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Re-evaluating the Word Token for Bilingual Speech Processing: The Case for Intonation Units

Paper · 2026 · Rebecca Pattichis, Dora LaCasse and Rena Torres Cacoullos

Summary

Code-switching (CS) metrics in NLP usually count every gap between two words as a possible switch site. The authors argue that this assumption does not fit spoken bilingual data. In speech, multi-word switches cluster at the edges of Intonation Units (IUs) and rarely occur inside them. IUs are prosodic chunks marked by cues such as pitch reset, final lengthening and pauses.

Building on their earlier IU-based work, the authors define a single IU-level version of the I-Index (Guzmán et al. 2017) that combines CS rates at IU boundaries with CS rates within IUs. They compute word-based and IU-based variants for ten bilingual datasets with multi-word CS, which range from balanced to heavily skewed language proportions. They then compare how each variant groups the datasets using hierarchical clustering.

Treating all words as eligible switch points inflates the denominator. This squeezes word-based scores into a narrow band that the usual two-significant-figure reporting cannot separate. The IU variant spreads the values out and achieves better cluster similarity. For data without prosodic transcription, the authors suggest dividing word counts by mean IU length.

Key points

  • The metric adapted is the I-Index (CS probability). Its IU version merges boundary and within-IU switches. Most switches fall at boundaries: in one dataset (recording 23 of the NMSEB corpus), 490 switches occurred at IU boundaries versus 76 within IUs.
  • Across the ten datasets, IU-based I-Index values span about 0.033–0.221, while word-based values span only about 0.010–0.058. At two significant figures, several word-based scores become indistinguishable, for example two datasets that both score 0.0228.
  • The proposed interim normalization uses mean IU length, which is roughly 3.3 words for the Spanish data and 3.9 for the English data (35,113 words / 10,634 IUs and 42,835 / 11,032).
  • All examples are drawn from NMSEB, a Spanish-English bilingual corpus recorded in New Mexico, whose transcription divides speech into IUs according to the Du Bois et al. (1993) conventions. Lone other-language items are tagged separately from multi-word CS.
  • The paper motivates the work with inconsistent CS counts reported for the same corpus (5.8% vs. 9.2% of utterances). Stated limitations include transitional continuity effects, burstiness of switches, and the need to test datasets from more diverse bilingual communities.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

Also on the byline: University of Montana.

 Fields, topics and concepts

Cite

Cite as Rebecca Pattichis, Dora LaCasse and Rena Torres Cacoullos. 2026. Re-evaluating the Word Token for Bilingual Speech Processing: The Case for Intonation Units. Computational Linguistics.

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.1162/coli.a.580

@article{pattichis2026re,
  title = {{Re-evaluating the Word Token for Bilingual Speech Processing: The Case for Intonation Units}},
  author = {Rebecca Pattichis, Dora LaCasse and Rena Torres Cacoullos},
  journal = {Computational Linguistics},
  year = {2026},
  doi = {10.1162/coli.a.580},
  url = {https://doi.org/10.1162/coli.a.580}
}

References

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