Speaking rate consistency and variability in spontaneous speech by native and non-native speakers of English

The suprasegmental characteristics of non-native speech are generally described as differing from those of native speech. Recent work has shown that in addition to speaking at overall slower rates, non-native speakers in a reading task are more variable than native speakers in their speaking rate across utterances [1]. However, read speech may contain sources of variability that are specific to processing difficulties associated with reading. In the present study, we examined speaking rate in spontaneous utterances by native speakers of Korean and Mandarin speaking English, and compared them to spontaneous utterances of native English speakers. We measured mean speaking rate within utterances, as well as the amount of rate change (slowing or speeding up of speaking rate) from utterance to utterance. Results indicate that spontaneous speech exhibits the opposite pattern of read speech; non-native speakers are less variable than native speakers in spontaneous speech. These findings are attributed to factors involving speaking style and language proficiency, and have implications for understanding the role of suprasegmental variability in speech perception and production.