Talking Faster, Saying the Same

Study finds that speech speed does not affect rate of information delivery

Businesspeople on the phone, rushing through an airport

According to a new study (“Different languages, similar encoding efficiency: comparable information rates across the human communicative niche”) published in Science Advances, languages differ in complexity and speech rate, but not in the rate of information transmission.

“Surprisingly, we find robust evidence that some languages are spoken faster than others (for example, Japanese and Spanish speakers produce about 50% more syllables per second than Vietnamese and Thai speakers). Also, some languages ‘pack’ more information per syllable due to their phonology and grammar (for example, English has about 11 times more types of syllable than are possible in Japanese)”, explains co‐author Dan Dediu. “However, more importantly, there is a trade‐off between the two such that ‘information‐light’ languages are spoken faster than the ‘information‐dense’ ones, balancing out at a rate of about 39 bits/second in all languages in our sample.”

“Crazy, isn’t it?”, asks Dr. François Pellegrino, lead author of the study and expert in linguistic complexity. These findings point at the existence of a relatively narrow optimal rate of information transmission, probably due to constraints, deeply embedded in the way our brains work, on how fast language can be processed and produced. However, there are several ways this optimum can be achieved: either you pack lots of information in each one of the few syllables coming out of your mouth, or you produce many less informative syllables.

“It is like bird wings: you may have big ones that need few beats per second or you have to really flap the little ones you got, but the result is pretty much the same in terms of flying”, adds Dr. Christophe Coupé, senior author of the study. How is this optimum achieved? The authors suggest that each language and each speaker are a tightly‐coupled system, where changes in the structure of the language (due to normal processes of language change across decades or centuries) affect its informational content, and are compensated by the language users during development. “This may be one of the few true language universals out there and it results from pressures external to language”, says Dr. Yoonmi Oh. Thus, languages and their speakers are like living systems inhabiting an ecological niche of information transmission.

The study was conducted by an international and interdisciplinary team involving scientists from France (Laboratoire Dynamique Du Langage/CNRS/Université Lyon 2 and Collegium de Lyon), New Zealand (The University of Canterbury), South Korea (Ajou University), and Hong Kong (The University of Hong Kong) in, who compared recordings in 17 languages (Basque, Cantonese, Catalan, English, Finnish, French, German, Hungarian, Italian, Japanese, Korean, Mandarin, Serbian, Spanish, Thai, Turkish, and Vietnamese)  of 15 short texts describing daily situations, read out loud by 10 native speakers per language. For each of the languages, they measured speech rate, in number of syllables per second, and the average information density of the syllables uttered. The more easily the utterance of a particular syllable may be predicted from the preceding one, the less information the former is deemed to provide.

The study is available at https://advances.sciencemag.org/content/5/9/eaaw2594

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