Functional Phonology Functional Phonology Formalizing the interactions between articulatory and perceptual drives Academisch proefschrift ter verkrijging van de graad van doctor aan de Universiteit van Amsterdam, op gezag van de Rector Magnificus prof. dr. J.J.M. Franse ten overstaan van een door het college voor promoties ingestelde commissie in het openbaar te verdedigen in de Aula der Universiteit op maandag 14 september 1998 te 13.00 uur door Paulus Petrus Gerardus Boersma geboren te Sint Nicolaasga FaculteitderGeesteswetenschappen UniversiteitvanAmsterdam Promotor: prof.dr.ir.L.C.W.Pols Overigecommissieleden: prof.dr.C.H.M.Gussenhoven dr.V.J.vanHeuven prof.dr.G.E.Booij prof.dr.A.M.Bolkestein dr.N.S.H.Smith Uitgavevan HollandAcademicGraphics phone:+31704480203 P.O.Box53292 fax:+31704480177 2505AG TheHague e-mail:[email protected] TheNetherlands http:www.hag.nl ISBN90-5569-54-6 NUGI941 Copyright©1998byPaulBoersma.Allerechtenvoorbehouden. PrintedintheNetherlands. Contents INTRODUCTION ...........................................................................................................................................1 0.1 Articulatory and perceptual representations ............................................................................................1 0.2 Functional principles and constraints of articulation and perception ......................................................2 0.2.1 Functional principles of speech production ................................................................................2 0.2.2 Functional principle of the communication channel ...................................................................2 0.2.3 Functional principles of speech perception .................................................................................2 0.2.4 The functional hypothesis for phonology ...................................................................................2 0.2.5 Conflicts between functional principles ......................................................................................3 0.2.6 Formalizing functional principles ...............................................................................................4 0.2.7 Interactions between the constraints ...........................................................................................4 0.3 Production and perception grammars ......................................................................................................5 PART I: REPRESENTATIONS ..................................................................................................................7 1. REPRESENTATIONS AND FEATURES .................................................................................................9 1.1 Articulatory and perceptual representations of an utterance ...................................................................9 1.2 Articulatory, perceptual, and hybrid features ........................................................................................10 1.2.1 Articulation versus perception in speech production ................................................................10 1.2.2 The two targets of speech production: two levels of specification ...........................................13 1.2.3 Perceptual specifications ...........................................................................................................14 1.2.4 Articulatory specifications ........................................................................................................15 1.2.5 Perceptual versus articulatory features ......................................................................................16 1.2.6 The speech-neutral position and privative features ..................................................................22 1.2.7 Feature geometries ....................................................................................................................22 1.2.8 Conclusion ................................................................................................................................23 1.3 Hybrid, articulatory, and perceptual representations .............................................................................24 1.3.1 Hybrid representations ..............................................................................................................24 1.3.2 Articulatory phonology .............................................................................................................26 1.3.3 The specification – articulation – perception triad ....................................................................27 1.4 Formalization of functional principles ..................................................................................................30 2. ARTICULATION MODEL ......................................................................................................................31 2.1 Requirements .........................................................................................................................................31 2.1.1 Specification of the input: muscle activities or tasks? ..............................................................32 2.1.2 Controlling the muscles ............................................................................................................32 2.1.3 Smooth trajectories ...................................................................................................................33 2.1.4 Aerodynamic-myoelastic interaction ........................................................................................33 2.1.5 Timing .......................................................................................................................................34 2.1.6 Generating acoustic output ........................................................................................................34 2.2 Overview of the articulation model .......................................................................................................36 2.3 The springs and the masses ....................................................................................................................38 2.3.1 Equation of motion ....................................................................................................................38 2.3.2 The tension force .......................................................................................................................38 2.3.3 The collision force ....................................................................................................................40 2.3.4 The coupling force ....................................................................................................................42 2.3.5 The damping force ....................................................................................................................42 ii CONTENTS 2.3.6 The air pressure force ................................................................................................................43 2.3.7 Parallel subdivision ...................................................................................................................43 2.3.8 The z direction ..........................................................................................................................43 2.4 From muscles to tract shape ..................................................................................................................43 2.5 Speaker properties .................................................................................................................................44 2.5.1 Three sizes of speakers ..............................................................................................................45 2.5.2 Default values ...........................................................................................................................45 2.6 Sublaryngeal system ..............................................................................................................................46 2.7 Larynx ....................................................................................................................................................48 2.7.1 Conus elasticus ..........................................................................................................................48 2.7.2 Intermembranous glottis ...........................................................................................................48 2.7.3 Intercartilagenous glottis ...........................................................................................................51 2.8 Nasal cavities .........................................................................................................................................51 