-- A corpus study using logistic regression

Yao Yao @NWAV37

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Vowel alternation in the pronunciation of THE in American English

BACKGROUND

How do you say the word THE? [dh ah], with a schwa [dh iy], with a high front tense vowel

What is the rule for vowel alternation? Canonical rule: [dh iy] / _ [+vowel]

[dh ah] / otherwise Other stories?

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BACKGROUND

Age (Keating et al, 1994) TIMIT Corpus of read speech in English Age-dependent pronunciation

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• Younger speakers have a higher probability of using other vowels than [iy] in “the” before vowel. • No speakers above 50 yrs use other vowels than [i] before vowels.

BACKGROUND

Disfluency (Fox Tree & Clark, 1997) More [dh iy] (81%) than [dh ah] (7%) before

suspension of speech.

Ongoing sound change Age Gender? Social class? Dialect?

Online speech production Planning problem Speech rate?

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DATA

Buckeye corpus 40 speakers

All residents at Columbus, Ohio

Balanced in age and gender

1-hr interview

Transcribed at word and phone level

Dataset All tokens of the from all speakers

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PRELIMINARY COUNTS

8132 instances of the 172 different phonetic transcriptions 10 most common pronunciation cover

84.19% of the tokens Most common syllable structures

CV (N=7003); V (N=913); C (N=164) Most common vowels

[ah] (N=4426); [ih] (N=1808); [iy] (N=1130)

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At least three vowel variants, instead of two!

PRELIMINARY ANALYSIS

Vowel name and duration

[ə] [ɪ] [i] 7

PRELIMINARY ANALYSIS General vowel alternation pattern regarding

the following segment

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STUDY DESIGN

Use logistic regression to model the alternation among the three vowels ([ah], [ih], [iy]).

Predictor variables include phonological factor: following segment speaker characteristics: age, gender contextual features: disfluency, speech rate

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CODING VARIABLES

Vowel variant (outcome variable) ah: [ə] ih: [ɪ] Iy: [i]

Following segment C: Consonant V: Vowel U: Non-lingusitic

Age Y: Young (<40 yr) O: Old (>=40 yr)

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CODING VARIABLES (CONT’D)

Gender F: Female M: Male

Following Disfluency D: Disfluent

Pause Filled pause (um, uh, you know). Repetition (the) Hesitation, cutoff, extended pronunciation

F: Fluent otherwise

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CODING VARIABLES (CONT’D)

Preceding Disfluency D: Disfluent

Similar to following disfluency F: Fluent

Speed Average speed of the pause-bounded stretch (in

# of syll per second)

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SIMPLEST MODEL

[ah] vs. [iy] Exclude cases followed by non-linguistic

sounds. 5046 cases remain. Predictor variables

Block 1: following segment Block 2: age, gender, and their interaction with

following segment Block 3: speed, presence of disfluency, and their

interaction with other variables Method = Forward stepwise (conditional)

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SIMPLEST MODEL (CONT’D)

Results Following segment is most significant.

Percentage of right prediction: 80.3% 90.6% Following disfluency is also significant. No other factor or interaction appears significant.

Temporary conclusion Old/young male/female speakers respect the

canonical phonological rule equally well.

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ABOUT [IH]

Some basic facts Women produce [ih] more often than men

(28.2% vs. 21.3%) Young people produce [ih] more often than older

people (23.3% vs. 26.1%) The majority are followed by consonants

(84.5%).

Are these also the factors that would favor [ih] over [ah] or [iy]?

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A TAD MORE COMPLICATED: [IH] VS. [IY]

Exclude cases followed by non-linguistic sounds. 2675 cases remain.

Same independent variables as the previous model

Results Following segment is the most significant

condition (right prediction: 62.8% 80.7%) Following disfluency is also significant (80.7%

81.4%) Other significant factors: gender, gender X

following segment, speed X following segment 16

[IH] VS. [AH]

Exclude cases followed by non-linguistic sounds. 5747 cases remain.

Same independent variables as the previous model

Results Following segment is still significant, but the

significance is reduced (right prediction: 70.8% 71.5%)

Other significant factors: gender X following segment, age, age X gender, following disfluency

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TEMPORARY CONCLUSIONS

Most important factor is following segment, but the effect is weakest in the ah/ih model.

The presence of following disfluency also affects vowel alternation consistently, and the effect is strongest in iy/ih alternation.

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EFFECT OF FOLLOWING DISFLUENCY IN IH/IY COMPARISON

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Speaker characteristics (age, gender) and speech rate fail to enter the model for ah/iy distinction, but do show in the other two models considering the [ih] vowel. In particular, the interaction of gender and following segment shows in both models.

MOVING ON TO CASES FOLLOWED BY NON-LINGUISTIC SOUNDS

[ah] vs. [iy] Same model, but with all cases (N=5556) Significant factors

Block 1: Following segment (79.7% 89.0%) Block 2: Age X following segment, age, age X

gender. Block 3: Following disfluency, speed and their

interaction. Speed X following segment. (89.0% 89.3%)

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MOVING ON TO CASES FOLLOWED BY NON-LINGUISTIC SOUNDS

[ih] vs. [iy] Same model, but with all cases (N=2938) Significant factors

Block 1: Following segment (61.5% 78.1%) Block 2: age, gender, age X following segment,

gender X following segment. (78.1% 79.1) Block 3: Following disfluency, speed and their

interaction. (79.1% 80.7%)

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MOVING ON TO CASES FOLLOWED BY NON-LINGUISTIC SOUNDS

[ah] vs. [ih] Same model, but with all cases (N=6234) Significant factors

Block 1: Following segment (71.0% 71.6%) Block 2: age, gender, age X gender. (71.6%

71.7%) Block 3: Following disfluency X speed.

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TEMPORARY CONCLUSIONS

When all cases are included (followed by consonant, vowel, or non-linguistic sounds) Speaker characteristics enter the models, even

the one for ah/iy distinction. Following disfluency and speed continue to

contribute in all models. The ah/ih distinction is still the hardest to model.

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EFFECT OF GENDER

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EFFECT OF AGE

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GENERAL DISCUSSION

Ongoing sound change? - Yes… The new pronunciation [dh ih]

A variant form of [dh ah]? Speaker characteristics at play?

What about elongated [dh ah]? A variant form of [dh iy]? Vowel alternation duration alternation?

Disfluency and speech rate affecting the pronunciation? - Yes… Following (un)filled pauses and repetition Preceding disfluency has no effect 26

NEXT STEP

Examine the phonetic makeup of the vowels Moving from modeling vowel name distinction to

modeling continuous variables, such as formants and durations

Include more speaker variables More specific age variable Social class?

Include more contextual measures More types of disfluency Contextual predictability?

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THANKS!

Questions and comments are more than welcome…

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REFERENCES Fox Tree, J.E., Clark, H.H. (1997) . Pronouncing "the"

as "thee" to signal problems in speaking . Cognition, 62, 151-167

Keating, P., MacEachern, M., Shryock, A., Dominguez, S. (1994) . A manual for phonetic transcription: Segmentation and labeling of words in spontaneous speech . Manual written for the Linguistic Data Consortium, UCLA Working Papers in Phonetics 88, 91-120

Pitt, M.A., Dilley, L., Johnson, K., Kiesling, S., Raymond, W., Hume, E. and Fosler-Lussier, E. (2007) Buckeye Corpus of Conversational Speech (2nd release) [www.buckeyecorpus.osu.edu] Columbus, OH: Department of Psychology, Ohio State University (Distributor). 29