Researchers from the University of Lyon (France) conducted a comparative analysis of seven languages based on pronunciation speed. It turned out that the leader is Japanese with 7,84 syllables per second. It is followed by Spanish (7,82), French (7,18), Italian (6,99), English (6,19), German (5,97) and Chinese (5,18). Mail.ru reports this with reference to IFLScience.
A 2019 study analyzed 17 languages from Europe and Asia in terms of information per syllable. Japanese, although the fastest language, contained very little information in each syllable. This may explain why Japanese speakers speak quickly to make their sentences meaningful.
In the 1960s, studies were conducted comparing the speed of Japanese and American English. Then there were no significant differences in pronunciation speed.
