Voice Onset Time as a Parameter for Identification of Bilinguals

1. Voice Onset Time as a Parameter for Identification of Bilinguals Claire Gurski University of Western Ontario London, ON Canada

2. Introduction • A recording may be made in one language • Suspect refuses to speak that language Can voice onset time be used as a parameter for identification when cross language comparison materials are presented?

3. Background • Voice Onset Time (VOT): ‘The interval between the release of a stop consonant occlusion and the onset of the vocal-fold vibration’ and is measured ‘from acoustic displays as the time between the release burst and the first quasi-periodicity in the acoustic signal’. (Keating, 1984)  Burst VOT Beginning of Vocal-fold vibration

4. Voice Onset Time

5. VOT – Language Specific • The VOT of stop consonants [p b t d k g] differs between languages • ‘Plus/minus values of the voicing feature will have different quantitative VOT values in different languages.’ (Keating, 1984) • Eg. [p] in French has a VOT similar to a [b] in English

6. VOT and Identification? • Does a person who learns a second language acquire a native-like VOT in their second language or does their native language have an influence? • Does a person have a consistent VOT across languages regardless of differences between the two languages? • Is VOT a factor that can be used to help identify voices as being from the same speaker even if they are in two different languages?

7. Methodology - 2 studies Study 1 • Eight bilingual speakers – 4 Native French and 4 Native English • 2 paragraphs – one beginning in English and ending in French and one beginning in French and ending in English • Each paragraph read 4 times • Participants did not have the influence of other languages.

8. Participants – Study 1

9. Analysis – Study 1 • Only intervocalic stops were analyzed to eliminate the differences due to aspirated or unreleased stops • We found minimal variation between the languages in each of the paragraphs ie. English of the first paragraph and English of the second paragraph • Stats calculated based on the language of use – not its position in relation to the other language

10. Study 1 - Bilingual VOT

11. Hybrid System • For 7 out of 8 of the speakers, their VOT does not pattern with either the French or the English systems • Participants reacted similarly regardless of native language • Hybrid system created

12. bilinguals Hybrid VOT System of Bilinguals voiceless VOT positive voiced English VOT zero French voiceless voiced VOT negative

13. VOT and variation between languages • T scores – do the VOTs of the two languages of Bilingual individuals differ enough the be significantly different/distinct in the two languages? • Does their VOT pattern similarly in both languages?

14. T test significance scores Generally, the difference between the French and English VOT of Bilingual speakers does not vary considerably when they change languages

15. Questions to address • How does the VOT of Bilingual speakers compare to that of Monolingual speakers • Are there significant differences statistically that would allow for identification?

16. Methodology - 2 studies Study 2 • 4 Monolingual French Speakers • 4 Monolingual English Speakers • Read ‘The North Wind and the Sun’ 2 times in their native language • Described a comic for spontaneous production (not analyzed for this study)

17. Participants – Study 2 • The VOT of the Monolingual speakers was compared to that of the Bilingual speakers from Study 1

18. Analysis – Study 2 • Only intervocalic stops were analyzed to eliminate the differences due to aspirated or unreleased stops • Smaller samples were recorded decreasing the number of tokens • Controlled environment with Marantz recording equipment

19. Study 2 – Monolingual VOT • The VOT of Monolingual speakers follows the general patterns of French and English

20. Statistical Analysis • ANOVA tests comparing the groups – Monolingual English, French and Bilingual French/English and English/French • Are the groups significantly distinct?

21. ANOVA – Four Groups Eng, Fr, Eng/Fr, Fr/Eng • All are significant (except g – but only a limited number of tokens) • Therefore, there is a difference between the VOT of English, French, English/French Bilinguals and French/English Bilinguals

22. ANOVA – English Monolinguals with French Monolinguals • The difference in VOT of English and French Monolinguals is significant in all cases • There were no occurrences of intervocalic p so inferences are made based on the other voiceless plosives

23. ANOVA – Fr/Eng Bilinguals with Eng/Fr Bilinguals • The averages of their French and English tokens. • The only significant is b but if you look at the numbers, only participant 22 deviated and this would cause the significance. -.051924 -.054261 -.008036 -.033747 -.046522 -.054442 -.027603 -.024800 • Because there are no other significant differences this shows that the bilingual speakers pattern similarly regardless of first language

24. ANOVA – French and English of Fr/Eng and Eng/Fr Bilinguals • There are no significant differences between the French and English of Bilingual speakers • Therefore the VOT of Second language learners does not vary considerably between their two languages

25. ANOVA – Eng with Eng/Fr Bilinguals • The English Monolingual Speakers are not significantly different from the average of the English/French Bilinguals

26. ANOVA – Eng with Eng of Eng/Fr Bilinguals • The English of English/French Bilingual speakers is not significantly different from the English of monolingual speakers

27. ANOVA – Eng with Eng of Fr/Eng Bilinguals • The voiced stops are significantly different between English monolingual speakers and the English of native French speakers. • French/English bilingual speakers do not acquire a native like English VOT • If offender has a native like English VOT and suspect does not, may be an indication towards a non-identification

28. ANOVA – Fr with Fr/Eng Bilinguals • French with Fr/Eng Bilinguals is generally significant but English with Eng/Fr Bilinguals is not • The French Bilingual speakers vary from the monolingual French pattern which is not the case for their English counterparts.

29. ANOVA – Fr with Fr of Fr/Eng Bilinguals • In each case (disregard g due to limited tokens) the French VOT of the bilinguals is significantly different from the French of Monolingual speakers • This is to be expected since Bilingual Fr/Eng speakers range from Positive to negative in their VOT

30. ANOVA – Fr with Fr of Eng/Fr Bilinguals • Again we have significant differences between the French of Monolingual speakers and the French of Second language speakers • [d] and [g] are not significant but again, participant 22 who is the only outlier may be causing this insignificance

31. Conclusions • There is still much research to be done before VOT can be deemed useful in a forensic situation • Use of Hybrid system regardless of native language

32. Conclusions • Generally, VOT does not vary significantly between the languages of Bilingual speakers • This is to say that the VOTs of a /p/ spoken by a bilingual speaker in French or English will have not be significantly different • There are significant differences between the languages of Bilingual speakers and that of their Monolingual counterparts

33. Areas of Further Research • Continued Statistical Analysis • Age of language learning • Level of fluency • Multilingual or bilingual in other languages • Effects of nervousness • Reading vs. Spontaneous speech • Effects of the telephone • Canadian French affrication • Larger number of participants with similar voice qualities • Vocal Disguise