The study compared the efficiency of conveying information in spoken German, Mandarin Chinese, Japanese, English, French, Italian, and Spanish.
Researchers took a sample group of 59 people, who each read a sample text in their native language. The recordings were then edited to remove the pauses, and syllables were tallied in order to draw conclusions regarding the density of information communicated in each language.
Japanese was found to be the fastest spoken language, with 7.84 syllables spoken per second. Mandarin Chinese was the slowest, with the average syllabic speech rate at 5.18. However, the researchers note that in ‘faster’ languages, the individual parts of words are shorter, meaning there are more syllables. They concluded that a higher rate of syllables by no means implies that content can be transmitted more quickly.
A more comprehensive study, carried out by University of Klagenfurt linguistics professor Gertraud Fenk-Oczlon in 2010, reached similar conclusions. In this case, 51 different languages were recorded, with Indian language Tegulu found to be the fastest, and Thai the slowest.
The latest study, in more detailed form, can be found here.