What speaking rates do non-native listeners prefer?

in this study we report on an experiment in which two groups of ESL participants (native Mandarin listeners and a mixed group of speakers of other languages) used a 9-point scale ranging from 'too slow' to 'too fast' to assess the appropriateness of the speech rate of narratives read by native English speakers and Mandarin learners of English. The narratives were played to listeners at their unmodified rates and at three computer-manipulated rates: all passages were adjusted to the Mean Mandarin rate, the Mean English rate, and a Reduced Rate, 10 per cent slower than the Mean Mandarin rate. In general, the modifications did not result in improvements in the ratings. However, the listeners did tend to assign better ratings to accelerated (compared with natural rate) productions from the slowest Mandarin speakers. Regression analyses projected that the Mandarin- speaking listeners would prefer the same 'ideal' rate for Mandarin -accented speech that they did for native English speech, while the other ESL learners would prefer Mandarin-accented English to be spoken at a rate slower than native English speech but faster than the Mandarin speakers' natural rate. This result may reflect a difference in processing costs for familiar and unfamiliar accents. Taken together with the results of other studies, these findings suggest that the admonition to second language learners to 'slow down' is unlikely to be a broadly beneficial strategy.