A paper co-authored by Professor Julián Villegas of the University of Aizu has been published in Linguistics Vanguard.
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Smiles can be conveyed to listeners via speech signals
Linguistics Vanguard, published an article co-authored by Julián Villegas titled "Smiles can be conveyed to listeners via speech signals: a case study with Japanese labiodentalization."
Can you hear a smile even when you can't see one?
When someone smiles while talking, their face isn't the only thing that changes, their speech sounds do too. A team of researchers, including Prof. Villegas, has now shown that listeners can detect a smile purely from the voice, without any visual cues.
The key lies in a subtle shift in how certain consonants are pronounced. In Japanese, smiling speakers tend to swap bilabial sounds (like [b], made with both lips) for labiodental sounds (like [v], made with the upper teeth and lower lip). The shape of the smile makes the bilabial closure harder to achieve, so the sound changes.
In two experiments using recordings from professional voice actors, participants consistently identified the "smiling" voice when it contained these labiodental sounds, even after controlling for pitch and loudness. The sound of a smile is real, and listeners can pick it up.
The study was inspired by a Japanese nurse during the COVID-19 pandemic. Wearing a mask all day, she noticed she could still signal warmth to patients by letting that [b] in daijōbu ("you'll be okay") slip into a [v], the natural sound of a smiling voice leaking through the mask.
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Name of Journal: Linguistics Vanguard
Authors: Kawahara, Shigeto, Akita, Kimi, Nagatsuka, Zen and Villegas, Julián.
Title: Smiles can be conveyed to listeners via speech signals: a case study with Japanese labiodentalization
Date of publication: Aug. 2026
Link to publication: https://doi.org/10.1515/lingvan-2026-0011
About Linguistics Vanguard
Linguistics Vanguard is an outlet for high quality articles and innovative approaches in all major areas of linguistics. This journal is published solely online and provides an accessible platform for concise, cutting-edge research articles, overviews of the state of the art in particular areas of linguistics, as well as reports on novel methods and tools in the field. With its topical breadth of coverage and quick rate of production, it is a leading platform for scientific exchange in linguistics.