2.9 Pharyngeal and oral cavities ..................................................................................................................52 2.9.1 Upper part of the larynx ............................................................................................................52 2.9.2 Jaw and tongue body .................................................................................................................53 2.9.3 Tongue root ...............................................................................................................................54 2.9.4 Velum and palate ......................................................................................................................56 2.9.5 Tongue tip .................................................................................................................................56 2.9.6 Teeth ..........................................................................................................................................57 2.9.7 Lips ............................................................................................................................................57 2.10 Meshing of the vocal tract ...................................................................................................................57 2.10.1 Mesh points on the outer contour ............................................................................................58 2.10.2 The midlines of the tube sections ............................................................................................58 2.10.3 The lengths of the mesh lines ..................................................................................................60 2.10.4 Equilibrium widths of pharyngeal and oral tube sections .......................................................60 2.10.5 Equilibrium lengths of pharyngeal and oral tube sections ......................................................61 2.11 Other oral and pharyngeal properties ..................................................................................................62 2.12 Time .....................................................................................................................................................62 2.13 Conclusion ...........................................................................................................................................63 3. ACOUSTICAL SIMULATION ................................................................................................................65 3.1 The equation of continuity of mass flow ...............................................................................................65 3.1.1 The integral equation of continuity ...........................................................................................65 3.1.2 Pumping and sucking ................................................................................................................66 3.1.3 Others’ choices for the continuity equation ..............................................................................67 3.2 The equation of motion ..........................................................................................................................68 3.2.1 Pressure gradient .......................................................................................................................68 3.2.2 Bernoulli effect .........................................................................................................................69 3.2.3 Friction ......................................................................................................................................70 3.2.4 Complete equation of motion ....................................................................................................73 3.2.5 Others’ choices for the equation of motion ...............................................................................73 3.3 The equation of state ..............................................................................................................................73 3.4 Turbulence .............................................................................................................................................74 3.4.1 Energy loss ................................................................................................................................74 3.4.2 Turbulence noise .......................................................................................................................75 3.5 Boundary conditions ..............................................................................................................................76 3.5.1 At a closed boundary ................................................................................................................76 3.5.2 At a boundary open to the atmosphere ......................................................................................77 3.5.3 At a boundary between two tube sections .................................................................................77 3.5.4 At a three-way boundary ...........................................................................................................78 3.6 Simplifying the aerodynamic equations ................................................................................................79 3.6.1 The aerodynamic equations in terms of continuous quantities .................................................79 3.6.2 Eliminating the equation of state ..............................................................................................79 3.6.3 A paradoxical factor of one half ................................................................................................80 3.7 Acoustic output ......................................................................................................................................80 CONTENTS iii 3.8 Digital simulation ..................................................................................................................................81 3.9 The dissipative part of the equations .....................................................................................................82 3.9.1 The exponential method ............................................................................................................82 3.9.2 The first-order explicit method .................................................................................................83 3.9.3 The first-order implicit method .................................................................................................83 3.9.4 The second-order method ..........................................................................................................84 3.9.5 Which method should we use? ..................................................................................................85 3.10 The harmonic part of the myo-elastic equations ..................................................................................85 3.10.1 The “explicit” method .............................................................................................................86 3.10.2 The “exact” method ................................................................................................................87 3.10.3 The “implicit” method ............................................................................................................87 3.10.4 The “second-order” method ....................................................................................................88 3.10.5 The amplitude of the periodic motion .....................................................................................88 3.10.6 Which method should we use? ................................................................................................89 3.11 The hyperbolic part of the aerodynamic equations ..............................................................................89 3.11.1 The Lax-Wendroff method .....................................................................................................90 3.11.2 Stability, numerical damping, and frequency warping ...........................................................91 3.11.3 Four extensions to the Lax-Wendroff method ........................................................................94 3.11.4 Stability, frequency warping, and numerical damping ...........................................................97 3.11.5 Accuracy .................................................................................................................................97 3.12 The algorithm ......................................................................................................................................98 