Tara McAllister - PowerPoint Presentation

Slide1

Tara McAllisterMontclair State University, Montclair, New Jerseymcallistert@mail.montclair.edu

Patterns of Gestural Overlap Account for Positional Fricative Neutralization

in

Child PhonologySlide2

OutlineAn interesting data set from phonological acquisition (positional fricative gliding).

Why these child data are difficult to square with what we know about adult phonological typology.

Claim: A phonetically-based approach to phonology makes it possible to give a principled account of child-specific phenomena.

Fricative

substitution

errors are analyzed as a

phonologized

response to

a

child-specific

articulatory

limitation

on overlapping

vowel and fricative

gestures.

Positional

asymmetry emerges as the consequence of differing degrees of gestural overlap permitted in syllable-initial versus syllable-final

position (

Articulatory

Phonology).Slide3

Case study dataData were collected from a single case study subject between the ages of 3;9 and 4;3.

‘Ben’ is a monolingual English learner with severe phonological delay/disorder.

Active phonological patterns in addition to the pattern of interest:

cluster reduction

velar fronting

liquid gliding

final devoicing

debuccalization

of coda stopsSlide4

Positional neutralization of fricatives (PFN)Ben’s positional

fricative neutralization

pattern (3;9-3;10):

Syllable-initial

fricatives are realized as glides

.

[

ji

]

see

[

jaʔ

]

shark

[

joĩ

]

sewing

[

jip

]

sheep

[

jiba

]

zebra

[

wuʔ

]

food

[

wodaʔ

]

forgot

 Slide5

Positional neutralization of fricatives (PFN)Ben’s positional

fricative neutralization

pattern (3;9-3;10):

Syllable-initial

fricatives are realized as glides

.

[

ji

]

see

[

jaʔ

]

shark

[

joĩ

]

sewing

[

jip

]

sheep

[

jiba

]

zebra

[

wuʔ

]

food

[

wodaʔ

]

forgot

Syllable-final fricatives preserve faithful manner (not necessarily place or voicing).

[

mas

]

mouse

[

jʊʃ

]

fish

[

bis

]

beans

[

bʌʃbaʔ

]

Spongebob

[

babajis

]

strawberries

[

was

]

fiveSlide6

Why is PFN of interest?Not

unique to

Ben.

Numerous

studies have documented children acquiring fricatives in syllable-final before syllable-initial contexts

.

In babbling

(

Gildersleeve

-Neumann et al. 2000;

Oller

&

Eilers

, 1982; Redford et al. 1997)

In

meaningful speech

(

Dinnsen

, 1996; Edwards, 1996; Farwell, 1976; Ferguson, 1978;

Stites

, Demuth, & Kirk, 2004;

Stoel

-Gammon, 1985)

Pattern

is not universal,

but general

consensus is that fricatives in final position have a favored status in acquisition

(Edwards, 1979

).Slide7

Why is PFN of interest?PFN is a

child-specific

pattern

that reverses

a strong bias in adult phonological

typology.

In fully-developed phonologies, the

maximum range of

featural

contrasts

is realized in initial/prevocalic

position.

Example: Manner contrasts in Korean

(

Ahn

, 1998)

Stop, fricative, affricate manner allowed in onset position.

All manner contrasts neutralized to stop in coda position.

PFN belongs to set of child processes of

neutralization in strong

position

(

Dinnsen

& Farris-Trimble,

2008;

Inkelas

& Rose, 2003, 2008; McAllister, 2009

)

Challenge notion of continuity of child and adult grammars.Slide8

Neutralization in strong positionLet’s try to model PFN with a general constraint

*

Fricatives

:

In a

positional faithfulness framework

(Beckman, 1997

),

we

need a

constraint enhancing faithfulness to weak/final position

.

Ident

-manner-weak >> *

Fricatives >>

Ident

-manner

In

a positional

markedness

framework

(Smith, 2000, 2002)

,

we need a

constraint limiting

featural

contrasts in

strong

position.

*

#Fricatives

>>

Ident

-manner >> *

Fricatives

If

Ident

-manner-weak

or *

#Fricatives

are possible constraints, we should find examples of adult phonologies with

featural

neutralization in strong position.

Such grammars are in fact unattested.Slide9

Phonetics in child phonologyThe challenge: Model children’s positional neutralization without making incorrect predictions for the possible range of variation in adult grammars.

My claim: The most principled accounts of child-specific phonological patterns have adopted a phonetically-based approach to phonology

(

Dinnsen

& Farris-Trimble, 2008;

Inkelas

& Rose, 2003,

2007; McAllister, 2009;

Pater,

1997).

