WERE THIS article written in Japanese, it would be longer. A Thai translation, meanwhile, would be shorter. And yet those reading it aloud, in either language or in its original English, would finish at roughly the same time. This peculiar phenomenon is the subject of new research which finds that languages face a trade-off between complexity and speed. Those packed with information are spoken slower, while simpler ones are spoken faster. As a result, most languages are equally efficient at conveying information.

In a study published this month in Science Advances, Christophe Coupé, Yoon Mi Oh, Dan Dediu and François Pellegrino start by quantifying the information density of 17 Eurasian languages, as measured by the ease with which each syllable can be guessed based on the preceding one. Next, they record the rate at which 170 native speakers read 15 texts out loud. Finally, armed with data about the information contained in a piece of text and the speed at which it can be spoken, the authors derive the rate at which information is communicated.

The results suggest that there is an optimal range of speeds within which the brain can process information most efficiently. Speakers of simple languages pick up the pace to keep conversations brief. Speakers of complex languages exert more effort planning sentences and articulating syllables, causing discussions to drag on. Yet in both cases, information is conveyed at about the same pace. “It is like bird wings,” says Dr Coupé, one of the authors, “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.”