3.13 Conclusion .........................................................................................................................................102 4. PERCEPTION MODELS ........................................................................................................................103 4.1 Pitch .....................................................................................................................................................103 4.2 Perceptual spectrum .............................................................................................................................103 4.3 Intensity ...............................................................................................................................................109 4.4 Contrast and confusion ........................................................................................................................110 4.4.1 Discrete measures ...................................................................................................................110 4.4.2 Combining various perceptual dimensions to a global contrast measure ...............................110 4.4.3 Perceptual salience versus dissimilarity ..................................................................................112 4.5 Conclusion .............................................................................................................................................112 5. TEST OF THE ARTICULATION MODEL ...........................................................................................113 5.1 Silence ..................................................................................................................................................113 5.2 Sigh ......................................................................................................................................................113 5.3 Balloon ................................................................................................................................................116 5.4 The onset of phonation ........................................................................................................................118 5.5 During phonation .................................................................................................................................118 5.5.1 The motion of the vocal folds during phonation .....................................................................118 5.5.2 Air velocity in the glottis during phonation ............................................................................120 5.5.3 Air pressure in and around the glottis during phonation .........................................................120 5.6 Sustained phonation .............................................................................................................................122 5.7 Varying lung pressure ..........................................................................................................................124 5.8 Phonetogram ........................................................................................................................................127 5.9 Voicing in obstruents ...........................................................................................................................128 5.10 Voicing contrast using glottal width: aspiration ................................................................................130 5.11 Voicing contrast using tract-wall tension: fortis - lenis .....................................................................133 5.12 Place-dependent maintenance of voicing ..........................................................................................134 5.13 Voiceless by glottal constriction: ejectives ........................................................................................136 5.13.1 The production of ejectives ...................................................................................................136 5.13.2 Simulation of ejectives ..........................................................................................................137 5.14 Trills ..................................................................................................................................................138 5.15 Clicks .................................................................................................................................................138 5.16 Conclusion .........................................................................................................................................140 iv CONTENTS PART II: CONSTRAINTS .......................................................................................................................141 6. FUNCTIONAL OPTIMALITY THEORY .............................................................................................143 6.1 Grammar model ...................................................................................................................................143 6.2 Constraint-ranking grammars and functionalism ................................................................................144 6.2.1 Explanation versus description ...............................................................................................144 6.2.2 Constraint-ranking grammars .................................................................................................145 6.3 The production grammar .....................................................................................................................146 6.4 The perception grammar ......................................................................................................................147 6.5 Conclusion ...........................................................................................................................................148 7. ARTICULATORY CONSTRAINTS ......................................................................................................149 7.1 Energy ..................................................................................................................................................149 7.2 Number of gestures ..............................................................................................................................151 7.3 Synchronization ...................................................................................................................................154 7.4 Precision ..............................................................................................................................................155 7.5 Coordination ........................................................................................................................................156 7.6 Global or local rankings of effort? ......................................................................................................158 7.7 Ranking by specificity .........................................................................................................................159 7.8 A restriction on functional rankings of articulatory constraints ..........................................................159 7.9 A comprehensive gestural constraint and additive ranking .................................................................159 7.10 Conclusion .........................................................................................................................................160 8. PERCEPTUAL CATEGORIZATION AND THE EMERGENCE OF FINITENESS ..........................161 8.1 Feature values are not innate ...............................................................................................................161 8.2 Constraints in speech production .........................................................................................................162 8.3 Functional constraints in speech perception: categorization ...............................................................163 8.4 Categorization along a single perceptual dimension ...........................................................................165 8.5 Special case: weak categories ..............................................................................................................168 8.6 Special case: unparsed features ...........................................................................................................169 8.7 Dependence on environment ...............................................................................................................170 8.8 Merger ..................................................................................................................................................170 