It is uncontroversial

that children

and

adults

experience

the physical act of

producing/perceiving

speech in different

ways.

Different

articulatory

anatomy and speech-motor control

Different perceptual sensitivitiesSlide10

Phonetically-based phonologySince children and adults are subject to different low-level phonetic pressures,

the phonetically-based model predicts divergence in their grammars as

well.

If

a speaker experiences a major change at the phonetic level

(e.g.

articulatory

maturation),

the grammar can change in response to the new phonetic pressures.

A

ccounts

for

elimination

of child-specific phonological phenomena

in the

course of

typical maturation.

I

will propose a formal

phonological model

of Ben’s PFN pattern

with roots in

a child-specific

articulatory

limitation. Slide11

Child-specific phonetic limitationsA phonetic difference between children and adults: Children have difficulty moving the tongue independent of the

jaw.

Tongue

is

motorically

complex, with many degrees of movement

freedom

(Kent, 1992).

Control of the jaw, a bilaterally hinged joint, is

motorically

simple.

In

early

stages of motor maturation, tongue moves passively with the active jaw

(

MacNeilage

& Davis, 1990

).

Even

after

some capacity for independent tongue control is acquired, acoustic measurements reveal an ongoing preference

for jaw-dominated

gestures

(Edwards,

Fourakis

, Beckman, & Fox, 1999)Slide12

Child-specific phonetic limitationsMy proposal: Preference for jaw-dominated gestures takes on

phonological status.

Move-As-Unit

:

‘Avoid jaw-independent tongue gestures.’

Move-As-Unit

can be analogized to effort-minimizing constraints in adult grammars.

Lazy

:

‘Minimize

articulatory

effort

’

(Kirchner, 2001)

MinimiseEffort

(

Flemming

, 2001)

Difference is that

Move-As-Unit

responds to a type of movement that is effortful for children but not for adults.Slide13

Why are fricatives dispreferred?

In

adult speech, fricative-containing syllables involve independent tongue and jaw control

.

In a fricative-vowel syllable

,

the jaw reaches its target before the tongue tip. (Tongue

remains high to sustain frication while jaw lowers in anticipation of the upcoming

vowel.)

In

a

vowel-fricative syllable

, the tongue tip reaches its target before the jaw

(

Mooshammer

et al., 2006

).

A

speaker who moves tongue and jaw as one unit cannot achieve this

coarticulation

.

A

typical

coarticulated

fricative-vowel or vowel-fricative transition

will thus violate

Move-As-Unit

.

Stops

and glides do not require differentiated control of tongue and jaw

(Kent, 1992). Slide14

Why the positional asymmetry?Spectrograms of Ben’s output reveal an asymmetry between initial and final fricatives:

Syllable-initial

fricatives make an immediate transition into the following vowel

.

Syllable-final

fricatives tend to be separated from the vowel by

silence and/or aspiration

noise.

Pause

separating vowel and coda fricative indicates that the gestures may not overlap at

all.

N

o

Move-As-Unit

violation.Slide15

Why the positional asymmetry?This pattern is not unique to Ben:

Target

‘nose’ produced by a typically developing child aged 2;11Slide16

Why the positional asymmetry?Target ‘kiss’ produced by a typically developing child aged

3;6

Non-overlapping vowel-fricative transitions can be observed in the speech of typically developing children.Slide17

How general is the phenomenon?Measured 237 vowel-fricative and fricative-vowel transitions elicited from 17 TD children

aged 2;11-5;7

(mean 4;7

).

A

verage

duration of silence/aspiration noise separating a vowel and a coda fricative was a substantial 88.4

ms.

In 58.8% of tokens, this interval was ≥ 25% of total vocalic interval (criterion for

preaspiration

adapted from

Gordeeva

&

Scobbie

, 2010).

This is despite the

fact that

adult American

English is thought to lack

preaspiration

of fricatives

(

Turk,

Nakai

, &

Sugahara

, 2006).

There was no significant difference in the duration of silence/aspiration before a voiced versus a voiceless fricative

.

Between

an onset fricative and the following vowel, the mean duration

of non-canonical frication noise was

20.4

ms

.

Only 4.1% met criterion for

postaspiration

.Slide18

Why the positional asymmetry?Conclusion: Child speakers produce fricative-vowel transitions with a greater degree of overlap than vowel-fricative transitions.

Lesser

Move-As-Unit

violation in the latter case.

However

, evidence that fricatives and vowels do not always overlap in final position is insufficient to account for PFN.

