-- A corpus study using logistic regression Yao Yao @NWAV37

1. Vowel alternation in the pronunciation of THE in American English -- A corpus study using logistic regression Yao Yao @NWAV37

2. 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?

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

4. 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?

5. 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

6. 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) At least three vowel variants, instead of two!

7. Preliminary analysis • Vowel name and duration [ə] [ɪ] [i]

8. Preliminary analysis • General vowel alternation pattern regarding the following segment

9. 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

10. 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)

11. 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

12. 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)

13. 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)

14. 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.

15. 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]?

16. 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

17. [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

18. 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.

19. Effect of following disfluency in ih/iy comparison • 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.

20. 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%)

21. 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%)

22. 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.

23. 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.

24. Effect of Gender

25. Effect of age

26. 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

27. 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?

28. Thanks! • Questions and comments are more than welcome…

29. 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).