Perception of non-native clear speech: The gap between speakers’ effort and actual increase in intelligibility

Abstract

Non-native speakers are less effective at increasing intelligibility in clear speech than native speakers. However, examining only intelligibility may not fully address how non-native clear speech is perceived by listeners. We examined native English listeners’ perception of non-native English speakers’ clear speech in terms of intelligibility, comprehensibility, and speakers’ effort. Non-native English speakers produced English sentences in conversational and clear speaking styles. These productions were evaluated by 117 native English listeners. In an intelligibility task, listeners typed what they heard. In two rating tasks, listeners heard the same sentence produced by the same speaker in both a conversational and a clear speaking style. One group of listeners were asked to choose the sentence that was easier to understand (comprehensibility). Another group of listeners were asked to choose the sentence that the speaker was trying to say more clearly (speakers’ effort). The results showed that conversational-clear modifications did not result in increased intelligibility or comprehensibility. However, the rating task showed that listeners were sensitive to the speakers’ effort in the clear speaking style. These results suggest that non-native speakers’ effort to speak clearly may not necessarily result in intelligibility gains, but listeners may still be sensitive to this effort.