Keio Research Highlights

Japanese speakers adjust the length of consonants to convey the strength of their conviction about a subject, according to a study by Shigeto Kawahara at The Keio Institute of Culture and Linguistic Studies¹.

Unlike in English, the meaning of words in Japanese can vary dramatically depending on whether the consonants are pronounced as long or short sounds. Lengthen the 't' in the word for 'outside' (soto), for example, and you could be saying 'softly' (sotto). But consonant lengthening can also be used to emphasize the degree of meaning a speaker wishes to convey, as in the English vowel-based example, 'Thank you sooooo much for reading'. "Nobody really studies this phenomena of lengthened consonants and vowels even though it is very common in everyday speech," says Kawahara, who wanted to experimentally quantify the levels of distinction that could be conveyed through lengthening.

Kawahara and his colleague Aaron Braver at Texas Tech University selected four consonants ― t, d, s, and z. Seven undergraduate students were given two adjectives for each consonant and instructed to lengthen the consonant to indicate emphasis in the context of a sentence. For example, for 'uzai', which means 'annoying', the phrase would be 'ano koogi uzai' or 'That lecture is annoying'. Participants were asked to repeat the sentence with varying levels of emphasis, in a randomized order, either with no emphasis or with anywhere up to five levels of emphasis, as in 'ano koogi uzzzzzzai'.

The researchers used a phonetics software package called Praat to generate waveforms and spectrograms from the recordings that could be used to visually and statistically pinpoint the number of durational distinctions participants were able to convey. Kawahara was surprised by the results: "We initially thought that 3 or 4 degrees would be the most, but they managed to do 6!"

But are people able to recognize these subtle distinctions without technological intervention? In a previous study about English vowel lengthening conducted in the United States, Kawahara found that listeners are not very good at picking up on these distinctions. "The exact value of emphasis doesn't practically matter ― it is sort of a selfish thing like 'Here's what I want to say'." Kawahara plans to carry out a similar perception analysis for the Japanese consonant lengthening study.

"This is a very understudied area," he points out. "It would be interesting to branch out and examine other languages." The findings could potentially be used to improve artificial intelligence or voice recognition software.

1. Kawahara, S. & Braver, A. Durational properties of emphatically lengthened consonants in Japanese. Journal of the International Phonetic Association 44, 237-260 (2014). | article