8.9 Conclusion ...........................................................................................................................................171 9. PERCEPTUAL CONTRAST AND FAITHFULNESS ..........................................................................173 9.1 How to implement minimization of confusion ....................................................................................173 9.1.1 Global optimization ................................................................................................................173 9.1.2 The local-ranking principle .....................................................................................................174 9.1.3 Local implementation: faithfulness .........................................................................................174 9.1.4 Faithfulness in phonetic implementation ................................................................................175 9.2 Faithfulness in phonology ....................................................................................................................176 9.3 The emergence of equally spaced categories ......................................................................................179 9.4 Extreme feature values ........................................................................................................................180 9.5 Category strength: ranking *REPLACE by markedness ......................................................................180 9.6 Information ..........................................................................................................................................184 9.7 Binary features .....................................................................................................................................185 9.8 Correspondence strategy for binary features .......................................................................................186 9.9 Privative features .................................................................................................................................189 9.10 Ranking by specificity .......................................................................................................................192 9.11 Simultaneity constraints ....................................................................................................................193 9.12 Precedence constraints .......................................................................................................................194 9.13 Alignment constraints ........................................................................................................................196 9.14 Global or local ranking of faithfulness constraints? ..........................................................................201 9.15 Conclusion .........................................................................................................................................201 CONTENTS v 10. ACOUSTICAL FAITHFULNESS ........................................................................................................203 10.1 Interaction between articulation and perception ................................................................................203 10.1.1 Inherent conflicts ...................................................................................................................205 10.1.2 No interaction constraints .....................................................................................................206 10.2 Constraints for vowel height ..............................................................................................................206 10.2.1 Specification: perceptual constraints .....................................................................................206 10.2.2 Articulatory constraints .........................................................................................................207 10.3 Articulation-to-perception transformation .........................................................................................208 10.4 Interaction of articulatory and perceptual constraints .......................................................................208 10.5 Shifting the working point .................................................................................................................210 10.5.1 Dependence on stress ............................................................................................................210 10.5.2 Dependence on surrounding consonants ...............................................................................212 10.5.3 Dependence on duration ........................................................................................................212 10.5.4 Dependence on inventory size ..............................................................................................213 10.5.5 Comparison to other models .................................................................................................214 10.5.6 Lexical vowel reduction ........................................................................................................214 10.6 Typologies of vowel systems ............................................................................................................215 10.7 Conclusion .........................................................................................................................................216 11. TYPOLOGY AND THE LOCAL-RANKING HYPOTHESIS ............................................................217 11.1 Freedom of ranking ............................................................................................................................218 11.2 Combinatorial typology .....................................................................................................................219 11.3 Implicational universals .....................................................................................................................220 11.4 Case: place assimilation of nasal stops ..............................................................................................220 11.5 Optionality .........................................................................................................................................222 11.6 Problems with surface constraints .....................................................................................................222 11.7 Typology of place assimilation of nasals ..........................................................................................223 11.8 Perceptual versus acoustic faithfulness .............................................................................................225 11.9 Constraint generalization ...................................................................................................................226 11.10 Phonologization ...............................................................................................................................228 11.11 Homogeneous *GESTURE or homogeneous PARSE? .....................................................................232 11.12 Licensing ..........................................................................................................................................234 11.13 Assimilation of nasality ...................................................................................................................235 11.14 Conclusion .......................................................................................................................................236 12. CORRESPONDENCE: .........................................................................................................................237 12.1 Is perception segmental? ....................................................................................................................238 12.2 OCP-driven epenthesis ......................................................................................................................239 12.3 Horizontal and vertical correspondence ............................................................................................241 12.4 Floating features ................................................................................................................................247 12.5 Fusion ................................................................................................................................................249 12.6 Phonetic substance of epenthesis .......................................................................................................251 12.7 Subsegmental satisfaction by segmental deletion ..............................................................................251 12.8 Conclusion .........................................................................................................................................255 13. DEGREES OF SPECIFICATION ........................................................................................................257 13.1 Different feature systems for inventories and rules ...........................................................................257 13.2 Redundant features ............................................................................................................................258 13.3 Weak features ....................................................................................................................................262 13.4 The lexicon ........................................................................................................................................263 13.5 Optionality and stylistic variation ......................................................................................................265 13.6 Privative features ...............................................................................................................................265 13.7 “Trivial” underspecification ..............................................................................................................265 13.8 Invisible specifications ......................................................................................................................265 13.9 Conclusion .........................................................................................................................................266 vi CONTENTS PART III: GRAMMAR ............................................................................................................................267 14. LEARNING A PRODUCTION GRAMMAR ......................................................................................269 14.1 Grammar model .................................................................................................................................269 14.2 Learning in functional phonology .....................................................................................................271 14.2.1 The grammar .........................................................................................................................271 14.2.2 Gradual learning algorithms ..................................................................................................273 14.2.3 Three production modes ........................................................................................................274 14.2.4 Stage 1: an empty grammar ..................................................................................................275 14.2.5 Step 1: perceptual categorization and faithfulness constraints .............................................276 14.2.6 Stage 2: violated faithfulness ................................................................................................279 14.2.7 Step 2: sensorimotor learning ...............................................................................................279 14.2.8 Stage 3: faithful imitation .....................................................................................................281 14.2.9 Step 3: the learning curve ......................................................................................................282 14.2.10 Stage 4: faithfulness outranks gestural constraints .............................................................287 14.2.11 Step 4: sentence-level phonology .......................................................................................288 14.2.12 Stage 5: alternating levels of constraints ............................................................................290 14.2.13 Step 5: emergence of underlying forms ..............................................................................291 14.2.14 Stage 6: the adult phase .......................................................................................................291 14.2.15 Second-language acquisition ..............................................................................................292 14.2.16 Acoustic versus linguistic faithfulness ................................................................................292 14.2.17 Puzzles ................................................................................................................................293 14.3 Example: acquisition of tongue-root harmony ..................................................................................294 14.3.1 Universal ranking of articulatory constraints ........................................................................296 14.3.2 Universal ranking of faithfulness constraints ........................................................................297 14.3.3 Typology of tongue-root systems .........................................................................................298 14.3.4 The learning process for continuous families .......................................................................300 14.3.5 The learning of simplified Wolof ..........................................................................................301 14.3.6 An alternative Wolof: articulatory versus perceptual candidates .........................................306 14.3.7 Wolof with schwa licensing ..................................................................................................307 14.3.8 Learning unnatural local rankings ........................................................................................308 14.3.9 Real Wolof ............................................................................................................................309 14.4 Principles-and-parameters learning algorithms .................................................................................310 14.4.1 Seven possible tongue-root-harmony systems ......................................................................310 14.4.2 The Triggering Learning Algorithm .....................................................................................311 14.4.3 The subset problem ...............................................................................................................312 14.4.4 Intermezzo: the correct P&P convergence criterion .............................................................316 14.4.5 Local maxima ........................................................................................................................318 14.4.6 Relaxing conservatism or greediness ....................................................................................318 14.4.7 Genetic algorithms ................................................................................................................319 14.4.8 TLA versus GLA ..................................................................................................................319 14.5 Optimality-theoretic learning ............................................................................................................320 14.5.1 The initial state in an Optimality-theoretic grammar ............................................................320 14.5.2 Innateness ..............................................................................................................................321 14.6 Algorithm ..........................................................................................................................................322 14.7 Proof of learnability ...........................................................................................................................323 14.8 Acquisition time ................................................................................................................................327 14.9 Conclusion .........................................................................................................................................328 15. HOW WE LEARN VARIATION, OPTIONALITY, AND PROBABILITY ......................................329 15.1 Continuous ranking scale and stochastic disharmony .......................................................................330 15.2 Learning optionality in production ....................................................................................................332 15.2.1 Learning that faithfulness can be violated in an adult grammar ...........................................332 15.2.2 The minimal gradual learning step: demoting the offender ..................................................333 15.2.3 A remedy for downdrift: symmetric demotion and promotion .............................................334