrad Velo bicycle Eis Glacé ice cream Torwart Goalie goal keeper Unterbrechung Unterbruch interruption parken parkieren to park More differences are found in the syntactic structures of the respective languages, as exemplified in (2). 13

28 14 2 Phonetic Properties (2) a. StG: Für das Teil musste ich in der ganzen Stadt herumrennen. SwG: Für das Teili hani müesse i de ganze Stadt umecheibe. 1 Gloss: For this thing I had to run around in the whole city. b. StG:..., dass er eine Arie hat singen wollen. SwG:..., dass er en Arie het wele singe. 2 Gloss:... that he wanted to sing an aria. Grammatical distinctions are also ascertained with regard to tense formation. In contrast to Standard German, Swiss German lacks an imperfect (e.g., StG: ich ging I went ) and subsequently also a pluperfect (e.g., StG: ich war gegangen I had gone ). Instead, Swiss German has a tense which is not found in Standard German and which Siebenhaar & Wyler (1997:37) describe as a kind of hyper-perfect ( eine Art Überperfekt ): ich bi ggange gsi (pron-1sg-nom; be-1sg; go-pp; be-pp). Furthermore, the two languages differ substantially in their phonetic and phonological properties. There are conspicuous pronunciation differences which go so far that speakers of Standard German often have difficulties in understanding Swiss German. These very obvious differences and also more subtle distinctions are not only found on the surface but are also reflected in different underlying phonological systems. The respective consonant inventories for Standard German and Swiss German in table 2.1 (assembled from different sources discussed below) reveal some of the differences between the two languages. A few remarks are due regarding the Standard German consonant inventory. The underlying phoneme /x/ may surface as allophonic variants [ç] and [x] and possibly the even further back [X] whose distribution can be deduced from context (cf. Kohler 1990b). 3 Allophonic surface forms are also observed for the phoneme /ö/, which occurs in free variation with the alveolar trill [r] and the uvular fricative [K]. Moreover, postvocalic /ö/ in final position usually surfaces as the central vowel [5]. The glottal stop [P] does not have phonemic function in Standard German phonology and it occurs only in surface representations. 4 [Z] and [ > dz] are not very common. They 1 (03/10). 2 (03/10). 3 It might also be assumed that palatal /ç/ is the most appropriate symbol for the underlying representation of the German dorsal fricative (e.g., Hall 2000). Kohler (1990b) provides a short discussion on this issue. 4 The glottal stop [P] differs from the other stops in the fact that the obstruction of air does not take place in the oral tract, but rather in the larynx by pressing the vocal cords together so that the air from the lungs cannot escape through the glottis. In foot-initial position, the glottal stop is inserted as an onset in syllables underlyingly starting with a

29 15 Bilabial Labiodental Alveolar Postalveolar Palatal Velar Uvular Stop pb td k g p: p t: t k: k Nasal m n N m: m n: n N: Trill ö ö Fricative f v s z SZ x h f: f s: s S: S x: x h Approximant j j Lateral l approximant l: l > > > > Affricate pf ts ts dz > > > > pf ts ts kx Glottal Table 2.1: Consonantal phoneme inventory of Standard German (upper lines) and Swiss German (lower lines). were introduced to the system through language contact and are restricted to loanwords such as Garage [ka"ka:z@] ( garage ) and Dschungel [" > dzunl] ( jungle ). 5 Regarding the Swiss German phoneme inventory, a system has been adopted here that largely follows Kraehenmann s (2003:41) account of the Thurgovian dialect of Swiss German. 6 Her system deviates from the phoneme vowel: For instance, /"a > pf@l/ becomes ["Pa > pfl " ]. A distinctive function is given only in the differentiation of affirmative and negating utterances (cf. Ladefoged 2006:60f.). 5 The present system lists affricates as proper phonemes, an approach that is also followed by Hakkarainen (1995) and Hall (2000), for example. Other authors, like Kohler (1990a, 1995), stick to the IPA-chart suggested by the International Phonetic Association and exclude affricates from their phoneme tables of Standard German, inducing an interpretation of affricates as a synthesis of an oral stop released into a (mostly homorganic) fricative. The unclear status of affricates is also discussed in Wiese (2000:13f.). Furthermore, there is an ongoing debate on the phoneme status of some fricatives, nasals and liquids, which will be ignored here. 6 Kraehenmann (2001, 2003) represents length by using the same symbol twice (e.g., a long labial stop is represented as [pp]). In the present thesis, the IPA length symbol : is preferred to express both consonant and vowel length.