Necessary

to explain why a comparable non-overlapped transition is not available in syllable-initial position.Slide19

Constraints on gestural timingArticulatory Phonology:

Gestures stand in characteristic timing relations with respect to one another

(

Browman

& Goldstein, 1986 et seq

.).

Characteristic

patterns of gestural overlap

can be encoded

in Optimality-Theoretic coordination constraints

(

Gafos

, 2002).

CV-

Coord

: Align(C

, C-Center, V, Onset)

VC-

Coord

:

Align

(V

, Release, C, Target

)

Non-overlapping

transitions violate

CV-

Coord

/VC-

Coord

If

CV-

Coord

>> VC-

Coord

,

non-overlapping gestures will be penalized more heavily in initial relative to final position.Slide20

Constraints on gestural timingExperimental evidence of

syllable position effects

suggests that

CV-

Coord

>>

VC-

Coord

may

be the

default.

Degree

of overlap between a vowel and a coda consonant varies with changes in rate or prosody, but onset-vowel transitions maintain stable timing across all

conditions

(

Tuller

& Kelso, 1990, 1991).

Nam

et al. (2010): CV and VC transitions have different coupling modes and consequently different coupling

strength.

CV

coupling is in-phase (synchronous), more stable.

VC

coupling is anti-phase (offset by 180˚), less stable

.

Accounts

for developmental and typological primacy of the CV syllable shape.Slide21

Modeling Ben’s grammarPFN will occur when CV-

Coord

>>

Faith

>>

VC-

Coord

.

Harmonic Grammar

framework

turns out to be the best fit for the data, but here classic OT is used for simplicity.

Table 1. An initial fricative is replaced with a glide. Slide22

Modeling Ben’s grammarTable 2. A final fricative preserves faithful manner. Slide23

More evidence for the gestural accountBefore acquiring faithful fricatives

in all contexts,

Ben went through

an intermediate stage (3;11-4;2) in which initial fricatives were realized with an epenthetic glide:

[

sjɔ

]

saw

[

sjak

]

sock

[

sjaʊt

]

salt

[

sjaoʊ

]

share

[

sjoʊ

]

sew

[

ʃjaoʊ

]

shell

Epenthesis

is a truly unexpected repair because Ben’s phonology at the time

lacked

initial consonant clusters, including obstruent-glide clusters.

[

dɑk

]

clock

[

bun

]

spoon

[

bɑ:t

]

bread

[

dʊsɛn

]

questionSlide24

More evidence for the gestural accountArticulatory

Phonology literature

reveals several

cases where apparent epenthetic segments

are the

perceptual consequence of non-overlapping gestural coordination

.

Perceived epenthetic schwa in coda clusters in Moroccan Colloquial Arabic

(

Gafos

, 2002).

Perceived epenthetic schwa in English speakers’ attempted non-native clusters

(Davidson,

2003).

Vocal tract is briefly open during non-overlapped transition; sound produced is perceived as an epenthetic segment.

Transition

from a vowel to a coda fricative has come to feature a palatal glide in some fully-developed phonologies, e.g.

luz

, ‘light’



[

lujs

] in certain dialects of Brazilian Portuguese

(

Albano,

1999;

Operstein

,

2010).Slide25

More evidence for the gestural accountIf Ident

-Consonantal

is promoted above

CV-

Coord

,

the optimal candidate will feature a non-overlapped fricative-vowel transition instead of glide substitution.Slide26

More evidence for the gestural accountSo why don’t we hear a transitional glide in Ben’s final vowel-fricative transitions?

Visual

inspection of coda fricatives shows cessation of voicing before onset of frication

.

Preaspiration

obscures formant transitions that would create percept of epenthetic glide.

Finding

that glottal opening occurs in advance of the oral constriction for a fricative coda is entirely consistent with the gestural coordination analysis pursued here

.

Syllable

position effects affecting timing of gestures within a compound

segment (e.g. nasal

,

voiceless

obstruent

).

In

initial position, both gestures

are roughly synchronous.

In

final position,

glottal

opening gesture tends to precede the oral

constriction

(Krakow, 1999).Slide27

ConclusionsPFN is difficult to model without creating incorrect

predictions for

the range of variation

in adult

typology.

Roots in children’s

articulatory

limitations can account for absence of pattern from adult grammars.

Positional nature

of

fricative neutralization follows

from the fact that inter-gestural timing is more tightly constrained in CV than VC

contexts.

Provides new evidence that

patterns of inter-gestural coordination previously described in adult speakers are also influential in developmental

phonology.Slide28

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