1. An Articulatory Analysis of Phonological Transfer Using Real-Time MRI Joseph Tepperman, Erik Bresch, Yoon-Chul Kim, Sungbok Lee, Louis Goldstein, and Shrikanth Narayanan University of Southern California Los Angeles, USA

2. Phonological Transfer The influence of a speaker’s L1 on phonological variations in their L2 Manifested in ability (or lack thereof) to produce close contrasts Two Questions: – Do L1 and L2 speakers of English produce articulatory contrasts between close phonemes? – Do nonnative speakers demonstrate more variability in their L2 targets than in the closest L1 phonemes? Analysis Tool: real-time MRI Implications for Articulatory Modeling of Speech

3. Corpus 3 German speakers of L2 English 3 Native English speakers Real-Time MRI scans with simultaneous audio: – 22.4 frames per second, 68 x 68 pixels – 20 kHz noise-cancelled audio Stimuli: – “The Rainbow Passage” – “The North Wind and the Sun” – German translations for L2 speakers

4. Preparation Automatic processing: – Bootstrap alignment of phoneme sequence – Segmentation of vocal tract regions: Mined for two English contrasts nonexistent in German: – /d/ : /ð/ –/v/ : /w/

5. Method: An Example 3 center frames /d//ð/ absolute difference pixel-by-pixel upper lip lower lip velum organ localization: polygonal masks tongue body tongue tip mean

6. Experiments: Presence of Contrast Compare: possible contrast vs. no contrast – mean pairwise difference between close L2 phonemes vs. mean pairwise difference within one of those L2 phonemes – mean pairwise difference between close L1 and L2 phonemes vs. mean pairwise difference within that L1 phoneme

7. Experiments: Difference in Variability Compare: pairwise differences – mean pairwise difference within one L2 phoneme vs. mean pairwise difference within a contrastive L2 phoneme – mean pairwise difference within one L1 phoneme vs. mean pairwise difference within a contrastive L2 phoneme

8. Contrast Experiments 1 English speakers German speakers J2H5G1JSDHCW English /d/ : / ð / :: English /d/ : / d / whole frame≠≠≠≠≠≠ upper lip≠≠≠≠≠≠ lower lip≠≠≠≠== velum≠≠≠≠=≠ tongue body≠≠≠≠≠≠ tongue tip≠≠≠≠≠≠ English /v/ : /w/ :: English /v/ : /v/ whole frame≠≠≠≠≠≠ upper lip≠≠≠≠≠≠ lower lip≠≠≠≠≠≠ velum≠=≠=≠= tongue body≠≠≠≠≠= tongue tip≠≠≠≠== “Do L1 and L2 speakers produce close contrasts in L2 articulation?” Two-tailed t-test for difference in means, p < 0.05 Less contrast for L2 speakers Organs where we expect no contrast Possibly confused with tongue tip in automatic image segmentation Yet separable in articulatory space

9. Contrast Experiments 2 German /d/ : German / d / :: German / d / : English / ð / German /v/ : German /v/ :: German /v/ : English /w/ JSDHCWJSDHCW whole frame≠=≠≠≠≠ upper lip≠==≠≠≠ lower lip≠=≠≠≠≠ velum=≠≠≠≠≠ tongue body≠≠≠≠≠≠ tongue tip≠≠≠≠≠≠ Two-tailed t-test for difference in means, p < 0.05 “Do L2 speakers produce contrasts between close L1 and L2 phonemes?” Evidence of phonological transfer… …but it is phoneme-dependent

10. Variability Experiments 1 English speakers German speakers J2H5G1JSDHCW English / ð / : / ð / :: English /d/ : / d / whole frame >>==>> upper lip >><=>> lower lip <<<<<> velum =>>>>> tongue body <=<<<> tongue tip <<<<<> English /w/ : /w/ :: English /v/ : /v/ whole frame >>><>> upper lip >>><>> lower lip >>>==> velum ><=>>< tongue body ==><<< tongue tip <<>=<< One-tailed t-test for difference in means, p < 0.05 “Do L2 speakers produce L2 phonemes not present in their L1 with more variability than L2 phonemes present in their L1?” 1. Yes, but so do native speakers. 2. The opposite is often also true. 3. Dependent on the articulatory organ.

11. Variability Experiments 2 German /d/ : German / d / :: English / ð / : English / ð / German /v/ : German /v/ :: English /w/ : English /w/ JSDHCWJSDHCW whole frame <<><<> upper lip <<<<<> lower lip <<><<> velum <<<<<> tongue body <<><>< tongue tip <<>><< One-tailed t-test for difference in means, p < 0.05 “Do L2 speakers produce L2 phonemes not present their L1 with more variability than L1 phonemes present in their L1?” Is this speaker an outlier? The opposite: suggests they have more versatility in their L1 (and therefore more variability)

12. Conclusion Evidence of phonological transfer – L2 speakers less adept at producing close contrasts not present in their L1 Contrasts still present in L2 speech – Within some subset of articulatory organs – Close phonemes can be distinguished with articulatory models Variability seems dependent on many factors – Speaker – Articulatory organ – Target phoneme Future Work – Vowel contrasts – Manual transcripts / manual image segmentation – Intra-phoneme dynamics – More speakers